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/*
* 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();
});
});
});
}
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