Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

24 files changed, 2910 insertions, 0 deletions

diff --git a/src/seastar/demos/CMakeLists.txt b/src/seastar/demos/CMakeLists.txt
new file mode 100644
index 000000000..d24cb97a7
--- /dev/null
+++ b/src/seastar/demos/CMakeLists.txt
@@ -0,0 +1,124 @@
+#
+# This file is open source software, licensed to you under the terms
+# of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+# distributed with this work for additional information regarding copyright
+# ownership.  You may not use this file except in compliance with the License.
+#
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+#
+# Copyright (C) 2018 Scylladb, Ltd.
+#
+
+# Logical target for all demos.
+add_custom_target (demos)
+
+macro (seastar_add_demo name)
+  set (args ${ARGN})
+
+  cmake_parse_arguments (
+    parsed_args
+    ""
+    ""
+    "SOURCES"
+    ${args})
+
+  set (target demo_${name})
+  add_executable (${target} ${parsed_args_SOURCES})
+
+  target_include_directories (${target}
+    PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
+
+  target_link_libraries (${target}
+    PRIVATE
+      Boost::program_options
+      seastar_private)
+
+  set_target_properties (${target}
+    PROPERTIES
+      OUTPUT_NAME ${name}_demo)
+
+  add_dependencies (demos ${target})
+endmacro ()
+
+seastar_add_demo (block_discard
+  SOURCES block_discard_demo.cc)
+
+if (${Seastar_API_LEVEL} GREATER_EQUAL 3)
+  seastar_add_demo (coroutines
+    SOURCES coroutines_demo.cc)
+endif ()
+
+seastar_add_demo (hello-world
+  SOURCES hello-world.cc)
+
+seastar_add_demo (websocket
+  SOURCES websocket_demo.cc)
+
+seastar_add_demo (echo
+  SOURCES echo_demo.cc)
+
+seastar_add_demo (ip
+  SOURCES ip_demo.cc)
+
+seastar_add_demo (line_count
+  SOURCES line_count_demo.cc)
+
+seastar_add_demo (l3
+  SOURCES l3_demo.cc)
+
+seastar_add_demo (rpc
+  SOURCES rpc_demo.cc)
+
+seastar_add_demo (scheduling_group
+  SOURCES scheduling_group_demo.cc)
+
+seastar_add_demo (tcp
+  SOURCES tcp_demo.cc)
+
+seastar_add_demo (tcp_sctp_client
+  SOURCES tcp_sctp_client_demo.cc)
+
+seastar_add_demo (tcp_sctp_server
+  SOURCES tcp_sctp_server_demo.cc)
+
+seastar_add_demo (tls_echo_server
+  SOURCES
+    tls_echo_server.hh
+    tls_echo_server_demo.cc)
+
+seastar_add_demo (tls_simple_client
+  SOURCES
+    tls_echo_server.hh
+    tls_simple_client_demo.cc)
+
+seastar_add_demo (udp_client
+  SOURCES udp_client_demo.cc)
+
+seastar_add_demo (udp_server
+  SOURCES udp_server_demo.cc)
+
+seastar_add_demo (udp_zero_copy
+  SOURCES udp_zero_copy_demo.cc)
+
+seastar_add_demo (sharded_parameter
+  SOURCES sharded_parameter_demo.cc)
+
+seastar_add_demo (file
+  SOURCES file_demo.cc)
+
+seastar_add_demo (tutorial_examples
+  SOURCES tutorial_examples.cc)
+
+seastar_add_demo (http_client
+  SOURCES http_client_demo.cc)
diff --git a/src/seastar/demos/block_discard_demo.cc b/src/seastar/demos/block_discard_demo.cc
new file mode 100644
index 000000000..b14c5ed01
--- /dev/null
+++ b/src/seastar/demos/block_discard_demo.cc
@@ -0,0 +1,74 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#include <algorithm>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/file.hh>
+#include <seastar/core/reactor.hh>
+#include <seastar/core/seastar.hh>
+#include <seastar/core/semaphore.hh>
+#include <iostream>
+
+using namespace seastar;
+
+namespace bpo = boost::program_options;
+
+struct file_test {
+    file_test(file&& f) : f(std::move(f)) {}
+    file f;
+    semaphore sem = { 0 };
+};
+
+int main(int ac, char** av) {
+    app_template app;
+    app.add_options()
+        ("dev", bpo::value<std::string>(), "e.g. --dev /dev/sdb")
+        ;
+
+    return app.run_deprecated(ac, av, [&app] {
+        static constexpr auto max = 10000;
+        auto&& config = app.configuration();
+        auto filepath = config["dev"].as<std::string>();
+
+        return open_file_dma(filepath, open_flags::rw | open_flags::create).then([] (file f) {
+            auto ft = new file_test{std::move(f)};
+
+            // Discard asynchronously, siganl when done.
+            (void)ft->f.stat().then([ft] (struct stat st) mutable {
+                assert(S_ISBLK(st.st_mode));
+                auto offset = 0;
+                auto length = max * 4096;
+                return ft->f.discard(offset, length).then([ft] () mutable {
+                    ft->sem.signal();
+                });
+            });
+
+            // Wait and exit.
+            (void)ft->sem.wait().then([ft] () mutable {
+                return ft->f.flush();
+            }).then([ft] () mutable {
+                std::cout << "done\n";
+                delete ft;
+                engine().exit(0);
+            });
+        });
+    });
+}
diff --git a/src/seastar/demos/coroutines_demo.cc b/src/seastar/demos/coroutines_demo.cc
new file mode 100644
index 000000000..06e1ab47b
--- /dev/null
+++ b/src/seastar/demos/coroutines_demo.cc
@@ -0,0 +1,72 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2019 ScyllaDB Ltd.
+ */
+
+#include <iostream>
+
+#include <seastar/util/std-compat.hh>
+
+#ifndef SEASTAR_COROUTINES_ENABLED
+
+int main(int argc, char** argv) {
+    std::cout << "coroutines not available\n";
+    return 0;
+}
+
+#else
+
+#include <seastar/core/app-template.hh>
+#include <seastar/core/coroutine.hh>
+#include <seastar/core/fstream.hh>
+#include <seastar/core/sleep.hh>
+#include <seastar/core/seastar.hh>
+#include <seastar/core/loop.hh>
+#include <seastar/core/sstring.hh>
+#include <seastar/coroutine/parallel_for_each.hh>
+
+int main(int argc, char** argv) {
+    seastar::app_template app;
+    app.run(argc, argv, [] () -> seastar::future<> {
+        std::cout << "this is a completely useless program\nplease stand by...\n";
+        auto f = seastar::coroutine::parallel_for_each(std::vector<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }, [] (int i) -> seastar::future<> {
+            co_await seastar::sleep(std::chrono::seconds(i));
+            std::cout << i << "\n";
+        });
+
+        auto file = co_await seastar::open_file_dma("useless_file.txt", seastar::open_flags::create | seastar::open_flags::wo);
+        auto out = co_await seastar::make_file_output_stream(file);
+        seastar::sstring str = "nothing to see here, move along now\n";
+        co_await out.write(str);
+        co_await out.flush();
+        co_await out.close();
+
+        bool all_exist = true;
+        std::vector<seastar::sstring> filenames = { "useless_file.txt", "non_existing" };
+        co_await seastar::coroutine::parallel_for_each(filenames, [&all_exist] (const seastar::sstring& name) -> seastar::future<> {
+            all_exist &= co_await seastar::file_exists(name);
+        });
+        std::cout << (all_exist ? "" : "not ") << "all files exist" << std::endl;
+
+        co_await std::move(f);
+        std::cout << "done\n";
+    });
+}
+
+#endif
diff --git a/src/seastar/demos/echo_demo.cc b/src/seastar/demos/echo_demo.cc
new file mode 100644
index 000000000..d8a95a793
--- /dev/null
+++ b/src/seastar/demos/echo_demo.cc
@@ -0,0 +1,126 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ *
+ */
+
+#include <seastar/net/virtio.hh>
+#include <seastar/net/dpdk.hh>
+#include <seastar/core/reactor.hh>
+#include <seastar/net/ip.hh>
+#include <seastar/net/native-stack.hh>
+#include <iostream>
+#include <utility>
+#include <algorithm>
+
+using namespace seastar;
+using namespace net;
+
+void dump_packet(const packet& p) {
+    std::cout << "rx:";
+    auto f = p.frag(0);
+    for (unsigned i = 0; i < std::min(f.size, size_t(30)); ++i) {
+        char x[4];
+        std::sprintf(x, " %02x", uint8_t(f.base[i]));
+        std::cout << x;
+    }
+    std::cout << "\n";
+}
+
+future<> echo_packet(net::qp& netif, packet p) {
+    auto f = p.frag(0);
+    if (f.size < sizeof(eth_hdr)) {
+        return make_ready_future<>();
+    }
+    auto pos = 0;
+    auto eh = reinterpret_cast<eth_hdr*>(f.base + pos);
+    pos += sizeof(*eh);
+    *eh = ntoh(*eh);
+    if (eh->eth_proto != 0x0800) {
+        return make_ready_future<>();
+    }
+    auto iph = reinterpret_cast<ip_hdr*>(f.base + pos);
+    *iph = ntoh(*iph);
+    pos += iph->ihl * 4;
+    if (iph->ver != 4 || iph->ihl < 5 || iph->ip_proto != 1) {
+        return make_ready_future<>();
+    }
+    auto ip_len = iph->len;
+    auto icmph = reinterpret_cast<icmp_hdr*>(f.base + pos);
+    if (icmph->type != icmp_hdr::msg_type::echo_request) {
+        return make_ready_future<>();
+    }
+    auto icmp_len = ip_len - iph->ihl * 4;
+    std::swap(eh->src_mac, eh->dst_mac);
+    std::swap(iph->src_ip, iph->dst_ip);
+    icmph->type = icmp_hdr::msg_type::echo_reply;
+    icmph->csum = 0;
+    *iph = hton(*iph);
+    *eh = hton(*eh);
+    icmph->csum = ip_checksum(icmph, icmp_len);
+    iph->csum = 0;
+    iph->csum = ip_checksum(iph, iph->ihl * 4);
+    return netif.send(std::move(p));
+}
+
+#ifdef SEASTAR_HAVE_DPDK
+void usage()
+{
+    std::cout<<"Usage: echotest [-virtio|-dpdk]"<<std::endl;
+    std::cout<<"   -virtio - use virtio backend (default)"<<std::endl;
+    std::cout<<"   -dpdk   - use dpdk-pmd backend"<<std::endl;
+}
+#endif
+
+int main(int ac, char** av) {
+    std::unique_ptr<net::device> dnet;
+    net::qp* vnet;
+
+    native_stack_options opts;
+
+#ifdef SEASTAR_HAVE_DPDK
+    if (ac > 2) {
+        usage();
+        return -1;
+    }
+
+    if ((ac == 1) || !std::strcmp(av[1], "-virtio")) {
+        dnet = create_virtio_net_device(opts.virtio_opts, opts.lro);
+    } else if (!std::strcmp(av[1], "-dpdk")) {
+        dnet = create_dpdk_net_device();
+    } else {
+        usage();
+        return -1;
+    }
+#else
+    dnet = create_virtio_net_device(opts.virtio_opts, opts.lro);
+#endif // SEASTAR_HAVE_DPDK
+
+    auto qp = dnet->init_local_queue(opts, 0);
+    vnet = qp.get();
+    dnet->set_local_queue(std::move(qp));
+    future<> rx_done =
+        dnet->receive([vnet] (packet p) {
+            return echo_packet(*vnet, std::move(p));
+        });
+    engine().run();
+    return 0;
+}
+
+
diff --git a/src/seastar/demos/file_demo.cc b/src/seastar/demos/file_demo.cc
new file mode 100644
index 000000000..20f6b2cd8
--- /dev/null
+++ b/src/seastar/demos/file_demo.cc
@@ -0,0 +1,237 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright 2020 ScyllaDB
+ */
+
+
+// Demonstration of seastar::with_file
+
+#include <cstring>
+#include <limits>
+#include <random>
+
+#include <seastar/core/app-template.hh>
+
+#include <seastar/core/aligned_buffer.hh>
+#include <seastar/core/file.hh>
+#include <seastar/core/fstream.hh>
+#include <seastar/core/seastar.hh>
+#include <seastar/core/sstring.hh>
+#include <seastar/core/temporary_buffer.hh>
+#include <seastar/core/loop.hh>
+#include <seastar/core/io_intent.hh>
+#include <seastar/util/log.hh>
+#include <seastar/util/tmp_file.hh>
+
+using namespace seastar;
+
+constexpr size_t aligned_size = 4096;
+
+future<> verify_data_file(file& f, temporary_buffer<char>& rbuf, const temporary_buffer<char>& wbuf) {
+    return f.dma_read(0, rbuf.get_write(), aligned_size).then([&rbuf, &wbuf] (size_t count) {
+        assert(count == aligned_size);
+        fmt::print("    verifying {} bytes\n", count);
+        assert(!memcmp(rbuf.get(), wbuf.get(), aligned_size));
+    });
+}
+
+future<file> open_data_file(sstring meta_filename, temporary_buffer<char>& rbuf) {
+    fmt::print("    retrieving data filename from {}\n", meta_filename);
+    return with_file(open_file_dma(meta_filename, open_flags::ro), [&rbuf] (file& f) {
+        return f.dma_read(0, rbuf.get_write(), aligned_size).then([&rbuf] (size_t count) {
+            assert(count == aligned_size);
+            auto data_filename = sstring(rbuf.get());
+            fmt::print("    opening {}\n", data_filename);
+            return open_file_dma(data_filename, open_flags::ro);
+        });
+    });
+}
+
+future<> demo_with_file() {
+    fmt::print("Demonstrating with_file():\n");
+    return tmp_dir::do_with_thread([] (tmp_dir& t) {
+        auto rnd = std::mt19937(std::random_device()());
+        auto dist = std::uniform_int_distribution<int>(0, std::numeric_limits<char>::max());
+        auto wbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
+        sstring meta_filename = (t.get_path() / "meta_file").native();
+        sstring data_filename = (t.get_path() / "data_file").native();
+
+        // `with_file` is used to create/open `filename` just around the call to `dma_write`
+        auto write_to_file = [] (const sstring filename, temporary_buffer<char>& wbuf) {
+            auto count = with_file(open_file_dma(filename, open_flags::rw | open_flags::create), [&wbuf] (file& f) {
+                return f.dma_write(0, wbuf.get(), aligned_size);
+            }).get0();
+            assert(count == aligned_size);
+        };
+
+        // print the data_filename into the write buffer
+        std::fill(wbuf.get_write(), wbuf.get_write() + aligned_size, 0);
+        std::copy(data_filename.cbegin(), data_filename.cend(), wbuf.get_write());
+
+        // and write it to `meta_filename`
+        fmt::print("  writing \"{}\" into {}\n", data_filename, meta_filename);
+
+        write_to_file(meta_filename, wbuf);
+
+        // now write some random data into data_filename
+        fmt::print("  writing random data into {}\n", data_filename);
+        std::generate(wbuf.get_write(), wbuf.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); });
+
+        write_to_file(data_filename, wbuf);
+
+        // verify the data via meta_filename
+        fmt::print("  verifying data...\n");
+        auto rbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
+
+        with_file(open_data_file(meta_filename, rbuf), [&rbuf, &wbuf] (file& f) {
+            return verify_data_file(f, rbuf, wbuf);
+        }).get();
+    });
+}
+
+future<> demo_with_file_close_on_failure() {
+    fmt::print("\nDemonstrating with_file_close_on_failure():\n");
+    return tmp_dir::do_with_thread([] (tmp_dir& t) {
+        auto rnd = std::mt19937(std::random_device()());
+        auto dist = std::uniform_int_distribution<int>(0, std::numeric_limits<char>::max());
+        auto wbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
+        sstring meta_filename = (t.get_path() / "meta_file").native();
+        sstring data_filename = (t.get_path() / "data_file").native();
+
+        // with_file_close_on_failure will close the opened file only if
+        // `make_file_output_stream` returns an error. Otherwise, in the error-free path,
+        // the opened file is moved to `file_output_stream` that in-turn closes it
+        // when the stream is closed.
+        auto make_output_stream = [] (const sstring filename) {
+            return with_file_close_on_failure(open_file_dma(std::move(filename), open_flags::rw | open_flags::create), [] (file f) {
+                return make_file_output_stream(std::move(f), aligned_size);
+            });
+        };
+
+        // writes the buffer one byte at a time, to demonstrate output stream
+        auto write_to_stream = [] (output_stream<char>& o, const temporary_buffer<char>& wbuf) {
+            return seastar::do_for_each(wbuf, [&o] (char c) {
+                return o.write(&c, 1);
+            }).finally([&o] {
+                return o.close();
+            });
+        };
+
+        // print the data_filename into the write buffer
+        std::fill(wbuf.get_write(), wbuf.get_write() + aligned_size, 0);
+        std::copy(data_filename.cbegin(), data_filename.cend(), wbuf.get_write());
+
+        // and write it to `meta_filename`
+        fmt::print("  writing \"{}\" into {}\n", data_filename, meta_filename);
+
+        // with_file_close_on_failure will close the opened file only if
+        // `make_file_output_stream` returns an error. Otherwise, in the error-free path,
+        // the opened file is moved to `file_output_stream` that in-turn closes it
+        // when the stream is closed.
+        output_stream<char> o = make_output_stream(meta_filename).get0();
+
+        write_to_stream(o, wbuf).get();
+
+        // now write some random data into data_filename
+        fmt::print("  writing random data into {}\n", data_filename);
+        std::generate(wbuf.get_write(), wbuf.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); });
+
+        o = make_output_stream(data_filename).get0();
+
+        write_to_stream(o, wbuf).get();
+
+        // verify the data via meta_filename
+        fmt::print("  verifying data...\n");
+        auto rbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
+
+        with_file(open_data_file(meta_filename, rbuf), [&rbuf, &wbuf] (file& f) {
+            return verify_data_file(f, rbuf, wbuf);
+        }).get();
+    });
+}
+
+static constexpr size_t half_aligned_size = aligned_size / 2;
+
+future<> demo_with_io_intent() {
+    fmt::print("\nDemonstrating demo_with_io_intent():\n");
+    return tmp_dir::do_with_thread([] (tmp_dir& t) {
+        sstring filename = (t.get_path() / "testfile.tmp").native();
+        auto f = open_file_dma(filename, open_flags::rw | open_flags::create).get0();
+
+        auto rnd = std::mt19937(std::random_device()());
+        auto dist = std::uniform_int_distribution<int>(0, std::numeric_limits<char>::max());
+
+        auto wbuf = temporary_buffer<char>::aligned(aligned_size, aligned_size);
+        fmt::print("  writing random data into {}\n", filename);
+        std::generate(wbuf.get_write(), wbuf.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); });
+
+        f.dma_write(0, wbuf.get(), aligned_size).get();
+
+        auto wbuf_n = temporary_buffer<char>::aligned(aligned_size, aligned_size);
+        fmt::print("  starting to overwrite {} with other random data in two steps\n", filename);
+        std::generate(wbuf_n.get_write(), wbuf_n.get_write() + aligned_size, [&dist, &rnd] { return dist(rnd); });
+
+        io_intent intent;
+        auto f1 = f.dma_write(0, wbuf_n.get(), half_aligned_size);
+        auto f2 = f.dma_write(half_aligned_size, wbuf_n.get() + half_aligned_size, half_aligned_size, default_priority_class(), &intent);
+
+        fmt::print("  cancel the 2nd overwriting\n");
+        intent.cancel();
+
+        fmt::print("  wait for overwriting IOs to complete\n");
+        f1.get();
+
+        bool cancelled = false;
+        try {
+            f2.get();
+            // The file::dma_write doesn't preemt, but if it
+            // suddenly will, the 2nd write will pass before
+            // the intent would be cancelled
+            fmt::print("    2nd write won the race with cancellation\n");
+        } catch (cancelled_error& ex) {
+            cancelled = true;
+        }
+
+        fmt::print("  verifying data...\n");
+        auto rbuf = allocate_aligned_buffer<unsigned char>(aligned_size, aligned_size);
+        f.dma_read(0, rbuf.get(), aligned_size).get();
+
+        // First part of the buffer must coincide with the overwritten data
+        assert(!memcmp(rbuf.get(), wbuf_n.get(), half_aligned_size));
+
+        if (cancelled) {
+            // Second part -- with the old data ...
+            assert(!memcmp(rbuf.get() + half_aligned_size, wbuf.get() + half_aligned_size, half_aligned_size));
+        } else {
+            // ... or with new if the cancellation didn't happen
+            assert(!memcmp(rbuf.get() + half_aligned_size, wbuf.get() + half_aligned_size, half_aligned_size));
+        }
+    });
+}
+
+int main(int ac, char** av) {
+    app_template app;
+    return app.run(ac, av, [] {
+        return demo_with_file().then([] {
+            return demo_with_file_close_on_failure().then([] {
+                return demo_with_io_intent();
+            });
+        });
+    });
+}
diff --git a/src/seastar/demos/hello-world.cc b/src/seastar/demos/hello-world.cc
new file mode 100644
index 000000000..e010ff26b
--- /dev/null
+++ b/src/seastar/demos/hello-world.cc
@@ -0,0 +1,35 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2022 ScyllaDB Ltd.
+ */
+
+#include <seastar/core/app-template.hh>
+#include <seastar/core/seastar.hh>
+#include <seastar/util/log.hh>
+
+using namespace seastar;
+logger applog("app");
+
+int main(int argc, char** argv) {
+    seastar::app_template app;
+    app.run(argc, argv, [] () -> future<> {
+        applog.info("Hello world!");
+        return make_ready_future<>();
+    });
+}
diff --git a/src/seastar/demos/http_client_demo.cc b/src/seastar/demos/http_client_demo.cc
new file mode 100644
index 000000000..c1db64468
--- /dev/null
+++ b/src/seastar/demos/http_client_demo.cc
@@ -0,0 +1,111 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2022 ScyllaDB Ltd.
+ */
+
+#include <seastar/core/app-template.hh>
+#include <seastar/core/reactor.hh>
+#include <seastar/core/shared_ptr.hh>
+#include <seastar/core/iostream.hh>
+#include <seastar/core/fstream.hh>
+#include <seastar/core/thread.hh>
+#include <seastar/http/client.hh>
+#include <seastar/http/request.hh>
+#include <seastar/http/reply.hh>
+#include <seastar/net/inet_address.hh>
+#include <seastar/net/dns.hh>
+#include <seastar/net/tls.hh>
+
+using namespace seastar;
+namespace bpo = boost::program_options;
+
+struct printer {
+    future<consumption_result<char>> operator() (temporary_buffer<char> buf) {
+        if (buf.empty()) {
+            return make_ready_future<consumption_result<char>>(stop_consuming(std::move(buf)));
+        }
+        fmt::print("{}", sstring(buf.get(), buf.size()));
+        return make_ready_future<consumption_result<char>>(continue_consuming());
+    }
+};
+
+int main(int ac, char** av) {
+    app_template app;
+    app.add_options()
+            ("https", bpo::bool_switch(), "Use HTTPS on port 443 (if off -- use HTTP on port 80)")
+            ("host", bpo::value<std::string>(), "Host to connect")
+            ("path", bpo::value<std::string>(), "Path to query upon")
+            ("method", bpo::value<std::string>()->default_value("GET"), "Method to use")
+            ("file", bpo::value<std::string>(), "File to get body from (no body if missing)")
+    ;
+
+
+    return app.run(ac, av, [&] {
+        auto&& config = app.configuration();
+        auto host = config["host"].as<std::string>();
+        auto path = config["path"].as<std::string>();
+        auto method = config["method"].as<std::string>();
+        auto body = config.count("file") == 0 ? std::string("") : config["file"].as<std::string>();
+        auto https = config["https"].as<bool>();
+
+        return seastar::async([=] {
+            net::hostent e = net::dns::get_host_by_name(host, net::inet_address::family::INET).get0();
+            auto make_socket = [=] () -> connected_socket {
+                if (!https) {
+                    socket_address local = socket_address(::sockaddr_in{AF_INET, INADDR_ANY, {0}});
+                    ipv4_addr addr(e.addr_list.front(), 80);
+                    fmt::print("{} {}:80{}\n", method, e.addr_list.front(), path);
+                    return connect(make_ipv4_address(addr), local, transport::TCP).get0();
+                } else {
+                    auto certs = ::make_shared<tls::certificate_credentials>();
+                    certs->set_system_trust().get();
+                    socket_address remote = socket_address(e.addr_list.front(), 443);
+                    fmt::print("{} {}:443{}\n", method, e.addr_list.front(), path);
+                    return tls::connect(certs, remote, host).get0();
+                }
+            };
+
+            connected_socket s = make_socket();
+            http::experimental::connection conn(std::move(s));
+            auto req = http::request::make(method, host, path);
+            if (body != "") {
+                future<file> f = open_file_dma(body, open_flags::ro);
+                req.write_body("txt", [ f = std::move(f) ] (output_stream<char>&& out) mutable {
+                    return seastar::async([f = std::move(f), out = std::move(out)] () mutable {
+                        auto in = make_file_input_stream(f.get0());
+                        copy(in, out).get();
+                        out.flush().get();
+                        out.close().get();
+                        in.close().get();
+                    });
+                });
+            }
+            http::reply rep = conn.make_request(std::move(req)).get0();
+
+            fmt::print("Reply status {}\n--------8<--------\n", rep._status);
+            auto in = conn.in(rep);
+            in.consume(printer{}).get();
+            in.close().get();
+
+            conn.close().get();
+        }).handle_exception([](auto ep) {
+            fmt::print("Error: {}", ep);
+        });
+    });
+}
diff --git a/src/seastar/demos/ip_demo.cc b/src/seastar/demos/ip_demo.cc
new file mode 100644
index 000000000..c58efc29b
--- /dev/null
+++ b/src/seastar/demos/ip_demo.cc
@@ -0,0 +1,47 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#include <seastar/net/arp.hh>
+#include <seastar/net/ip.hh>
+#include <seastar/net/net.hh>
+#include <seastar/core/reactor.hh>
+#include <seastar/net/virtio.hh>
+#include <seastar/net/native-stack.hh>
+#include <seastar/core/aligned_buffer.hh>
+
+using namespace seastar;
+using namespace net;
+
+int main(int ac, char** av) {
+    native_stack_options opts;
+
+    auto vnet = create_virtio_net_device(opts.virtio_opts, opts.lro);
+    vnet->set_local_queue(vnet->init_local_queue(opts, 0));
+
+    interface netif(std::move(vnet));
+    ipv4 inet(&netif);
+    inet.set_host_address(ipv4_address("192.168.122.2"));
+    engine().run();
+    return 0;
+}
+
+
+
diff --git a/src/seastar/demos/l3_demo.cc b/src/seastar/demos/l3_demo.cc
new file mode 100644
index 000000000..7813e109d
--- /dev/null
+++ b/src/seastar/demos/l3_demo.cc
@@ -0,0 +1,49 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#include <seastar/net/net.hh>
+#include <seastar/core/reactor.hh>
+#include <seastar/net/virtio.hh>
+#include <seastar/net/native-stack.hh>
+#include <iostream>
+
+using namespace seastar;
+using namespace net;
+
+void dump_arp_packets(l3_protocol& proto) {
+    // FIXME: ignored future
+    (void)proto.receive([] (packet p, ethernet_address from) {
+        std::cout << "seen arp packet\n";
+        return make_ready_future<>();
+    }, [] (forward_hash& out_hash_data, packet& p, size_t off) {return false;});
+}
+
+int main(int ac, char** av) {
+    native_stack_options opts;
+
+    auto vnet = create_virtio_net_device(opts.virtio_opts, opts.lro);
+    interface netif(std::move(vnet));
+    l3_protocol arp(&netif, eth_protocol_num::arp, []{ return std::optional<l3_protocol::l3packet>(); });
+    dump_arp_packets(arp);
+    engine().run();
+    return 0;
+}
+
diff --git a/src/seastar/demos/line_count_demo.cc b/src/seastar/demos/line_count_demo.cc
new file mode 100644
index 000000000..eab4609ec
--- /dev/null
+++ b/src/seastar/demos/line_count_demo.cc
@@ -0,0 +1,85 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2015 Cloudius Systems, Ltd.
+ */
+
+// Demonstration of file_input_stream.  Don't expect stellar performance
+// since no read-ahead or caching is done yet.
+
+#include <seastar/core/fstream.hh>
+#include <seastar/core/seastar.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/shared_ptr.hh>
+#include <fmt/printf.h>
+#include <algorithm>
+#include <iostream>
+
+using namespace seastar;
+
+struct reader {
+public:
+    reader(file f)
+            : is(make_file_input_stream(std::move(f), file_input_stream_options{1 << 16, 1})) {
+    }
+
+    input_stream<char> is;
+    size_t count = 0;
+
+    // for input_stream::consume():
+    using unconsumed_remainder = std::optional<temporary_buffer<char>>;
+    future<unconsumed_remainder> operator()(temporary_buffer<char> data) {
+        if (data.empty()) {
+            return make_ready_future<unconsumed_remainder>(std::move(data));
+        } else {
+            count += std::count(data.begin(), data.end(), '\n');
+            // FIXME: last line without \n?
+            return make_ready_future<unconsumed_remainder>();
+        }
+    }
+};
+
+int main(int ac, char** av) {
+    app_template app;
+    namespace bpo = boost::program_options;
+    app.add_positional_options({
+        { "file", bpo::value<std::string>(), "File to process", 1 },
+    });
+    return app.run(ac, av, [&app] {
+        auto fname = app.configuration()["file"].as<std::string>();
+        return open_file_dma(fname, open_flags::ro).then([] (file f) {
+            auto r = make_shared<reader>(std::move(f));
+            return r->is.consume(*r).then([r] {
+               fmt::print("{:d} lines\n", r->count);
+               return r->is.close().then([r] {});
+            });
+        }).then_wrapped([] (future<> f) -> future<int> {
+            try {
+                f.get();
+                return make_ready_future<int>(0);
+            } catch (std::exception& ex) {
+                std::cout << ex.what() << "\n";
+                return make_ready_future<int>(1);
+            } catch (...) {
+                std::cout << "unknown exception\n";
+                return make_ready_future<int>(1);
+            }
+        });
+    });
+}
+
diff --git a/src/seastar/demos/rpc_demo.cc b/src/seastar/demos/rpc_demo.cc
new file mode 100644
index 000000000..d46cd07ec
--- /dev/null
+++ b/src/seastar/demos/rpc_demo.cc
@@ -0,0 +1,299 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright 2015 Cloudius Systems
+ */
+#include <cmath>
+#include <seastar/core/reactor.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/rpc/rpc.hh>
+#include <seastar/core/sleep.hh>
+#include <seastar/rpc/lz4_compressor.hh>
+#include <seastar/util/log.hh>
+#include <seastar/core/loop.hh>
+
+using namespace seastar;
+
+struct serializer {
+};
+
+template <typename T, typename Output>
+inline
+void write_arithmetic_type(Output& out, T v) {
+    static_assert(std::is_arithmetic<T>::value, "must be arithmetic type");
+    return out.write(reinterpret_cast<const char*>(&v), sizeof(T));
+}
+
+template <typename T, typename Input>
+inline
+T read_arithmetic_type(Input& in) {
+    static_assert(std::is_arithmetic<T>::value, "must be arithmetic type");
+    T v;
+    in.read(reinterpret_cast<char*>(&v), sizeof(T));
+    return v;
+}
+
+template <typename Output>
+inline void write(serializer, Output& output, int32_t v) { return write_arithmetic_type(output, v); }
+template <typename Output>
+inline void write(serializer, Output& output, uint32_t v) { return write_arithmetic_type(output, v); }
+template <typename Output>
+inline void write(serializer, Output& output, int64_t v) { return write_arithmetic_type(output, v); }
+template <typename Output>
+inline void write(serializer, Output& output, uint64_t v) { return write_arithmetic_type(output, v); }
+template <typename Output>
+inline void write(serializer, Output& output, double v) { return write_arithmetic_type(output, v); }
+template <typename Input>
+inline int32_t read(serializer, Input& input, rpc::type<int32_t>) { return read_arithmetic_type<int32_t>(input); }
+template <typename Input>
+inline uint32_t read(serializer, Input& input, rpc::type<uint32_t>) { return read_arithmetic_type<uint32_t>(input); }
+template <typename Input>
+inline uint64_t read(serializer, Input& input, rpc::type<uint64_t>) { return read_arithmetic_type<uint64_t>(input); }
+template <typename Input>
+inline uint64_t read(serializer, Input& input, rpc::type<int64_t>) { return read_arithmetic_type<int64_t>(input); }
+template <typename Input>
+inline double read(serializer, Input& input, rpc::type<double>) { return read_arithmetic_type<double>(input); }
+
+template <typename Output>
+inline void write(serializer, Output& out, const sstring& v) {
+    write_arithmetic_type(out, uint32_t(v.size()));
+    out.write(v.c_str(), v.size());
+}
+
+template <typename Input>
+inline sstring read(serializer, Input& in, rpc::type<sstring>) {
+    auto size = read_arithmetic_type<uint32_t>(in);
+    sstring ret = uninitialized_string(size);
+    in.read(ret.data(), size);
+    return ret;
+}
+
+namespace bpo = boost::program_options;
+using namespace std::chrono_literals;
+
+class mycomp : public rpc::compressor::factory {
+    const sstring _name = "LZ4";
+public:
+    virtual const sstring& supported() const override {
+        fmt::print("supported called\n");
+        return _name;
+    }
+    virtual std::unique_ptr<rpc::compressor> negotiate(sstring feature, bool is_server) const override {
+        fmt::print("negotiate called with {}\n", feature);
+        return feature == _name ? std::make_unique<rpc::lz4_compressor>() : nullptr;
+    }
+};
+
+int main(int ac, char** av) {
+    app_template app;
+    app.add_options()
+                    ("port", bpo::value<uint16_t>()->default_value(10000), "RPC server port")
+                    ("server", bpo::value<std::string>(), "Server address")
+                    ("compress", bpo::value<bool>()->default_value(false), "Compress RPC traffic");
+    std::cout << "start ";
+    rpc::protocol<serializer> myrpc(serializer{});
+    static std::unique_ptr<rpc::protocol<serializer>::server> server;
+    static std::unique_ptr<rpc::protocol<serializer>::client> client;
+    static double x = 30.0;
+
+    static logger log("rpc_demo");
+    myrpc.set_logger(&log);
+
+    return app.run_deprecated(ac, av, [&] {
+        auto&& config = app.configuration();
+        uint16_t port = config["port"].as<uint16_t>();
+        bool compress = config["compress"].as<bool>();
+        static mycomp mc;
+        auto test1 = myrpc.register_handler(1, [x = 0](int i) mutable { fmt::print("test1 count {:d} got {:d}\n", ++x, i); });
+        auto test2 = myrpc.register_handler(2, [](int a, int b){ fmt::print("test2 got {:d} {:d}\n", a, b); return make_ready_future<int>(a+b); });
+        auto test3 = myrpc.register_handler(3, [](double x){ fmt::print("test3 got {:f}\n", x); return std::make_unique<double>(sin(x)); });
+        auto test4 = myrpc.register_handler(4, [](){ fmt::print("test4 throw!\n"); throw std::runtime_error("exception!"); });
+        auto test5 = myrpc.register_handler(5, [](){ fmt::print("test5 no wait\n"); return rpc::no_wait; });
+        auto test6 = myrpc.register_handler(6, [](const rpc::client_info& info, int x){ fmt::print("test6 client {}, {:d}\n", inet_ntoa(info.addr.as_posix_sockaddr_in().sin_addr), x); });
+        auto test8 = myrpc.register_handler(8, [](){ fmt::print("test8 sleep for 2 sec\n"); return sleep(2s); });
+        auto test13 = myrpc.register_handler(13, [](){ fmt::print("test13 sleep for 1 msec\n"); return sleep(1ms); });
+        auto test_message_to_big = myrpc.register_handler(14, [](sstring payload){ fmt::print("test message to bit, should not get here"); });
+
+        if (config.count("server")) {
+            std::cout << "client" << std::endl;
+            auto test7 = myrpc.make_client<long (long a, long b)>(7);
+            auto test9 = myrpc.make_client<long (long a, long b)>(9); // do not send optional
+            auto test9_1 = myrpc.make_client<long (long a, long b, int c)>(9); // send optional
+            auto test9_2 = myrpc.make_client<long (long a, long b, int c, long d)>(9); // send more data than handler expects
+            auto test10 = myrpc.make_client<long ()>(10); // receive less then replied
+            auto test10_1 = myrpc.make_client<future<rpc::tuple<long, int>> ()>(10); // receive all
+            auto test11 = myrpc.make_client<future<rpc::tuple<long, rpc::optional<int>>> ()>(11); // receive more then replied
+            auto test12 = myrpc.make_client<void (int sleep_ms, sstring payload)>(12); // large payload vs. server limits
+            auto test_nohandler = myrpc.make_client<void ()>(100000000); // non existing verb
+            auto test_nohandler_nowait = myrpc.make_client<rpc::no_wait_type ()>(100000000); // non existing verb, no_wait call
+            rpc::client_options co;
+            if (compress) {
+                co.compressor_factory = &mc;
+            }
+
+            client = std::make_unique<rpc::protocol<serializer>::client>(myrpc, co, ipv4_addr{config["server"].as<std::string>()});
+
+            auto f = test8(*client, 1500ms).then_wrapped([](future<> f) {
+                try {
+                    f.get();
+                    printf("test8 should not get here!\n");
+                } catch (rpc::timeout_error&) {
+                    printf("test8 timeout!\n");
+                }
+            });
+            for (auto i = 0; i < 100; i++) {
+                fmt::print("iteration={:d}\n", i);
+                (void)test1(*client, 5).then([] (){ fmt::print("test1 ended\n");});
+                (void)test2(*client, 1, 2).then([] (int r) { fmt::print("test2 got {:d}\n", r); });
+                (void)test3(*client, x).then([](double x) { fmt::print("sin={:f}\n", x); });
+                (void)test4(*client).then_wrapped([](future<> f) {
+                    try {
+                        f.get();
+                        fmt::print("test4 your should not see this!\n");
+                    } catch (std::runtime_error& x){
+                        fmt::print("test4 {}\n", x.what());
+                    }
+                });
+                (void)test5(*client).then([] { fmt::print("test5 no wait ended\n"); });
+                (void)test6(*client, 1).then([] { fmt::print("test6 ended\n"); });
+                (void)test7(*client, 5, 6).then([] (long r) { fmt::print("test7 got {:d}\n", r); });
+                (void)test9(*client, 1, 2).then([] (long r) { fmt::print("test9 got {:d}\n", r); });
+                (void)test9_1(*client, 1, 2, 3).then([] (long r) { fmt::print("test9.1 got {:d}\n", r); });
+                (void)test9_2(*client, 1, 2, 3, 4).then([] (long r) { fmt::print("test9.2 got {:d}\n", r); });
+                (void)test10(*client).then([] (long r) { fmt::print("test10 got {:d}\n", r); });
+                (void)test10_1(*client).then([] (rpc::tuple<long, int> r) { fmt::print("test10_1 got {:d} and {:d}\n", std::get<0>(r), std::get<1>(r)); });
+                (void)test11(*client).then([] (rpc::tuple<long, rpc::optional<int> > r) { fmt::print("test11 got {:d} and {:d}\n", std::get<0>(r), bool(std::get<1>(r))); });
+                (void)test_nohandler(*client).then_wrapped([](future<> f) {
+                    try {
+                        f.get();
+                        fmt::print("test_nohandler your should not see this!\n");
+                    } catch (rpc::unknown_verb_error& x){
+                        fmt::print("test_nohandle no such verb\n");
+                    } catch (...) {
+                        fmt::print("incorrect exception!\n");
+                    }
+                });
+                (void)test_nohandler_nowait(*client);
+                auto c = make_lw_shared<rpc::cancellable>();
+                (void)test13(*client, *c).then_wrapped([](future<> f) {
+                    try {
+                        f.get();
+                        fmt::print("test13 shold not get here\n");
+                    } catch(rpc::canceled_error&) {
+                        fmt::print("test13 canceled\n");
+                    } catch(...) {
+                        fmt::print("test13 wrong exception\n");
+                    }
+                });
+                c->cancel();
+                (void)test13(*client, *c).then_wrapped([](future<> f) {
+                    try {
+                        f.get();
+                        fmt::print("test13 shold not get here\n");
+                    } catch(rpc::canceled_error&) {
+                        fmt::print("test13 canceled\n");
+                    } catch(...) {
+                        fmt::print("test13 wrong exception\n");
+                    }
+                });
+                (void)sleep(500us).then([c] { c->cancel(); });
+                (void)test_message_to_big(*client, uninitialized_string(10'000'001)).then_wrapped([](future<> f) {
+                    try {
+                        f.get();
+                        fmt::print("test message to big shold not get here\n");
+                    } catch(std::runtime_error& err) {
+                        fmt::print("test message to big get error {}\n", err.what());
+                    } catch(...) {
+                        fmt::print("test message to big wrong exception\n");
+                    }
+                });
+            }
+            // delay a little for a time-sensitive test
+            (void)sleep(400ms).then([test12] () mutable {
+                // server is configured for 10MB max, throw 25MB worth of requests at it.
+                auto now = rpc::rpc_clock_type::now();
+                return parallel_for_each(boost::irange(0, 25), [test12, now] (int idx) mutable {
+                    return test12(*client, 100, uninitialized_string(1'000'000)).then([idx, now] {
+                        auto later = rpc::rpc_clock_type::now();
+                        auto delta = std::chrono::duration_cast<std::chrono::milliseconds>(later - now);
+                        fmt::print("idx {:d} completed after {:d} ms\n", idx, delta.count());
+                    });
+                }).then([now] {
+                    auto later = rpc::rpc_clock_type::now();
+                    auto delta = std::chrono::duration_cast<std::chrono::milliseconds>(later - now);
+                    fmt::print("test12 completed after {:d} ms (should be ~300)\n", delta.count());
+                });
+            });
+            (void)f.finally([] {
+                return sleep(1s).then([] {
+                    return client->stop().then([] {
+                        return engine().exit(0);
+                    });
+                });
+            });
+        } else {
+            std::cout << "server on port " << port << std::endl;
+            myrpc.register_handler(7, [](long a, long b) mutable {
+                auto p = make_lw_shared<promise<>>();
+                auto t = make_lw_shared<timer<>>();
+                fmt::print("test7 got {:d} {:d}\n", a, b);
+                auto f = p->get_future().then([a, b, t] {
+                    fmt::print("test7 calc res\n");
+                    return a - b;
+                });
+                t->set_callback([p = std::move(p)] () mutable { p->set_value(); });
+                t->arm(1s);
+                return f;
+            });
+            myrpc.register_handler(9, [] (long a, long b, rpc::optional<int> c) {
+                long r = 2;
+                fmt::print("test9 got {:d} {:d} ", a, b);
+                if (c) {
+                    fmt::print("{:d}", c.value());
+                    r++;
+                }
+                fmt::print("\n");
+                return r;
+            });
+            myrpc.register_handler(10, [] {
+                fmt::print("test 10\n");
+                return make_ready_future<rpc::tuple<long, int>>(rpc::tuple<long, int>(1, 2));
+            });
+            myrpc.register_handler(11, [] {
+                fmt::print("test 11\n");
+                return 1ul;
+            });
+            myrpc.register_handler(12, [] (int sleep_ms, sstring payload) {
+                return sleep(std::chrono::milliseconds(sleep_ms)).then([] {
+                    return make_ready_future<>();
+                });
+            });
+
+            rpc::resource_limits limits;
+            limits.bloat_factor = 1;
+            limits.basic_request_size = 0;
+            limits.max_memory = 10'000'000;
+            rpc::server_options so;
+            if (compress) {
+                so.compressor_factory = &mc;
+            }
+            server = std::make_unique<rpc::protocol<serializer>::server>(myrpc, so, ipv4_addr{port}, limits);
+        }
+    });
+
+}
diff --git a/src/seastar/demos/scheduling_group_demo.cc b/src/seastar/demos/scheduling_group_demo.cc
new file mode 100644
index 000000000..9ea9edc1b
--- /dev/null
+++ b/src/seastar/demos/scheduling_group_demo.cc
@@ -0,0 +1,186 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2016 Scylla DB Ltd
+ */
+
+
+#include <seastar/core/app-template.hh>
+#include <seastar/core/future.hh>
+#include <seastar/core/scheduling.hh>
+#include <seastar/core/thread.hh>
+#include <seastar/core/loop.hh>
+#include <seastar/core/when_all.hh>
+#include <seastar/core/with_scheduling_group.hh>
+#include <seastar/core/condition-variable.hh>
+#include <seastar/util/defer.hh>
+#include <fmt/printf.h>
+#include <chrono>
+#include <cmath>
+#include <boost/range/irange.hpp>
+
+using namespace seastar;
+using namespace std::chrono_literals;
+
+template <typename Func, typename Duration>
+future<>
+compute_intensive_task(Duration duration, unsigned& counter, Func func) {
+    auto end = std::chrono::steady_clock::now() + duration;
+    while (std::chrono::steady_clock::now() < end) {
+        func();
+    }
+    ++counter;
+    return make_ready_future<>();
+}
+
+future<>
+heavy_task(unsigned& counter) {
+    return compute_intensive_task(1ms, counter, [] {
+        static thread_local double x = 1;
+        x = std::exp(x) / 3;
+    });
+}
+
+future<>
+light_task(unsigned& counter) {
+    return compute_intensive_task(100us, counter, [] {
+        static thread_local double x = 0.1;
+        x = std::log(x + 1);
+    });
+}
+
+future<>
+medium_task(unsigned& counter) {
+    return compute_intensive_task(400us, counter, [] {
+        static thread_local double x = 0.1;
+        x = std::cos(x);
+    });
+}
+
+using done_func = std::function<bool ()>;
+
+future<>
+run_compute_intensive_tasks(seastar::scheduling_group sg, done_func done, unsigned concurrency, unsigned& counter, std::function<future<> (unsigned& counter)> task) {
+    return seastar::async([task = std::move(task), sg, concurrency, done, &counter] () mutable {
+        while (!done()) {
+            parallel_for_each(boost::irange(0u, concurrency), [task, sg, &counter] (unsigned i) mutable {
+                return with_scheduling_group(sg, [task, &counter] {
+                    return task(counter);
+                });
+            }).get();
+            thread::maybe_yield();
+        }
+    });
+}
+
+future<>
+run_compute_intensive_tasks_in_threads(seastar::scheduling_group sg, done_func done, unsigned concurrency, unsigned& counter, std::function<future<> (unsigned& counter)> task) {
+    auto attr = seastar::thread_attributes();
+    attr.sched_group = sg;
+    return parallel_for_each(boost::irange(0u, concurrency), [attr, done, &counter, task] (unsigned i) {
+        return seastar::async(attr, [done, &counter, task] {
+            while (!done()) {
+                task(counter).get();
+                thread::maybe_yield();
+            }
+        });
+    });
+}
+
+future<>
+run_with_duty_cycle(float utilization, std::chrono::steady_clock::duration period, done_func done, std::function<future<> (done_func done)> task) {
+    return seastar::async([=] {
+        bool duty_toggle = true;
+        auto t0 = std::chrono::steady_clock::now();
+        condition_variable cv;
+        timer<> tmr_on([&] { duty_toggle = true; cv.signal(); });
+        timer<> tmr_off([&] { duty_toggle = false; });
+        tmr_on.arm(t0, period);
+        tmr_off.arm(t0 + std::chrono::duration_cast<decltype(t0)::duration>(period * utilization), period);
+        auto combined_done = [&] {
+            return done() || !duty_toggle;
+        };
+        while (!done()) {
+            while (!combined_done()) {
+                task(std::cref(combined_done)).get();
+                thread::maybe_yield();
+            }
+            cv.wait([&] {
+                return done() || duty_toggle;
+            }).get();
+        }
+        tmr_on.cancel();
+        tmr_off.cancel();
+    });
+}
+
+#include <fenv.h>
+
+template <typename T>
+auto var_fn(T& var) {
+    return [&var] { return var; };
+}
+
+int main(int ac, char** av) {
+    app_template app;
+    return app.run(ac, av, [] {
+        return seastar::async([] {
+            auto sg100 = seastar::create_scheduling_group("sg100", 100).get0();
+            auto ksg100 = seastar::defer([&] () noexcept { seastar::destroy_scheduling_group(sg100).get(); });
+            auto sg20 = seastar::create_scheduling_group("sg20", 20).get0();
+            auto ksg20 = seastar::defer([&] () noexcept { seastar::destroy_scheduling_group(sg20).get(); });
+            auto sg50 = seastar::create_scheduling_group("sg50", 50).get0();
+            auto ksg50 = seastar::defer([&] () noexcept { seastar::destroy_scheduling_group(sg50).get(); });
+
+            bool done = false;
+            auto end = timer<>([&done] {
+                done = true;
+            });
+
+            end.arm(10s);
+            unsigned ctr100 = 0, ctr20 = 0, ctr50 = 0;
+            fmt::print("running three scheduling groups with 100% duty cycle each:\n");
+            when_all(
+                    run_compute_intensive_tasks(sg100, var_fn(done), 5, ctr100, heavy_task),
+                    run_compute_intensive_tasks(sg20, var_fn(done), 3, ctr20, light_task),
+                    run_compute_intensive_tasks_in_threads(sg50, var_fn(done), 2, ctr50, medium_task)
+                    ).get();
+            fmt::print("{:10} {:15} {:10} {:12} {:8}\n", "shares", "task_time (us)", "executed", "runtime (ms)", "vruntime");
+            fmt::print("{:10d} {:15d} {:10d} {:12d} {:8.2f}\n", 100, 1000, ctr100, ctr100 * 1000 / 1000, ctr100 * 1000 / 1000 / 100.);
+            fmt::print("{:10d} {:15d} {:10d} {:12d} {:8.2f}\n", 20, 100, ctr20, ctr20 * 100 / 1000, ctr20 * 100 / 1000 / 20.);
+            fmt::print("{:10d} {:15d} {:10d} {:12d} {:8.2f}\n", 50, 400, ctr50, ctr50 * 400 / 1000, ctr50 * 400 / 1000 / 50.);
+            fmt::print("\n");
+
+            fmt::print("running two scheduling groups with 100%/50% duty cycles (period=1s:\n");
+            unsigned ctr100_2 = 0, ctr50_2 = 0;
+            done = false;
+            end.arm(10s);
+            when_all(
+                    run_compute_intensive_tasks(sg50, var_fn(done), 5, ctr50_2, heavy_task),
+                    run_with_duty_cycle(0.5, 1s, var_fn(done), [=, &ctr100_2] (done_func done) {
+                        return run_compute_intensive_tasks(sg100, done, 4, ctr100_2, heavy_task);
+                    })
+            ).get();
+            fmt::print("{:10} {:10} {:15} {:10} {:12} {:8}\n", "shares", "duty", "task_time (us)", "executed", "runtime (ms)", "vruntime");
+            fmt::print("{:10d} {:10d} {:15d} {:10d} {:12d} {:8.2f}\n", 100, 50, 1000, ctr100_2, ctr100_2 * 1000 / 1000, ctr100_2 * 1000 / 1000 / 100.);
+            fmt::print("{:10d} {:10d} {:15d} {:10d} {:12d} {:8.2f}\n", 50, 100, 400, ctr50_2, ctr50_2 * 1000 / 1000, ctr50_2 * 1000 / 1000 / 50.);
+
+            return 0;
+        });
+    });
+}
diff --git a/src/seastar/demos/sharded_parameter_demo.cc b/src/seastar/demos/sharded_parameter_demo.cc
new file mode 100644
index 000000000..09b53a9ab
--- /dev/null
+++ b/src/seastar/demos/sharded_parameter_demo.cc
@@ -0,0 +1,78 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright 2020 ScyllaDB
+ */
+
+
+// Demonstration of seastar::sharded_parameter
+
+#include <seastar/core/sharded.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/thread.hh>
+#include <seastar/util/closeable.hh>
+#include <cassert>
+
+// This is some service that we wish to run on all shards.
+class service_one {
+    int _capacity = 7;
+public:
+    // Pretend that this int is some important resource.
+    int get_capacity() const { return _capacity; }
+};
+
+// Another service that we run on all shards, that depends on service_one.
+class service_two {
+    int _resource_allocation;
+public:
+    service_two(service_one& s1, int resource_allocation) : _resource_allocation(resource_allocation) {}
+    int get_resource_allocation() const { return _resource_allocation; }
+};
+
+int main(int ac, char** av) {
+    seastar::app_template app;
+    return app.run(ac, av, [&] {
+        // sharded<> setup code is typically run in a seastar::thread
+        return seastar::async([&] {
+
+            // Launch service_one
+            seastar::sharded<service_one> s1;
+            s1.start().get();
+            auto stop_s1 = seastar::deferred_stop(s1);
+
+            auto calculate_half_capacity = [] (service_one& s1) {
+                return s1.get_capacity() / 2;
+            };
+
+            // Launch service_two, passing it per-shard dependencies from s1
+            seastar::sharded<service_two> s2;
+            // Start s2, passing two parameters to service_two's constructor
+            s2.start(
+                    // Each service_two instance will get a reference to a service_one instance on the same shard
+                    std::ref(s1),
+                    // This calculation will be performed on each shard
+                    seastar::sharded_parameter(calculate_half_capacity, std::ref(s1))
+            ).get();
+            auto stop_s2 = seastar::deferred_stop(s2);
+
+            s2.invoke_on_all([] (service_two& s2) {
+                assert(s2.get_resource_allocation() == 3);
+            }).get();
+        });
+    });
+}
diff --git a/src/seastar/demos/tcp_demo.cc b/src/seastar/demos/tcp_demo.cc
new file mode 100644
index 000000000..34ba69d7f
--- /dev/null
+++ b/src/seastar/demos/tcp_demo.cc
@@ -0,0 +1,75 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#include <seastar/net/ip.hh>
+#include <seastar/net/virtio.hh>
+#include <seastar/net/tcp.hh>
+#include <seastar/net/native-stack.hh>
+#include <seastar/core/reactor.hh>
+#include <fmt/printf.h>
+
+using namespace seastar;
+using namespace net;
+
+struct tcp_test {
+    ipv4& inet;
+    using tcp = net::tcp<ipv4_traits>;
+    tcp::listener _listener;
+    struct connection {
+        tcp::connection tcp_conn;
+        explicit connection(tcp::connection tc) : tcp_conn(std::move(tc)) {}
+        void run() {
+            // Read packets and echo back in the background.
+            (void)tcp_conn.wait_for_data().then([this] {
+                auto p = tcp_conn.read();
+                if (!p.len()) {
+                    tcp_conn.close_write();
+                    return;
+                }
+                fmt::print("read {:d} bytes\n", p.len());
+                (void)tcp_conn.send(std::move(p));
+                run();
+            });
+        }
+    };
+    tcp_test(ipv4& inet) : inet(inet), _listener(inet.get_tcp().listen(10000)) {}
+    void run() {
+        // Run all connections in the background.
+        (void)_listener.accept().then([this] (tcp::connection conn) {
+            (new connection(std::move(conn)))->run();
+            run();
+        });
+    }
+};
+
+int main(int ac, char** av) {
+    native_stack_options opts;
+
+    auto vnet = create_virtio_net_device(opts.virtio_opts, opts.lro);
+    interface netif(std::move(vnet));
+    ipv4 inet(&netif);
+    inet.set_host_address(ipv4_address("192.168.122.2"));
+    tcp_test tt(inet);
+    (void)engine().when_started().then([&tt] { tt.run(); });
+    engine().run();
+}
+
+
diff --git a/src/seastar/demos/tcp_sctp_client_demo.cc b/src/seastar/demos/tcp_sctp_client_demo.cc
new file mode 100644
index 000000000..3de72776e
--- /dev/null
+++ b/src/seastar/demos/tcp_sctp_client_demo.cc
@@ -0,0 +1,279 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#include <iostream>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/reactor.hh>
+#include <seastar/core/distributed.hh>
+#include <seastar/core/print.hh>
+#include <seastar/core/units.hh>
+
+using namespace seastar;
+using namespace net;
+using namespace std::chrono_literals;
+
+static int rx_msg_size = 4_KiB;
+static int tx_msg_total_size = 100_MiB;
+static int tx_msg_size = 4_KiB;
+static int tx_msg_nr = tx_msg_total_size / tx_msg_size;
+static std::string str_txbuf(tx_msg_size, 'X');
+
+class client;
+distributed<client> clients;
+
+transport protocol = transport::TCP;
+
+class client {
+private:
+    static constexpr unsigned _pings_per_connection = 10000;
+    unsigned _total_pings;
+    unsigned _concurrent_connections;
+    ipv4_addr _server_addr;
+    std::string _test;
+    lowres_clock::time_point _earliest_started = lowres_clock::time_point::max();
+    lowres_clock::time_point _latest_finished = lowres_clock::time_point::min();
+    size_t _processed_bytes;
+    unsigned _num_reported;
+public:
+    class connection {
+        connected_socket _fd;
+        input_stream<char> _read_buf;
+        output_stream<char> _write_buf;
+        size_t _bytes_read = 0;
+        size_t _bytes_write = 0;
+    public:
+        connection(connected_socket&& fd)
+            : _fd(std::move(fd))
+            , _read_buf(_fd.input())
+            , _write_buf(_fd.output()) {}
+
+        future<> do_read() {
+            return _read_buf.read_exactly(rx_msg_size).then([this] (temporary_buffer<char> buf) {
+                _bytes_read += buf.size();
+                if (buf.size() == 0) {
+                    return make_ready_future();
+                } else {
+                    return do_read();
+                }
+            });
+        }
+
+        future<> do_write(int end) {
+            if (end == 0) {
+                return make_ready_future();
+            }
+            return _write_buf.write(str_txbuf).then([this] {
+                _bytes_write += tx_msg_size;
+                return _write_buf.flush();
+            }).then([this, end] {
+                return do_write(end - 1);
+            });
+        }
+
+        future<> ping(int times) {
+            return _write_buf.write("ping").then([this] {
+                return _write_buf.flush();
+            }).then([this, times] {
+                return _read_buf.read_exactly(4).then([this, times] (temporary_buffer<char> buf) {
+                    if (buf.size() != 4) {
+                        fmt::print(std::cerr, "illegal packet received: {}\n", buf.size());
+                        return make_ready_future();
+                    }
+                    auto str = std::string(buf.get(), buf.size());
+                    if (str != "pong") {
+                        fmt::print(std::cerr, "illegal packet received: {}\n", buf.size());
+                        return make_ready_future();
+                    }
+                    if (times > 0) {
+                        return ping(times - 1);
+                    } else {
+                        return make_ready_future();
+                    }
+                });
+            });
+        }
+
+        future<size_t> rxrx() {
+            return _write_buf.write("rxrx").then([this] {
+                return _write_buf.flush();
+            }).then([this] {
+                return do_write(tx_msg_nr).then([this] {
+                    return _write_buf.close();
+                }).then([this] {
+                    return make_ready_future<size_t>(_bytes_write);
+                });
+            });
+        }
+
+        future<size_t> txtx() {
+            return _write_buf.write("txtx").then([this] {
+                return _write_buf.flush();
+            }).then([this] {
+                return do_read().then([this] {
+                    return make_ready_future<size_t>(_bytes_read);
+                });
+            });
+        }
+    };
+
+    future<> ping_test(connection *conn) {
+        auto started = lowres_clock::now();
+        return conn->ping(_pings_per_connection).then([started] {
+            auto finished = lowres_clock::now();
+            (void)clients.invoke_on(0, &client::ping_report, started, finished);
+        });
+    }
+
+    future<> rxrx_test(connection *conn) {
+        auto started = lowres_clock::now();
+        return conn->rxrx().then([started] (size_t bytes) {
+            auto finished = lowres_clock::now();
+            (void)clients.invoke_on(0, &client::rxtx_report, started, finished, bytes);
+        });
+    }
+
+    future<> txtx_test(connection *conn) {
+        auto started = lowres_clock::now();
+        return conn->txtx().then([started] (size_t bytes) {
+            auto finished = lowres_clock::now();
+            (void)clients.invoke_on(0, &client::rxtx_report, started, finished, bytes);
+        });
+    }
+
+    void ping_report(lowres_clock::time_point started, lowres_clock::time_point finished) {
+        if (_earliest_started > started)
+            _earliest_started = started;
+        if (_latest_finished < finished)
+            _latest_finished = finished;
+        if (++_num_reported == _concurrent_connections) {
+            auto elapsed = _latest_finished - _earliest_started;
+            auto usecs = std::chrono::duration_cast<std::chrono::microseconds>(elapsed).count();
+            auto secs = static_cast<double>(usecs) / static_cast<double>(1000 * 1000);
+            fmt::print(std::cout, "========== ping ============\n");
+            fmt::print(std::cout, "Server: {}\n", _server_addr);
+            fmt::print(std::cout,"Connections: {}\n", _concurrent_connections);
+            fmt::print(std::cout, "Total PingPong: {}\n", _total_pings);
+            fmt::print(std::cout, "Total Time(Secs): {}\n", secs);
+            fmt::print(std::cout, "Requests/Sec: {}\n",
+                static_cast<double>(_total_pings) / secs);
+            (void)clients.stop().then([] {
+                engine().exit(0);
+            });
+        }
+    }
+
+    void rxtx_report(lowres_clock::time_point started, lowres_clock::time_point finished, size_t bytes) {
+        if (_earliest_started > started)
+            _earliest_started = started;
+        if (_latest_finished < finished)
+            _latest_finished = finished;
+        _processed_bytes += bytes;
+        if (++_num_reported == _concurrent_connections) {
+            auto elapsed = _latest_finished - _earliest_started;
+            auto usecs = std::chrono::duration_cast<std::chrono::microseconds>(elapsed).count();
+            auto secs = static_cast<double>(usecs) / static_cast<double>(1000 * 1000);
+            fmt::print(std::cout, "========== {} ============\n", _test);
+            fmt::print(std::cout, "Server: {}\n", _server_addr);
+            fmt::print(std::cout, "Connections: {}\n", _concurrent_connections);
+            fmt::print(std::cout, "Bytes Received(MiB): {}\n", _processed_bytes / 1_MiB);
+            fmt::print(std::cout, "Total Time(Secs): {}\n", secs);
+            fmt::print(std::cout, "Bandwidth(Gbits/Sec): {}\n",
+                static_cast<double>((_processed_bytes * 8)) / (1000 * 1000 * 1000) / secs);
+            (void)clients.stop().then([] {
+                engine().exit(0);
+            });
+        }
+    }
+
+    future<> start(ipv4_addr server_addr, std::string test, unsigned ncon) {
+        _server_addr = server_addr;
+        _concurrent_connections = ncon * smp::count;
+        _total_pings = _pings_per_connection * _concurrent_connections;
+        _test = test;
+
+        for (unsigned i = 0; i < ncon; i++) {
+            socket_address local = socket_address(::sockaddr_in{AF_INET, INADDR_ANY, {0}});
+            (void)connect(make_ipv4_address(server_addr), local, protocol).then([this, test] (connected_socket fd) {
+                auto conn = new connection(std::move(fd));
+                (void)(this->*tests.at(test))(conn).then_wrapped([conn] (auto&& f) {
+                    delete conn;
+                    try {
+                        f.get();
+                    } catch (std::exception& ex) {
+                        fmt::print(std::cerr, "request error: {}\n", ex.what());
+                    }
+                });
+            });
+        }
+        return make_ready_future();
+    }
+    future<> stop() {
+        return make_ready_future();
+    }
+
+    typedef future<> (client::*test_fn)(connection *conn);
+    static const std::map<std::string, test_fn> tests;
+};
+
+namespace bpo = boost::program_options;
+
+int main(int ac, char ** av) {
+    app_template app;
+    app.add_options()
+        ("server", bpo::value<std::string>()->required(), "Server address")
+        ("test", bpo::value<std::string>()->default_value("ping"), "test type(ping | rxrx | txtx)")
+        ("conn", bpo::value<unsigned>()->default_value(16), "nr connections per cpu")
+        ("proto", bpo::value<std::string>()->default_value("tcp"), "transport protocol tcp|sctp")
+        ;
+
+    return app.run_deprecated(ac, av, [&app] {
+        auto&& config = app.configuration();
+        auto server = config["server"].as<std::string>();
+        auto test = config["test"].as<std::string>();
+        auto ncon = config["conn"].as<unsigned>();
+        auto proto = config["proto"].as<std::string>();
+
+        if (proto == "tcp") {
+            protocol = transport::TCP;
+        } else if (proto == "sctp") {
+            protocol = transport::SCTP;
+        } else {
+            fmt::print(std::cerr, "Error: --proto=tcp|sctp\n");
+            return engine().exit(1);
+        }
+
+        if (!client::tests.count(test)) {
+            fmt::print(std::cerr, "Error: -test=ping | rxrx | txtx\n");
+            return engine().exit(1);
+        }
+
+        (void)clients.start().then([server, test, ncon] () {
+            return clients.invoke_on_all(&client::start, ipv4_addr{server}, test, ncon);
+        });
+    });
+}
+
+const std::map<std::string, client::test_fn> client::tests = {
+        {"ping", &client::ping_test},
+        {"rxrx", &client::rxrx_test},
+        {"txtx", &client::txtx_test},
+};
+
diff --git a/src/seastar/demos/tcp_sctp_server_demo.cc b/src/seastar/demos/tcp_sctp_server_demo.cc
new file mode 100644
index 000000000..6918ab2ec
--- /dev/null
+++ b/src/seastar/demos/tcp_sctp_server_demo.cc
@@ -0,0 +1,205 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright 2014 Cloudius Systems
+ */
+
+#include <seastar/core/reactor.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/temporary_buffer.hh>
+#include <seastar/core/distributed.hh>
+#include <seastar/core/print.hh>
+#include <vector>
+#include <iostream>
+
+using namespace seastar;
+
+static std::string str_ping{"ping"};
+static std::string str_txtx{"txtx"};
+static std::string str_rxrx{"rxrx"};
+static std::string str_pong{"pong"};
+static std::string str_unknow{"unknow cmd"};
+static int tx_msg_total_size = 100 * 1024 * 1024;
+static int tx_msg_size = 4 * 1024;
+static int tx_msg_nr = tx_msg_total_size / tx_msg_size;
+static int rx_msg_size = 4 * 1024;
+static std::string str_txbuf(tx_msg_size, 'X');
+static bool enable_tcp = false;
+static bool enable_sctp = false;
+
+class tcp_server {
+    std::vector<server_socket> _tcp_listeners;
+    std::vector<server_socket> _sctp_listeners;
+public:
+    future<> listen(ipv4_addr addr) {
+        if (enable_tcp) {
+            listen_options lo;
+            lo.proto = transport::TCP;
+            lo.reuse_address = true;
+            _tcp_listeners.push_back(seastar::listen(make_ipv4_address(addr), lo));
+            do_accepts(_tcp_listeners);
+        }
+
+        if (enable_sctp) {
+            listen_options lo;
+            lo.proto = transport::SCTP;
+            lo.reuse_address = true;
+            _sctp_listeners.push_back(seastar::listen(make_ipv4_address(addr), lo));
+            do_accepts(_sctp_listeners);
+        }
+        return make_ready_future<>();
+    }
+
+    // FIXME: We should properly tear down the service here.
+    future<> stop() {
+        return make_ready_future<>();
+    }
+
+    void do_accepts(std::vector<server_socket>& listeners) {
+        int which = listeners.size() - 1;
+        // Accept in the background.
+        (void)listeners[which].accept().then([this, &listeners] (accept_result ar) mutable {
+            connected_socket fd = std::move(ar.connection);
+            socket_address addr = std::move(ar.remote_address);
+            auto conn = new connection(*this, std::move(fd), addr);
+            (void)conn->process().then_wrapped([conn] (auto&& f) {
+                delete conn;
+                try {
+                    f.get();
+                } catch (std::exception& ex) {
+                    std::cout << "request error " << ex.what() << "\n";
+                }
+            });
+            do_accepts(listeners);
+        }).then_wrapped([] (auto&& f) {
+            try {
+                f.get();
+            } catch (std::exception& ex) {
+                std::cout << "accept failed: " << ex.what() << "\n";
+            }
+        });
+    }
+    class connection {
+        connected_socket _fd;
+        input_stream<char> _read_buf;
+        output_stream<char> _write_buf;
+    public:
+        connection(tcp_server& server, connected_socket&& fd, socket_address addr)
+            : _fd(std::move(fd))
+            , _read_buf(_fd.input())
+            , _write_buf(_fd.output()) {}
+        future<> process() {
+             return read();
+        }
+        future<> read() {
+            if (_read_buf.eof()) {
+                return make_ready_future();
+            }
+            // Expect 4 bytes cmd from client
+            size_t n = 4;
+            return _read_buf.read_exactly(n).then([this] (temporary_buffer<char> buf) {
+                if (buf.size() == 0) {
+                    return make_ready_future();
+                }
+                auto cmd = std::string(buf.get(), buf.size());
+                // pingpong test
+                if (cmd == str_ping) {
+                    return _write_buf.write(str_pong).then([this] {
+                        return _write_buf.flush();
+                    }).then([this] {
+                        return this->read();
+                    });
+                // server tx test
+                } else if (cmd == str_txtx) {
+                    return tx_test();
+                // server tx test
+                } else if (cmd == str_rxrx) {
+                    return rx_test();
+                // unknow test
+                } else {
+                    return _write_buf.write(str_unknow).then([this] {
+                        return _write_buf.flush();
+                    }).then([] {
+                        return make_ready_future();
+                    });
+                }
+            });
+        }
+        future<> do_write(int end) {
+            if (end == 0) {
+                return make_ready_future<>();
+            }
+            return _write_buf.write(str_txbuf).then([this] {
+                return _write_buf.flush();
+            }).then([this, end] {
+                return do_write(end - 1);
+            });
+        }
+        future<> tx_test() {
+            return do_write(tx_msg_nr).then([this] {
+                return _write_buf.close();
+            }).then([] {
+                return make_ready_future<>();
+            });
+        }
+        future<> do_read() {
+            return _read_buf.read_exactly(rx_msg_size).then([this] (temporary_buffer<char> buf) {
+                if (buf.size() == 0) {
+                    return make_ready_future();
+                } else {
+                    return do_read();
+                }
+            });
+        }
+        future<> rx_test() {
+            return do_read().then([] {
+                return make_ready_future<>();
+            });
+        }
+    };
+};
+
+namespace bpo = boost::program_options;
+
+int main(int ac, char** av) {
+    app_template app;
+    app.add_options()
+        ("port", bpo::value<uint16_t>()->default_value(10000), "TCP server port")
+        ("tcp", bpo::value<std::string>()->default_value("yes"), "tcp listen")
+        ("sctp", bpo::value<std::string>()->default_value("no"), "sctp listen") ;
+    return app.run_deprecated(ac, av, [&] {
+        auto&& config = app.configuration();
+        uint16_t port = config["port"].as<uint16_t>();
+        enable_tcp = config["tcp"].as<std::string>() == "yes";
+        enable_sctp = config["sctp"].as<std::string>() == "yes";
+        if (!enable_tcp && !enable_sctp) {
+            fmt::print(std::cerr, "Error: no protocols enabled. Use \"--tcp yes\" and/or \"--sctp yes\" to enable\n");
+            return engine().exit(1);
+        }
+        auto server = new distributed<tcp_server>;
+        (void)server->start().then([server = std::move(server), port] () mutable {
+            engine().at_exit([server] {
+                return server->stop();
+            });
+            // Start listening in the background.
+            (void)server->invoke_on_all(&tcp_server::listen, ipv4_addr{port});
+        }).then([port] {
+            std::cout << "Seastar TCP server listening on port " << port << " ...\n";
+        });
+    });
+}
diff --git a/src/seastar/demos/tls_echo_server.hh b/src/seastar/demos/tls_echo_server.hh
new file mode 100644
index 000000000..e7185dac9
--- /dev/null
+++ b/src/seastar/demos/tls_echo_server.hh
@@ -0,0 +1,121 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright 2017 ScyllaDB
+ */
+#pragma once
+
+#include <seastar/core/sstring.hh>
+#include <seastar/core/do_with.hh>
+#include <seastar/core/sharded.hh>
+#include <seastar/core/gate.hh>
+#include <seastar/core/loop.hh>
+#include <seastar/net/tls.hh>
+#include <seastar/util/log.hh>
+#include <iostream>
+
+using namespace seastar;
+
+struct streams {
+    connected_socket s;
+    input_stream<char> in;
+    output_stream<char> out;
+
+    streams(connected_socket cs) : s(std::move(cs)), in(s.input()), out(s.output())
+    {}
+};
+
+class echoserver {
+    server_socket _socket;
+    shared_ptr<tls::server_credentials> _certs;
+    seastar::gate _gate;
+    bool _stopped = false;
+    bool _verbose = false;
+public:
+    echoserver(bool verbose = false)
+            : _certs(make_shared<tls::server_credentials>(make_shared<tls::dh_params>()))
+            , _verbose(verbose)
+    {}
+
+    future<> listen(socket_address addr, sstring crtfile, sstring keyfile, tls::client_auth ca = tls::client_auth::NONE) {
+        _certs->set_client_auth(ca);
+        return _certs->set_x509_key_file(crtfile, keyfile, tls::x509_crt_format::PEM).then([this, addr] {
+            ::listen_options opts;
+            opts.reuse_address = true;
+
+            _socket = tls::listen(_certs, addr, opts);
+
+            // Listen in background.
+            (void)repeat([this] {
+                if (_stopped) {
+                    return make_ready_future<stop_iteration>(stop_iteration::yes);
+                }
+                return with_gate(_gate, [this] {
+                    return _socket.accept().then([this](accept_result ar) {
+                        ::connected_socket s = std::move(ar.connection);
+                        socket_address a = std::move(ar.remote_address);
+                        if (_verbose) {
+                            std::cout << "Got connection from "<< a << std::endl;
+                        }
+                        auto strms = make_lw_shared<streams>(std::move(s));
+                        return repeat([strms, this]() {
+                            return strms->in.read().then([this, strms](temporary_buffer<char> buf) {
+                                if (buf.empty()) {
+                                    if (_verbose) {
+                                        std::cout << "EOM" << std::endl;
+                                    }
+                                    return make_ready_future<stop_iteration>(stop_iteration::yes);
+                                }
+                                sstring tmp(buf.begin(), buf.end());
+                                if (_verbose) {
+                                    std::cout << "Read " << tmp.size() << "B" << std::endl;
+                                }
+                                return strms->out.write(tmp).then([strms]() {
+                                    return strms->out.flush();
+                                }).then([] {
+                                    return make_ready_future<stop_iteration>(stop_iteration::no);
+                                });
+                            });
+                        }).then([strms]{
+                            return strms->out.close();
+                        }).handle_exception([](auto ep) {
+                        }).finally([this, strms]{
+                            if (_verbose) {
+                                std::cout << "Ending session" << std::endl;
+                            }
+                            return strms->in.close();
+                        });
+                    }).handle_exception([this](auto ep) {
+                        if (!_stopped) {
+                            std::cerr << "Error: " << ep << std::endl;
+                        }
+                    }).then([this] {
+                        return make_ready_future<stop_iteration>(_stopped ? stop_iteration::yes : stop_iteration::no);
+                    });
+                });
+            });
+            return make_ready_future();
+        });
+    }
+
+    future<> stop() {
+        _stopped = true;
+        _socket.abort_accept();
+        return _gate.close();
+    }
+};
diff --git a/src/seastar/demos/tls_echo_server_demo.cc b/src/seastar/demos/tls_echo_server_demo.cc
new file mode 100644
index 000000000..222412019
--- /dev/null
+++ b/src/seastar/demos/tls_echo_server_demo.cc
@@ -0,0 +1,67 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright 2015 Cloudius Systems
+ */
+#include <cmath>
+#include <seastar/core/reactor.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/sleep.hh>
+#include <seastar/net/dns.hh>
+#include "tls_echo_server.hh"
+
+using namespace seastar;
+namespace bpo = boost::program_options;
+
+
+int main(int ac, char** av) {
+    app_template app;
+    app.add_options()
+                    ("port", bpo::value<uint16_t>()->default_value(10000), "Server port")
+                    ("address", bpo::value<std::string>()->default_value("127.0.0.1"), "Server address")
+                    ("cert,c", bpo::value<std::string>()->required(), "Server certificate file")
+                    ("key,k", bpo::value<std::string>()->required(), "Certificate key")
+                    ("verbose,v", bpo::value<bool>()->default_value(false)->implicit_value(true), "Verbose")
+                    ;
+    return app.run_deprecated(ac, av, [&] {
+        auto&& config = app.configuration();
+        uint16_t port = config["port"].as<uint16_t>();
+        auto crt = config["cert"].as<std::string>();
+        auto key = config["key"].as<std::string>();
+        auto addr = config["address"].as<std::string>();
+        auto verbose = config["verbose"].as<bool>();
+
+        std::cout << "Starting..." << std::endl;
+        return net::dns::resolve_name(addr).then([=](net::inet_address a) {
+            ipv4_addr ia(a, port);
+
+            auto server = ::make_shared<seastar::sharded<echoserver>>();
+            return server->start(verbose).then([=]() {
+                return server->invoke_on_all(&echoserver::listen, socket_address(ia), sstring(crt), sstring(key), tls::client_auth::NONE);
+            }).handle_exception([=](auto e) {
+                std::cerr << "Error: " << e << std::endl;
+                engine().exit(1);
+            }).then([=] {
+                std::cout << "TLS echo server running at " << addr << ":" << port << std::endl;
+                engine().at_exit([server] {
+                    return server->stop().finally([server] {});
+                });
+            });
+        });
+    });
+}
diff --git a/src/seastar/demos/tls_simple_client_demo.cc b/src/seastar/demos/tls_simple_client_demo.cc
new file mode 100644
index 000000000..d53461b0e
--- /dev/null
+++ b/src/seastar/demos/tls_simple_client_demo.cc
@@ -0,0 +1,133 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright 2015 Cloudius Systems
+ */
+#include <cmath>
+
+#include <seastar/core/shared_ptr.hh>
+#include <seastar/core/reactor.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/sleep.hh>
+#include <seastar/core/loop.hh>
+#include <seastar/net/dns.hh>
+#include "tls_echo_server.hh"
+
+using namespace seastar;
+namespace bpo = boost::program_options;
+
+
+int main(int ac, char** av) {
+    app_template app;
+    app.add_options()
+                    ("port", bpo::value<uint16_t>()->default_value(10000), "Remote port")
+                    ("address", bpo::value<std::string>()->default_value("127.0.0.1"), "Remote address")
+                    ("trust,t", bpo::value<std::string>(), "Trust store")
+                    ("msg,m", bpo::value<std::string>(), "Message to send")
+                    ("bytes,b", bpo::value<size_t>()->default_value(512), "Use random bytes of length as message")
+                    ("iterations,i", bpo::value<size_t>()->default_value(1), "Repeat X times")
+                    ("read-response,r", bpo::value<bool>()->default_value(true)->implicit_value(true), "Read echoed message")
+                    ("verbose,v", bpo::value<bool>()->default_value(false)->implicit_value(true), "Verbose operation")
+                    ("check-name,c", bpo::value<bool>()->default_value(false)->implicit_value(true), "Check server name")
+                    ("server-name,s", bpo::value<std::string>(), "Expected server name")
+                    ;
+
+
+    return app.run_deprecated(ac, av, [&] {
+        auto&& config = app.configuration();
+        uint16_t port = config["port"].as<uint16_t>();
+        auto addr = config["address"].as<std::string>();
+        auto n = config["bytes"].as<size_t>();
+        auto i = config["iterations"].as<size_t>();
+        auto do_read = config["read-response"].as<bool>();
+        auto verbose = config["verbose"].as<bool>();
+        auto check = config["check-name"].as<bool>();
+
+        std::cout << "Starting..." << std::endl;
+
+        auto certs = ::make_shared<tls::certificate_credentials>();
+        auto f = make_ready_future();
+
+        if (config.count("trust")) {
+            f = certs->set_x509_trust_file(config["trust"].as<std::string>(), tls::x509_crt_format::PEM);
+        }
+
+        seastar::shared_ptr<sstring> msg;
+
+        if (config.count("msg")) {
+            msg = seastar::make_shared<sstring>(config["msg"].as<std::string>());
+        } else {
+            msg = seastar::make_shared<sstring>(uninitialized_string(n));
+            for (size_t i = 0; i < n; ++i) {
+                (*msg)[i] = '0' + char(::rand() % 30);
+            }
+        }
+
+        sstring server_name;
+        if (config.count("server-name")) {
+            server_name = config["server-name"].as<std::string>();
+        }
+        if (verbose) {
+            std::cout << "Msg (" << msg->size() << "B):" << std::endl << *msg << std::endl;
+        }
+        return f.then([=]() {
+            return net::dns::get_host_by_name(addr).then([=](net::hostent e) {
+                ipv4_addr ia(e.addr_list.front(), port);
+
+                sstring name;
+                if (check) {
+                    name = server_name.empty() ? e.names.front() : server_name;
+                }
+                return tls::connect(certs, ia, name).then([=](::connected_socket s) {
+                    auto strms = ::make_lw_shared<streams>(std::move(s));
+                    auto range = boost::irange(size_t(0), i);
+                    return do_for_each(range, [=](auto) {
+                        auto f = strms->out.write(*msg);
+                        if (!do_read) {
+                            return strms->out.close().then([f = std::move(f)]() mutable {
+                                return std::move(f);
+                            });
+                        }
+                        return f.then([=]() {
+                            return strms->out.flush().then([=] {
+                                return strms->in.read_exactly(msg->size()).then([=](temporary_buffer<char> buf) {
+                                    sstring tmp(buf.begin(), buf.end());
+                                    if (tmp != *msg) {
+                                        std::cerr << "Got garbled message!" << std::endl;
+                                        if (verbose) {
+                                            std::cout << "Got (" << tmp.size() << ") :" << std::endl << tmp << std::endl;
+                                        }
+                                        throw std::runtime_error("Got garbled message!");
+                                    }
+                                });
+                            });
+                        });
+                    }).then([strms, do_read]{
+                        return do_read ? strms->out.close() : make_ready_future<>();
+                    }).finally([strms]{
+                        return strms->in.close();
+                    });
+                });
+            }).handle_exception([](auto ep) {
+                std::cerr << "Error: " << ep << std::endl;
+            });
+        }).finally([] {
+            engine().exit(0);
+        });
+    });
+}
diff --git a/src/seastar/demos/tutorial_examples.cc b/src/seastar/demos/tutorial_examples.cc
new file mode 100644
index 000000000..0f67f5fd8
--- /dev/null
+++ b/src/seastar/demos/tutorial_examples.cc
@@ -0,0 +1,117 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2020 ScyllaDB.
+ */
+
+#include <iostream>
+
+#include <seastar/core/seastar.hh>
+#include <seastar/core/reactor.hh>
+#include <seastar/core/future-util.hh>
+#include <seastar/net/api.hh>
+
+seastar::future<> service_loop() {
+    return seastar::do_with(seastar::listen(seastar::make_ipv4_address({1234})),
+            [] (auto& listener) {
+        return seastar::keep_doing([&listener] () {
+            return listener.accept().then(
+                [] (seastar::accept_result res) {
+                    std::cout << "Accepted connection from " << res.remote_address << "\n";
+            });
+        });
+    });
+}
+
+const char* canned_response = "Seastar is the future!\n";
+
+seastar::future<> service_loop_2() {
+    seastar::listen_options lo;
+    lo.reuse_address = true;
+    return seastar::do_with(seastar::listen(seastar::make_ipv4_address({1234}), lo),
+            [] (auto& listener) {
+        return seastar::keep_doing([&listener] () {
+            return listener.accept().then(
+                    [] (seastar::accept_result res) {
+                auto s = std::move(res.connection);
+                auto out = s.output();
+                return seastar::do_with(std::move(s), std::move(out),
+                        [] (auto& s, auto& out) {
+                    return out.write(canned_response).then([&out] {
+                        return out.close();
+                    });
+                });
+            });
+        });
+    });
+}
+
+seastar::future<> handle_connection_3(seastar::connected_socket s,
+                                    seastar::socket_address a) {
+    auto out = s.output();
+    auto in = s.input();
+    return do_with(std::move(s), std::move(out), std::move(in),
+            [] (auto& s, auto& out, auto& in) {
+        return seastar::repeat([&out, &in] {
+            return in.read().then([&out] (auto buf) {
+                if (buf) {
+                    return out.write(std::move(buf)).then([&out] {
+                        return out.flush();
+                    }).then([] {
+                        return seastar::stop_iteration::no;
+                    });
+                } else {
+                    return seastar::make_ready_future<seastar::stop_iteration>(
+                            seastar::stop_iteration::yes);
+                }
+            });
+        }).then([&out] {
+            return out.close();
+        });
+    });
+}
+
+seastar::future<> service_loop_3() {
+    seastar::listen_options lo;
+    lo.reuse_address = true;
+    return seastar::do_with(seastar::listen(seastar::make_ipv4_address({1234}), lo),
+            [] (auto& listener) {
+        return seastar::keep_doing([&listener] () {
+            return listener.accept().then(
+                    [] (seastar::accept_result res) {
+                // Note we ignore, not return, the future returned by
+                // handle_connection(), so we do not wait for one
+                // connection to be handled before accepting the next one.
+                (void)handle_connection_3(std::move(res.connection), std::move(res.remote_address)).handle_exception(
+                        [] (std::exception_ptr ep) {
+                    fmt::print(stderr, "Could not handle connection: {}\n", ep);
+                });
+            });
+        });
+    });
+}
+
+#include <seastar/core/app-template.hh>
+
+int main(int ac, char** av) {
+    seastar::app_template app;
+    return app.run(ac, av, [] {
+        std::cout << "This is the tutorial examples demo.  It is not running anything but rather makes sure the tutorial examples compile" << std::endl;
+        return seastar::make_ready_future<>();
+    });
+}
diff --git a/src/seastar/demos/udp_client_demo.cc b/src/seastar/demos/udp_client_demo.cc
new file mode 100644
index 000000000..016b03c21
--- /dev/null
+++ b/src/seastar/demos/udp_client_demo.cc
@@ -0,0 +1,89 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#include <seastar/core/app-template.hh>
+#include <seastar/core/seastar.hh>
+#include <seastar/core/timer.hh>
+#include <seastar/net/api.hh>
+#include <iostream>
+
+using namespace seastar;
+using namespace net;
+using namespace std::chrono_literals;
+
+class client {
+private:
+    udp_channel _chan;
+    uint64_t n_sent {};
+    uint64_t n_received {};
+    uint64_t n_failed {};
+    timer<> _stats_timer;
+public:
+    void start(ipv4_addr server_addr) {
+        std::cout << "Sending to " << server_addr << std::endl;
+
+        _chan = make_udp_channel();
+
+        _stats_timer.set_callback([this] {
+            std::cout << "Out: " << n_sent << " pps, \t";
+            std::cout << "Err: " << n_failed << " pps, \t";
+            std::cout << "In: " << n_received << " pps" << std::endl;
+            n_sent = 0;
+            n_received = 0;
+            n_failed = 0;
+        });
+        _stats_timer.arm_periodic(1s);
+
+        // Run sender in background.
+        (void)keep_doing([this, server_addr] {
+            return _chan.send(server_addr, "hello!\n")
+                .then_wrapped([this] (auto&& f) {
+                    try {
+                        f.get();
+                        n_sent++;
+                    } catch (...) {
+                        n_failed++;
+                    }
+                });
+        });
+
+        // Run receiver in background.
+        (void)keep_doing([this] {
+            return _chan.receive().then([this] (auto) {
+                n_received++;
+            });
+        });
+    }
+};
+
+namespace bpo = boost::program_options;
+
+int main(int ac, char ** av) {
+    client _client;
+    app_template app;
+    app.add_options()
+        ("server", bpo::value<std::string>(), "Server address")
+        ;
+    return app.run_deprecated(ac, av, [&_client, &app] {
+        auto&& config = app.configuration();
+        _client.start(config["server"].as<std::string>());
+    });
+}
diff --git a/src/seastar/demos/udp_server_demo.cc b/src/seastar/demos/udp_server_demo.cc
new file mode 100644
index 000000000..ec25cce5d
--- /dev/null
+++ b/src/seastar/demos/udp_server_demo.cc
@@ -0,0 +1,82 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#include <iostream>
+#include <seastar/core/reactor.hh>
+#include <seastar/core/distributed.hh>
+#include <seastar/core/app-template.hh>
+
+using namespace seastar;
+using namespace net;
+using namespace std::chrono_literals;
+
+class udp_server {
+private:
+    udp_channel _chan;
+    timer<> _stats_timer;
+    uint64_t _n_sent {};
+public:
+    void start(uint16_t port) {
+        ipv4_addr listen_addr{port};
+        _chan = make_udp_channel(listen_addr);
+
+        _stats_timer.set_callback([this] {
+            std::cout << "Out: " << _n_sent << " pps" << std::endl;
+            _n_sent = 0;
+        });
+        _stats_timer.arm_periodic(1s);
+
+        // Run server in background.
+        (void)keep_doing([this] {
+            return _chan.receive().then([this] (udp_datagram dgram) {
+                return _chan.send(dgram.get_src(), std::move(dgram.get_data())).then([this] {
+                    _n_sent++;
+                });
+            });
+        });
+    }
+    // FIXME: we should properly tear down the service here.
+    future<> stop() {
+        return make_ready_future<>();
+    }
+};
+
+namespace bpo = boost::program_options;
+
+int main(int ac, char ** av) {
+    app_template app;
+    app.add_options()
+        ("port", bpo::value<uint16_t>()->default_value(10000), "UDP server port") ;
+    return app.run_deprecated(ac, av, [&] {
+        auto&& config = app.configuration();
+        uint16_t port = config["port"].as<uint16_t>();
+        auto server = new distributed<udp_server>;
+        // Run server in background.
+        (void)server->start().then([server = std::move(server), port] () mutable {
+            engine().at_exit([server] {
+                return server->stop();
+            });
+            return server->invoke_on_all(&udp_server::start, port);
+        }).then([port] {
+            std::cout << "Seastar UDP server listening on port " << port << " ...\n";
+        });
+    });
+}
diff --git a/src/seastar/demos/udp_zero_copy_demo.cc b/src/seastar/demos/udp_zero_copy_demo.cc
new file mode 100644
index 000000000..a0d7733a3
--- /dev/null
+++ b/src/seastar/demos/udp_zero_copy_demo.cc
@@ -0,0 +1,153 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#include <seastar/core/seastar.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/scattered_message.hh>
+#include <seastar/core/vector-data-sink.hh>
+#include <seastar/core/shared_ptr.hh>
+#include <seastar/core/units.hh>
+#include <seastar/core/timer.hh>
+#include <seastar/net/api.hh>
+#include <random>
+#include <iomanip>
+#include <iostream>
+
+using namespace seastar;
+using namespace net;
+using namespace std::chrono_literals;
+namespace bpo = boost::program_options;
+
+template <typename Duration>
+typename Duration::rep to_seconds(Duration d) {
+    return std::chrono::duration_cast<std::chrono::seconds>(d).count();
+}
+
+class server {
+private:
+    udp_channel _chan;
+    timer<> _stats_timer;
+    uint64_t _n_sent {};
+    size_t _chunk_size;
+    bool _copy;
+    std::vector<packet> _packets;
+    std::unique_ptr<output_stream<char>> _out;
+    steady_clock_type::time_point _last;
+    sstring _key;
+    size_t _packet_size = 8*KB;
+    char* _mem;
+    size_t _mem_size;
+    std::mt19937 _rnd;
+    std::random_device _randem_dev;
+    std::uniform_int_distribution<size_t> _chunk_distribution;
+private:
+    char* next_chunk() {
+        return _mem + _chunk_distribution(_rnd);
+    }
+public:
+    server()
+        : _rnd(std::random_device()()) {
+    }
+    future<> send(ipv4_addr dst, packet p) {
+        return _chan.send(dst, std::move(p)).then([this] {
+            _n_sent++;
+        });
+    }
+    void start(int chunk_size, bool copy, size_t mem_size) {
+        ipv4_addr listen_addr{10000};
+        _chan = make_udp_channel(listen_addr);
+
+        std::cout << "Listening on " << listen_addr << std::endl;
+
+        _last = steady_clock_type::now();
+        _stats_timer.set_callback([this] {
+            auto now = steady_clock_type::now();
+            std::cout << "Out: "
+                << std::setprecision(2) << std::fixed
+                << (double)_n_sent / to_seconds(now - _last)
+                << " pps" << std::endl;
+            _last = now;
+            _n_sent = 0;
+        });
+        _stats_timer.arm_periodic(1s);
+
+        _chunk_size = chunk_size;
+        _copy = copy;
+        _key = sstring(new char[64], 64);
+
+        _out = std::make_unique<output_stream<char>>(
+            data_sink(std::make_unique<vector_data_sink>(_packets)), _packet_size);
+
+        _mem = new char[mem_size];
+        _mem_size = mem_size;
+
+        _chunk_distribution = std::uniform_int_distribution<size_t>(0, _mem_size - _chunk_size * 3);
+
+        assert(3 * _chunk_size <= _packet_size);
+
+        // Run sender in background.
+        (void)keep_doing([this] {
+            return _chan.receive().then([this] (udp_datagram dgram) {
+                auto chunk = next_chunk();
+                lw_shared_ptr<sstring> item;
+                if (_copy) {
+                    _packets.clear();
+                    // FIXME: future is discarded
+                    (void)_out->write(chunk, _chunk_size);
+                    chunk += _chunk_size;
+                    (void)_out->write(chunk, _chunk_size);
+                    chunk += _chunk_size;
+                    (void)_out->write(chunk, _chunk_size);
+                    (void)_out->flush();
+                    assert(_packets.size() == 1);
+                    return send(dgram.get_src(), std::move(_packets[0]));
+                } else {
+                    auto chunk = next_chunk();
+                    scattered_message<char> msg;
+                    msg.reserve(3);
+                    msg.append_static(chunk, _chunk_size);
+                    msg.append_static(chunk, _chunk_size);
+                    msg.append_static(chunk, _chunk_size);
+                    return send(dgram.get_src(), std::move(msg).release());
+                }
+            });
+        });
+    }
+};
+
+int main(int ac, char ** av) {
+    server s;
+    app_template app;
+    app.add_options()
+        ("chunk-size", bpo::value<int>()->default_value(1024),
+             "Chunk size")
+        ("mem-size", bpo::value<int>()->default_value(512),
+             "Memory pool size in MiB")
+        ("copy", "Copy data rather than send via zero-copy")
+        ;
+    return app.run_deprecated(ac, av, [&app, &s] {
+        auto&& config = app.configuration();
+        auto chunk_size = config["chunk-size"].as<int>();
+        auto mem_size = (size_t)config["mem-size"].as<int>() * MB;
+        auto copy = config.count("copy");
+        s.start(chunk_size, copy, mem_size);
+    });
+}
diff --git a/src/seastar/demos/websocket_demo.cc b/src/seastar/demos/websocket_demo.cc
new file mode 100644
index 000000000..c19cb0fc2
--- /dev/null
+++ b/src/seastar/demos/websocket_demo.cc
@@ -0,0 +1,66 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2021 ScyllaDB Ltd.
+ */
+
+#include <iostream>
+#include <seastar/websocket/server.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/fstream.hh>
+#include <seastar/core/sleep.hh>
+#include <seastar/core/seastar.hh>
+#include <seastar/core/loop.hh>
+#include <seastar/core/thread.hh>
+#include <seastar/util/defer.hh>
+
+using namespace seastar;
+using namespace seastar::experimental;
+
+int main(int argc, char** argv) {
+    seastar::app_template app;
+    app.run(argc, argv, [] () -> seastar::future<> {
+        return async([] {
+            static websocket::server ws;
+            ws.register_handler("echo", [] (input_stream<char>& in,
+                        output_stream<char>& out) {
+                return repeat([&in, &out]() {
+                    return in.read().then([&out](temporary_buffer<char> f) {
+                        std::cerr << "f.size(): " << f.size() << "\n";
+                        if (f.empty()) {
+                            return make_ready_future<stop_iteration>(stop_iteration::yes);
+                        } else {
+                            return out.write(std::move(f)).then([&out]() {
+                                return out.flush().then([] {
+                                    return make_ready_future<stop_iteration>(stop_iteration::no);
+                                });
+                            });
+                        }
+                    });
+                });
+            });
+            auto d = defer([] () noexcept {
+                ws.stop().get();
+            });
+            ws.listen(socket_address(ipv4_addr("127.0.0.1", 8123)));
+            std::cout << "Listening on 127.0.0.1:8123 for 1 hour (interruptible, hit Ctrl-C to stop)..." << std::endl;
+            seastar::sleep_abortable(std::chrono::hours(1)).get();
+            std::cout << "Stopping the server, deepest thanks to all clients, hope we meet again" << std::endl;
+        });
+    });
+}