Adding upstream version 14.2.21.upstream/14.2.21upstream

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

8 files changed, 2800 insertions, 0 deletions

diff --git a/src/seastar/apps/memcached/CMakeLists.txt b/src/seastar/apps/memcached/CMakeLists.txt
new file mode 100644
index 00000000..ec213fd0
--- /dev/null
+++ b/src/seastar/apps/memcached/CMakeLists.txt
@@ -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) 2018 Scylladb, Ltd.
+#
+
+set (Seastar_APP_MEMCACHED_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
+set (Seastar_APP_MEMCACHED_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
+
+seastar_generate_ragel (
+  TARGET app_memcached_ascii
+  VAR app_memcached_ascii_file
+  IN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/ascii.rl
+  OUT_FILE ${CMAKE_CURRENT_BINARY_DIR}/ascii.hh)
+
+seastar_add_app (memcached
+  SOURCES
+    ${app_memcached_ascii_file}
+    memcache.cc
+    memcached.hh)
+
+target_include_directories (app_memcached
+  PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
+
+add_dependencies (app_memcached app_memcached_ascii)
+
+#
+# Tests.
+#
+
+if (Seastar_TESTING)
+  add_subdirectory (tests)
+endif ()
diff --git a/src/seastar/apps/memcached/ascii.rl b/src/seastar/apps/memcached/ascii.rl
new file mode 100644
index 00000000..04d161ff
--- /dev/null
+++ b/src/seastar/apps/memcached/ascii.rl
@@ -0,0 +1,154 @@
+/*
+ * 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/ragel.hh>
+#include "memcached.hh"
+#include <memory>
+#include <algorithm>
+#include <functional>
+
+using namespace seastar;
+
+%%{
+
+machine memcache_ascii_protocol;
+
+access _fsm_;
+
+action mark {
+    g.mark_start(p);
+}
+
+action start_blob {
+    g.mark_start(p);
+    _size_left = _size;
+}
+
+action advance_blob {
+    auto len = std::min((uint32_t)(pe - p), _size_left);
+    _size_left -= len;
+    p += len;
+    if (_size_left == 0) {
+        _blob = str();
+        p--;
+        fret;
+    }
+    p--;
+}
+
+crlf = '\r\n';
+sp = ' ';
+u32 = digit+ >{ _u32 = 0; } ${ _u32 *= 10; _u32 += fc - '0'; };
+u64 = digit+ >{ _u64 = 0; } ${ _u64 *= 10; _u64 += fc - '0'; };
+key = [^ ]+ >mark %{ _key = memcache::item_key(str()); };
+flags = digit+ >mark %{ _flags_str = str(); };
+expiration = u32 %{ _expiration = _u32; };
+size = u32 >mark %{ _size = _u32; _size_str = str(); };
+blob := any+ >start_blob $advance_blob;
+maybe_noreply = (sp "noreply" @{ _noreply = true; })? >{ _noreply = false; };
+maybe_expiration = (sp expiration)? >{ _expiration = 0; };
+version_field = u64 %{ _version = _u64; };
+
+insertion_params = sp key sp flags sp expiration sp size maybe_noreply (crlf @{ fcall blob; } ) crlf;
+set = "set" insertion_params @{ _state = state::cmd_set; };
+add = "add" insertion_params @{ _state = state::cmd_add; };
+replace = "replace" insertion_params @{ _state = state::cmd_replace; };
+cas = "cas" sp key sp flags sp expiration sp size sp version_field maybe_noreply (crlf @{ fcall blob; } ) crlf @{ _state = state::cmd_cas; };
+get = "get" (sp key %{ _keys.emplace_back(std::move(_key)); })+ crlf @{ _state = state::cmd_get; };
+gets = "gets" (sp key %{ _keys.emplace_back(std::move(_key)); })+ crlf @{ _state = state::cmd_gets; };
+delete = "delete" sp key maybe_noreply crlf @{ _state = state::cmd_delete; };
+flush = "flush_all" maybe_expiration maybe_noreply crlf @{ _state = state::cmd_flush_all; };
+version = "version" crlf @{ _state = state::cmd_version; };
+stats = "stats" crlf @{ _state = state::cmd_stats; };
+stats_hash = "stats hash" crlf @{ _state = state::cmd_stats_hash; };
+incr = "incr" sp key sp u64 maybe_noreply crlf @{ _state = state::cmd_incr; };
+decr = "decr" sp key sp u64 maybe_noreply crlf @{ _state = state::cmd_decr; };
+main := (add | replace | set | get | gets | delete | flush | version | cas | stats | incr | decr
+    | stats_hash) >eof{ _state = state::eof; };
+
+prepush {
+    prepush();
+}
+
+postpop {
+    postpop();
+}
+
+}%%
+
+class memcache_ascii_parser : public ragel_parser_base<memcache_ascii_parser> {
+    %% write data nofinal noprefix;
+public:
+    enum class state {
+        error,
+        eof,
+        cmd_set,
+        cmd_cas,
+        cmd_add,
+        cmd_replace,
+        cmd_get,
+        cmd_gets,
+        cmd_delete,
+        cmd_flush_all,
+        cmd_version,
+        cmd_stats,
+        cmd_stats_hash,
+        cmd_incr,
+        cmd_decr,
+    };
+    state _state;
+    uint32_t _u32;
+    uint64_t _u64;
+    memcache::item_key _key;
+    sstring _flags_str;
+    uint32_t _expiration;
+    uint32_t _size;
+    sstring _size_str;
+    uint32_t _size_left;
+    uint64_t _version;
+    sstring _blob;
+    bool _noreply;
+    std::vector<memcache::item_key> _keys;
+public:
+    void init() {
+        init_base();
+        _state = state::error;
+        _keys.clear();
+        %% write init;
+    }
+
+    char* parse(char* p, char* pe, char* eof) {
+        sstring_builder::guard g(_builder, p, pe);
+        auto str = [this, &g, &p] { g.mark_end(p); return get_str(); };
+        %% write exec;
+        if (_state != state::error) {
+            return p;
+        }
+        if (p != pe) {
+            p = pe;
+            return p;
+        }
+        return nullptr;
+    }
+    bool eof() const {
+        return _state == state::eof;
+    }
+};
diff --git a/src/seastar/apps/memcached/memcache.cc b/src/seastar/apps/memcached/memcache.cc
new file mode 100644
index 00000000..4cce0e92
--- /dev/null
+++ b/src/seastar/apps/memcached/memcache.cc
@@ -0,0 +1,1464 @@
+/*
+ * 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 2014-2015 Cloudius Systems
+ */
+
+#include <boost/intrusive/unordered_set.hpp>
+#include <boost/intrusive/list.hpp>
+#include <boost/intrusive_ptr.hpp>
+#include <boost/lexical_cast.hpp>
+#include <boost/optional.hpp>
+#include <iostream>
+#include <iomanip>
+#include <sstream>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/future-util.hh>
+#include <seastar/core/timer-set.hh>
+#include <seastar/core/shared_ptr.hh>
+#include <seastar/core/stream.hh>
+#include <seastar/core/memory.hh>
+#include <seastar/core/units.hh>
+#include <seastar/core/distributed.hh>
+#include <seastar/core/vector-data-sink.hh>
+#include <seastar/core/bitops.hh>
+#include <seastar/core/slab.hh>
+#include <seastar/core/align.hh>
+#include <seastar/net/api.hh>
+#include <seastar/net/packet-data-source.hh>
+#include "ascii.hh"
+#include "memcached.hh"
+#include <unistd.h>
+
+#define PLATFORM "seastar"
+#define VERSION "v1.0"
+#define VERSION_STRING PLATFORM " " VERSION
+
+using namespace seastar;
+using namespace net;
+
+namespace memcache {
+
+namespace bi = boost::intrusive;
+
+static constexpr double default_slab_growth_factor = 1.25;
+static constexpr uint64_t default_slab_page_size = 1UL*MB;
+static constexpr uint64_t default_per_cpu_slab_size = 0UL; // zero means reclaimer is enabled.
+static __thread slab_allocator<item>* slab;
+static thread_local std::unique_ptr<slab_allocator<item>> slab_holder;
+
+template<typename T>
+using optional = boost::optional<T>;
+
+using clock_type = lowres_clock;
+
+//
+// "Expiration" is a uint32_t value.
+// The minimal value of _time is when "expiration" is set to (seconds_in_a_month
+// + 1).
+// In this case _time will have a value of
+//
+// (seconds_in_a_month + 1 - Wall_Clock_Time_Since_Epoch)
+//
+// because lowres_clock now() initialized to zero when the application starts.
+//
+// We will use a timepoint at LLONG_MIN to represent a "never expire" value
+// since it will not collide with the minimum _time value mentioned above for
+// about 290 thousand years to come.
+//
+static constexpr clock_type::time_point never_expire_timepoint = clock_type::time_point(clock_type::duration::min());
+
+struct expiration {
+    using time_point = clock_type::time_point;
+    using duration   = time_point::duration;
+
+    static constexpr uint32_t seconds_in_a_month = 60U * 60 * 24 * 30;
+    time_point _time = never_expire_timepoint;
+
+    expiration() {}
+
+    expiration(clock_type::duration wc_to_clock_type_delta, uint32_t s) {
+        using namespace std::chrono;
+
+        static_assert(sizeof(clock_type::duration::rep) >= 8, "clock_type::duration::rep must be at least 8 bytes wide");
+
+        if (s == 0U) {
+            return; // means never expire.
+        } else if (s <= seconds_in_a_month) {
+            _time = clock_type::now() + seconds(s); // from delta
+        } else {
+            //
+            // seastar::reactor supports only a monotonic clock at the moment
+            // therefore this may make the elements with the absolute expiration
+            // time expire at the wrong time if the wall clock has been updated
+            // during the expiration period. However the original memcached has
+            // the same weakness.
+            //
+            // TODO: Fix this when a support for system_clock-based timers is
+            // added to the seastar::reactor.
+            //
+            _time = time_point(seconds(s) + wc_to_clock_type_delta); // from real time
+        }
+    }
+
+    bool ever_expires() {
+        return _time != never_expire_timepoint;
+    }
+
+    time_point to_time_point() {
+        return _time;
+    }
+};
+
+class item : public slab_item_base {
+public:
+    using version_type = uint64_t;
+    using time_point = expiration::time_point;
+    using duration = expiration::duration;
+    static constexpr uint8_t field_alignment = alignof(void*);
+private:
+    using hook_type = bi::unordered_set_member_hook<>;
+    // TODO: align shared data to cache line boundary
+    version_type _version;
+    hook_type _cache_link;
+    bi::list_member_hook<> _timer_link;
+    size_t _key_hash;
+    expiration _expiry;
+    uint32_t _value_size;
+    uint32_t _slab_page_index;
+    uint16_t _ref_count;
+    uint8_t _key_size;
+    uint8_t _ascii_prefix_size;
+    char _data[]; // layout: data=key, (data+key_size)=ascii_prefix, (data+key_size+ascii_prefix_size)=value.
+    friend class cache;
+public:
+    item(uint32_t slab_page_index, item_key&& key, sstring&& ascii_prefix,
+         sstring&& value, expiration expiry, version_type version = 1)
+        : _version(version)
+        , _key_hash(key.hash())
+        , _expiry(expiry)
+        , _value_size(value.size())
+        , _slab_page_index(slab_page_index)
+        , _ref_count(0U)
+        , _key_size(key.key().size())
+        , _ascii_prefix_size(ascii_prefix.size())
+    {
+        assert(_key_size <= std::numeric_limits<uint8_t>::max());
+        assert(_ascii_prefix_size <= std::numeric_limits<uint8_t>::max());
+        // storing key
+        memcpy(_data, key.key().c_str(), _key_size);
+        // storing ascii_prefix
+        memcpy(_data + align_up(_key_size, field_alignment), ascii_prefix.c_str(), _ascii_prefix_size);
+        // storing value
+        memcpy(_data + align_up(_key_size, field_alignment) + align_up(_ascii_prefix_size, field_alignment),
+               value.c_str(), _value_size);
+    }
+
+    item(const item&) = delete;
+    item(item&&) = delete;
+
+    clock_type::time_point get_timeout() {
+        return _expiry.to_time_point();
+    }
+
+    version_type version() {
+        return _version;
+    }
+
+    const compat::string_view key() const {
+        return compat::string_view(_data, _key_size);
+    }
+
+    const compat::string_view ascii_prefix() const {
+        const char *p = _data + align_up(_key_size, field_alignment);
+        return compat::string_view(p, _ascii_prefix_size);
+    }
+
+    const compat::string_view value() const {
+        const char *p = _data + align_up(_key_size, field_alignment) +
+            align_up(_ascii_prefix_size, field_alignment);
+        return compat::string_view(p, _value_size);
+    }
+
+    size_t key_size() const {
+        return _key_size;
+    }
+
+    size_t ascii_prefix_size() const {
+        return _ascii_prefix_size;
+    }
+
+    size_t value_size() const {
+        return _value_size;
+    }
+
+    optional<uint64_t> data_as_integral() {
+        auto str = value().data();
+        if (str[0] == '-') {
+            return {};
+        }
+
+        auto len = _value_size;
+
+        // Strip trailing space
+        while (len && str[len - 1] == ' ') {
+            len--;
+        }
+
+        try {
+            return {boost::lexical_cast<uint64_t>(str, len)};
+        } catch (const boost::bad_lexical_cast& e) {
+            return {};
+        }
+    }
+
+    // needed by timer_set
+    bool cancel() {
+        return false;
+    }
+
+    // Methods required by slab allocator.
+    uint32_t get_slab_page_index() const {
+        return _slab_page_index;
+    }
+    bool is_unlocked() const {
+        return _ref_count == 1;
+    }
+
+    friend bool operator==(const item &a, const item &b) {
+         return (a._key_hash == b._key_hash) &&
+            (a._key_size == b._key_size) &&
+            (memcmp(a._data, b._data, a._key_size) == 0);
+    }
+
+    friend std::size_t hash_value(const item &i) {
+        return i._key_hash;
+    }
+
+    friend inline void intrusive_ptr_add_ref(item* it) {
+        assert(it->_ref_count >= 0);
+        ++it->_ref_count;
+        if (it->_ref_count == 2) {
+            slab->lock_item(it);
+        }
+    }
+
+    friend inline void intrusive_ptr_release(item* it) {
+        --it->_ref_count;
+        if (it->_ref_count == 1) {
+            slab->unlock_item(it);
+        } else if (it->_ref_count == 0) {
+            slab->free(it);
+        }
+        assert(it->_ref_count >= 0);
+    }
+
+    friend class item_key_cmp;
+};
+
+struct item_key_cmp
+{
+private:
+    bool compare(const item_key& key, const item& it) const {
+        return (it._key_hash == key.hash()) &&
+            (it._key_size == key.key().size()) &&
+            (memcmp(it._data, key.key().c_str(), it._key_size) == 0);
+    }
+public:
+    bool operator()(const item_key& key, const item& it) const {
+        return compare(key, it);
+    }
+
+    bool operator()(const item& it, const item_key& key) const {
+        return compare(key, it);
+    }
+};
+
+using item_ptr = foreign_ptr<boost::intrusive_ptr<item>>;
+
+struct cache_stats {
+    size_t _get_hits {};
+    size_t _get_misses {};
+    size_t _set_adds {};
+    size_t _set_replaces {};
+    size_t _cas_hits {};
+    size_t _cas_misses {};
+    size_t _cas_badval {};
+    size_t _delete_misses {};
+    size_t _delete_hits {};
+    size_t _incr_misses {};
+    size_t _incr_hits {};
+    size_t _decr_misses {};
+    size_t _decr_hits {};
+    size_t _expired {};
+    size_t _evicted {};
+    size_t _bytes {};
+    size_t _resize_failure {};
+    size_t _size {};
+    size_t _reclaims{};
+
+    void operator+=(const cache_stats& o) {
+        _get_hits += o._get_hits;
+        _get_misses += o._get_misses;
+        _set_adds += o._set_adds;
+        _set_replaces += o._set_replaces;
+        _cas_hits += o._cas_hits;
+        _cas_misses += o._cas_misses;
+        _cas_badval += o._cas_badval;
+        _delete_misses += o._delete_misses;
+        _delete_hits += o._delete_hits;
+        _incr_misses += o._incr_misses;
+        _incr_hits += o._incr_hits;
+        _decr_misses += o._decr_misses;
+        _decr_hits += o._decr_hits;
+        _expired += o._expired;
+        _evicted += o._evicted;
+        _bytes += o._bytes;
+        _resize_failure += o._resize_failure;
+        _size += o._size;
+        _reclaims += o._reclaims;
+    }
+};
+
+enum class cas_result {
+    not_found, stored, bad_version
+};
+
+struct remote_origin_tag {
+    template <typename T>
+    static inline
+    T move_if_local(T& ref) {
+        return ref;
+    }
+};
+
+struct local_origin_tag {
+    template <typename T>
+    static inline
+    T move_if_local(T& ref) {
+        return std::move(ref);
+    }
+};
+
+struct item_insertion_data {
+    item_key key;
+    sstring ascii_prefix;
+    sstring data;
+    expiration expiry;
+};
+
+class cache {
+private:
+    using cache_type = bi::unordered_set<item,
+        bi::member_hook<item, item::hook_type, &item::_cache_link>,
+        bi::power_2_buckets<true>,
+        bi::constant_time_size<true>>;
+    using cache_iterator = typename cache_type::iterator;
+    static constexpr size_t initial_bucket_count = 1 << 10;
+    static constexpr float load_factor = 0.75f;
+    size_t _resize_up_threshold = load_factor * initial_bucket_count;
+    std::vector<cache_type::bucket_type> _buckets;
+    cache_type _cache;
+    seastar::timer_set<item, &item::_timer_link> _alive;
+    timer<clock_type> _timer;
+    // delta in seconds between the current values of a wall clock and a clock_type clock
+    clock_type::duration _wc_to_clock_type_delta;
+    cache_stats _stats;
+    timer<clock_type> _flush_timer;
+private:
+    size_t item_size(item& item_ref) {
+        constexpr size_t field_alignment = alignof(void*);
+        return sizeof(item) +
+            align_up(item_ref.key_size(), field_alignment) +
+            align_up(item_ref.ascii_prefix_size(), field_alignment) +
+            item_ref.value_size();
+    }
+
+    size_t item_size(item_insertion_data& insertion) {
+        constexpr size_t field_alignment = alignof(void*);
+        auto size = sizeof(item) +
+            align_up(insertion.key.key().size(), field_alignment) +
+            align_up(insertion.ascii_prefix.size(), field_alignment) +
+            insertion.data.size();
+#ifdef __DEBUG__
+        static bool print_item_footprint = true;
+        if (print_item_footprint) {
+            print_item_footprint = false;
+            std::cout << __FUNCTION__ << ": " << size << "\n";
+            std::cout << "sizeof(item)      " << sizeof(item) << "\n";
+            std::cout << "key.size          " << insertion.key.key().size() << "\n";
+            std::cout << "value.size        " << insertion.data.size() << "\n";
+            std::cout << "ascii_prefix.size " << insertion.ascii_prefix.size() << "\n";
+        }
+#endif
+        return size;
+    }
+
+    template <bool IsInCache = true, bool IsInTimerList = true, bool Release = true>
+    void erase(item& item_ref) {
+        if (IsInCache) {
+            _cache.erase(_cache.iterator_to(item_ref));
+        }
+        if (IsInTimerList) {
+            if (item_ref._expiry.ever_expires()) {
+                _alive.remove(item_ref);
+            }
+        }
+        _stats._bytes -= item_size(item_ref);
+        if (Release) {
+            // memory used by item shouldn't be freed when slab is replacing it with another item.
+            intrusive_ptr_release(&item_ref);
+        }
+    }
+
+    void expire() {
+        using namespace std::chrono;
+
+        //
+        // Adjust the delta on every timer event to minimize an error caused
+        // by a wall clock adjustment.
+        //
+        _wc_to_clock_type_delta =
+            duration_cast<clock_type::duration>(clock_type::now().time_since_epoch() - system_clock::now().time_since_epoch());
+
+        auto exp = _alive.expire(clock_type::now());
+        while (!exp.empty()) {
+            auto item = &*exp.begin();
+            exp.pop_front();
+            erase<true, false>(*item);
+            _stats._expired++;
+        }
+        _timer.arm(_alive.get_next_timeout());
+    }
+
+    inline
+    cache_iterator find(const item_key& key) {
+        return _cache.find(key, std::hash<item_key>(), item_key_cmp());
+    }
+
+    template <typename Origin>
+    inline
+    cache_iterator add_overriding(cache_iterator i, item_insertion_data& insertion) {
+        auto& old_item = *i;
+        uint64_t old_item_version = old_item._version;
+
+        erase(old_item);
+
+        size_t size = item_size(insertion);
+        auto new_item = slab->create(size, Origin::move_if_local(insertion.key), Origin::move_if_local(insertion.ascii_prefix),
+            Origin::move_if_local(insertion.data), insertion.expiry, old_item_version + 1);
+        intrusive_ptr_add_ref(new_item);
+
+        auto insert_result = _cache.insert(*new_item);
+        assert(insert_result.second);
+        if (insertion.expiry.ever_expires() && _alive.insert(*new_item)) {
+            _timer.rearm(new_item->get_timeout());
+        }
+        _stats._bytes += size;
+        return insert_result.first;
+    }
+
+    template <typename Origin>
+    inline
+    void add_new(item_insertion_data& insertion) {
+        size_t size = item_size(insertion);
+        auto new_item = slab->create(size, Origin::move_if_local(insertion.key), Origin::move_if_local(insertion.ascii_prefix),
+            Origin::move_if_local(insertion.data), insertion.expiry);
+        intrusive_ptr_add_ref(new_item);
+        auto& item_ref = *new_item;
+        _cache.insert(item_ref);
+        if (insertion.expiry.ever_expires() && _alive.insert(item_ref)) {
+            _timer.rearm(item_ref.get_timeout());
+        }
+        _stats._bytes += size;
+        maybe_rehash();
+    }
+
+    void maybe_rehash() {
+        if (_cache.size() >= _resize_up_threshold) {
+            auto new_size = _cache.bucket_count() * 2;
+            std::vector<cache_type::bucket_type> old_buckets;
+            try {
+                old_buckets = std::exchange(_buckets, std::vector<cache_type::bucket_type>(new_size));
+            } catch (const std::bad_alloc& e) {
+                _stats._resize_failure++;
+                return;
+            }
+            _cache.rehash(typename cache_type::bucket_traits(_buckets.data(), new_size));
+            _resize_up_threshold = _cache.bucket_count() * load_factor;
+        }
+    }
+public:
+    cache(uint64_t per_cpu_slab_size, uint64_t slab_page_size)
+        : _buckets(initial_bucket_count)
+        , _cache(cache_type::bucket_traits(_buckets.data(), initial_bucket_count))
+    {
+        using namespace std::chrono;
+
+        _wc_to_clock_type_delta =
+            duration_cast<clock_type::duration>(clock_type::now().time_since_epoch() - system_clock::now().time_since_epoch());
+
+        _timer.set_callback([this] { expire(); });
+        _flush_timer.set_callback([this] { flush_all(); });
+
+        // initialize per-thread slab allocator.
+        slab_holder = std::make_unique<slab_allocator<item>>(default_slab_growth_factor, per_cpu_slab_size, slab_page_size,
+                [this](item& item_ref) { erase<true, true, false>(item_ref); _stats._evicted++; });
+        slab = slab_holder.get();
+#ifdef __DEBUG__
+        static bool print_slab_classes = true;
+        if (print_slab_classes) {
+            print_slab_classes = false;
+            slab->print_slab_classes();
+        }
+#endif
+    }
+
+    ~cache() {
+       flush_all();
+    }
+
+    void flush_all() {
+        _flush_timer.cancel();
+        _cache.erase_and_dispose(_cache.begin(), _cache.end(), [this] (item* it) {
+            erase<false, true>(*it);
+        });
+    }
+
+    void flush_at(uint32_t time) {
+        auto expiry = expiration(get_wc_to_clock_type_delta(), time);
+        _flush_timer.rearm(expiry.to_time_point());
+    }
+
+    template <typename Origin = local_origin_tag>
+    bool set(item_insertion_data& insertion) {
+        auto i = find(insertion.key);
+        if (i != _cache.end()) {
+            add_overriding<Origin>(i, insertion);
+            _stats._set_replaces++;
+            return true;
+        } else {
+            add_new<Origin>(insertion);
+            _stats._set_adds++;
+            return false;
+        }
+    }
+
+    template <typename Origin = local_origin_tag>
+    bool add(item_insertion_data& insertion) {
+        auto i = find(insertion.key);
+        if (i != _cache.end()) {
+            return false;
+        }
+
+        _stats._set_adds++;
+        add_new<Origin>(insertion);
+        return true;
+    }
+
+    template <typename Origin = local_origin_tag>
+    bool replace(item_insertion_data& insertion) {
+        auto i = find(insertion.key);
+        if (i == _cache.end()) {
+            return false;
+        }
+
+        _stats._set_replaces++;
+        add_overriding<Origin>(i, insertion);
+        return true;
+    }
+
+    bool remove(const item_key& key) {
+        auto i = find(key);
+        if (i == _cache.end()) {
+            _stats._delete_misses++;
+            return false;
+        }
+        _stats._delete_hits++;
+        auto& item_ref = *i;
+        erase(item_ref);
+        return true;
+    }
+
+    item_ptr get(const item_key& key) {
+        auto i = find(key);
+        if (i == _cache.end()) {
+            _stats._get_misses++;
+            return nullptr;
+        }
+        _stats._get_hits++;
+        auto& item_ref = *i;
+        return item_ptr(&item_ref);
+    }
+
+    template <typename Origin = local_origin_tag>
+    cas_result cas(item_insertion_data& insertion, item::version_type version) {
+        auto i = find(insertion.key);
+        if (i == _cache.end()) {
+            _stats._cas_misses++;
+            return cas_result::not_found;
+        }
+        auto& item_ref = *i;
+        if (item_ref._version != version) {
+            _stats._cas_badval++;
+            return cas_result::bad_version;
+        }
+        _stats._cas_hits++;
+        add_overriding<Origin>(i, insertion);
+        return cas_result::stored;
+    }
+
+    size_t size() {
+        return _cache.size();
+    }
+
+    size_t bucket_count() {
+        return _cache.bucket_count();
+    }
+
+    cache_stats stats() {
+        _stats._size = size();
+        return _stats;
+    }
+
+    template <typename Origin = local_origin_tag>
+    std::pair<item_ptr, bool> incr(item_key& key, uint64_t delta) {
+        auto i = find(key);
+        if (i == _cache.end()) {
+            _stats._incr_misses++;
+            return {item_ptr{}, false};
+        }
+        auto& item_ref = *i;
+        _stats._incr_hits++;
+        auto value = item_ref.data_as_integral();
+        if (!value) {
+            return {boost::intrusive_ptr<item>(&item_ref), false};
+        }
+        item_insertion_data insertion {
+            .key = Origin::move_if_local(key),
+            .ascii_prefix = sstring(item_ref.ascii_prefix().data(), item_ref.ascii_prefix_size()),
+            .data = to_sstring(*value + delta),
+            .expiry = item_ref._expiry
+        };
+        i = add_overriding<local_origin_tag>(i, insertion);
+        return {boost::intrusive_ptr<item>(&*i), true};
+    }
+
+    template <typename Origin = local_origin_tag>
+    std::pair<item_ptr, bool> decr(item_key& key, uint64_t delta) {
+        auto i = find(key);
+        if (i == _cache.end()) {
+            _stats._decr_misses++;
+            return {item_ptr{}, false};
+        }
+        auto& item_ref = *i;
+        _stats._decr_hits++;
+        auto value = item_ref.data_as_integral();
+        if (!value) {
+            return {boost::intrusive_ptr<item>(&item_ref), false};
+        }
+        item_insertion_data insertion {
+            .key = Origin::move_if_local(key),
+            .ascii_prefix = sstring(item_ref.ascii_prefix().data(), item_ref.ascii_prefix_size()),
+            .data = to_sstring(*value - std::min(*value, delta)),
+            .expiry = item_ref._expiry
+        };
+        i = add_overriding<local_origin_tag>(i, insertion);
+        return {boost::intrusive_ptr<item>(&*i), true};
+    }
+
+    std::pair<unsigned, foreign_ptr<lw_shared_ptr<std::string>>> print_hash_stats() {
+        static constexpr unsigned bits = sizeof(size_t) * 8;
+        size_t histo[bits + 1] {};
+        size_t max_size = 0;
+        unsigned max_bucket = 0;
+
+        for (size_t i = 0; i < _cache.bucket_count(); i++) {
+            size_t size = _cache.bucket_size(i);
+            unsigned bucket;
+            if (size == 0) {
+                bucket = 0;
+            } else {
+                bucket = bits - count_leading_zeros(size);
+            }
+            max_bucket = std::max(max_bucket, bucket);
+            max_size = std::max(max_size, size);
+            histo[bucket]++;
+        }
+
+        std::stringstream ss;
+
+        ss << "size: " << _cache.size() << "\n";
+        ss << "buckets: " << _cache.bucket_count() << "\n";
+        ss << "load: " << format("{:.2f}", (double)_cache.size() / _cache.bucket_count()) << "\n";
+        ss << "max bucket occupancy: " << max_size << "\n";
+        ss << "bucket occupancy histogram:\n";
+
+        for (unsigned i = 0; i < (max_bucket + 2); i++) {
+            ss << "  ";
+            if (i == 0) {
+                ss << "0: ";
+            } else if (i == 1) {
+                ss << "1: ";
+            } else {
+                ss << (1 << (i - 1)) << "+: ";
+            }
+            ss << histo[i] << "\n";
+        }
+        return {engine().cpu_id(), make_foreign(make_lw_shared<std::string>(ss.str()))};
+    }
+
+    future<> stop() { return make_ready_future<>(); }
+    clock_type::duration get_wc_to_clock_type_delta() { return _wc_to_clock_type_delta; }
+};
+
+class sharded_cache {
+private:
+    distributed<cache>& _peers;
+
+    inline
+    unsigned get_cpu(const item_key& key) {
+        return std::hash<item_key>()(key) % smp::count;
+    }
+public:
+    sharded_cache(distributed<cache>& peers) : _peers(peers) {}
+
+    future<> flush_all() {
+        return _peers.invoke_on_all(&cache::flush_all);
+    }
+
+    future<> flush_at(uint32_t time) {
+        return _peers.invoke_on_all(&cache::flush_at, time);
+    }
+
+    auto get_wc_to_clock_type_delta() { return _peers.local().get_wc_to_clock_type_delta(); }
+
+    // The caller must keep @insertion live until the resulting future resolves.
+    future<bool> set(item_insertion_data& insertion) {
+        auto cpu = get_cpu(insertion.key);
+        if (engine().cpu_id() == cpu) {
+            return make_ready_future<bool>(_peers.local().set(insertion));
+        }
+        return _peers.invoke_on(cpu, &cache::set<remote_origin_tag>, std::ref(insertion));
+    }
+
+    // The caller must keep @insertion live until the resulting future resolves.
+    future<bool> add(item_insertion_data& insertion) {
+        auto cpu = get_cpu(insertion.key);
+        if (engine().cpu_id() == cpu) {
+            return make_ready_future<bool>(_peers.local().add(insertion));
+        }
+        return _peers.invoke_on(cpu, &cache::add<remote_origin_tag>, std::ref(insertion));
+    }
+
+    // The caller must keep @insertion live until the resulting future resolves.
+    future<bool> replace(item_insertion_data& insertion) {
+        auto cpu = get_cpu(insertion.key);
+        if (engine().cpu_id() == cpu) {
+            return make_ready_future<bool>(_peers.local().replace(insertion));
+        }
+        return _peers.invoke_on(cpu, &cache::replace<remote_origin_tag>, std::ref(insertion));
+    }
+
+    // The caller must keep @key live until the resulting future resolves.
+    future<bool> remove(const item_key& key) {
+        auto cpu = get_cpu(key);
+        return _peers.invoke_on(cpu, &cache::remove, std::ref(key));
+    }
+
+    // The caller must keep @key live until the resulting future resolves.
+    future<item_ptr> get(const item_key& key) {
+        auto cpu = get_cpu(key);
+        return _peers.invoke_on(cpu, &cache::get, std::ref(key));
+    }
+
+    // The caller must keep @insertion live until the resulting future resolves.
+    future<cas_result> cas(item_insertion_data& insertion, item::version_type version) {
+        auto cpu = get_cpu(insertion.key);
+        if (engine().cpu_id() == cpu) {
+            return make_ready_future<cas_result>(_peers.local().cas(insertion, version));
+        }
+        return _peers.invoke_on(cpu, &cache::cas<remote_origin_tag>, std::ref(insertion), std::move(version));
+    }
+
+    future<cache_stats> stats() {
+        return _peers.map_reduce(adder<cache_stats>(), &cache::stats);
+    }
+
+    // The caller must keep @key live until the resulting future resolves.
+    future<std::pair<item_ptr, bool>> incr(item_key& key, uint64_t delta) {
+        auto cpu = get_cpu(key);
+        if (engine().cpu_id() == cpu) {
+            return make_ready_future<std::pair<item_ptr, bool>>(
+                _peers.local().incr<local_origin_tag>(key, delta));
+        }
+        return _peers.invoke_on(cpu, &cache::incr<remote_origin_tag>, std::ref(key), std::move(delta));
+    }
+
+    // The caller must keep @key live until the resulting future resolves.
+    future<std::pair<item_ptr, bool>> decr(item_key& key, uint64_t delta) {
+        auto cpu = get_cpu(key);
+        if (engine().cpu_id() == cpu) {
+            return make_ready_future<std::pair<item_ptr, bool>>(
+                _peers.local().decr(key, delta));
+        }
+        return _peers.invoke_on(cpu, &cache::decr<remote_origin_tag>, std::ref(key), std::move(delta));
+    }
+
+    future<> print_hash_stats(output_stream<char>& out) {
+        return _peers.map_reduce([&out] (std::pair<unsigned, foreign_ptr<lw_shared_ptr<std::string>>> data) mutable {
+            return out.write("=== CPU " + std::to_string(data.first) + " ===\r\n")
+                .then([&out, str = std::move(data.second)] {
+                    return out.write(*str);
+                });
+            }, &cache::print_hash_stats);
+    }
+};
+
+struct system_stats {
+    uint32_t _curr_connections {};
+    uint32_t _total_connections {};
+    uint64_t _cmd_get {};
+    uint64_t _cmd_set {};
+    uint64_t _cmd_flush {};
+    clock_type::time_point _start_time;
+public:
+    system_stats() {
+        _start_time = clock_type::time_point::max();
+    }
+    system_stats(clock_type::time_point start_time)
+        : _start_time(start_time) {
+    }
+    system_stats self() {
+        return *this;
+    }
+    void operator+=(const system_stats& other) {
+        _curr_connections += other._curr_connections;
+        _total_connections += other._total_connections;
+        _cmd_get += other._cmd_get;
+        _cmd_set += other._cmd_set;
+        _cmd_flush += other._cmd_flush;
+        _start_time = std::min(_start_time, other._start_time);
+    }
+    future<> stop() { return make_ready_future<>(); }
+};
+
+class ascii_protocol {
+private:
+    using this_type = ascii_protocol;
+    sharded_cache& _cache;
+    distributed<system_stats>& _system_stats;
+    memcache_ascii_parser _parser;
+    item_key _item_key;
+    item_insertion_data _insertion;
+    std::vector<item_ptr> _items;
+private:
+    static constexpr const char *msg_crlf = "\r\n";
+    static constexpr const char *msg_error = "ERROR\r\n";
+    static constexpr const char *msg_stored = "STORED\r\n";
+    static constexpr const char *msg_not_stored = "NOT_STORED\r\n";
+    static constexpr const char *msg_end = "END\r\n";
+    static constexpr const char *msg_value = "VALUE ";
+    static constexpr const char *msg_deleted = "DELETED\r\n";
+    static constexpr const char *msg_not_found = "NOT_FOUND\r\n";
+    static constexpr const char *msg_ok = "OK\r\n";
+    static constexpr const char *msg_version = "VERSION " VERSION_STRING "\r\n";
+    static constexpr const char *msg_exists = "EXISTS\r\n";
+    static constexpr const char *msg_stat = "STAT ";
+    static constexpr const char *msg_out_of_memory = "SERVER_ERROR Out of memory allocating new item\r\n";
+    static constexpr const char *msg_error_non_numeric_value = "CLIENT_ERROR cannot increment or decrement non-numeric value\r\n";
+private:
+    template <bool WithVersion>
+    static void append_item(scattered_message<char>& msg, item_ptr item) {
+        if (!item) {
+            return;
+        }
+
+        msg.append_static("VALUE ");
+        msg.append_static(item->key());
+        msg.append_static(item->ascii_prefix());
+
+        if (WithVersion) {
+             msg.append_static(" ");
+             msg.append(to_sstring(item->version()));
+        }
+
+        msg.append_static(msg_crlf);
+        msg.append_static(item->value());
+        msg.append_static(msg_crlf);
+        msg.on_delete([item = std::move(item)] {});
+    }
+
+    template <bool WithVersion>
+    future<> handle_get(output_stream<char>& out) {
+        _system_stats.local()._cmd_get++;
+        if (_parser._keys.size() == 1) {
+            return _cache.get(_parser._keys[0]).then([&out] (auto item) -> future<> {
+                scattered_message<char> msg;
+                this_type::append_item<WithVersion>(msg, std::move(item));
+                msg.append_static(msg_end);
+                return out.write(std::move(msg));
+            });
+        } else {
+            _items.clear();
+            return parallel_for_each(_parser._keys.begin(), _parser._keys.end(), [this] (const auto& key) {
+                return _cache.get(key).then([this] (auto item) {
+                    _items.emplace_back(std::move(item));
+                });
+            }).then([this, &out] () {
+                scattered_message<char> msg;
+                for (auto& item : _items) {
+                    append_item<WithVersion>(msg, std::move(item));
+                }
+                msg.append_static(msg_end);
+                return out.write(std::move(msg));
+            });
+        }
+    }
+
+    template <typename Value>
+    static future<> print_stat(output_stream<char>& out, const char* key, Value value) {
+        return out.write(msg_stat)
+                .then([&out, key] { return out.write(key); })
+                .then([&out] { return out.write(" "); })
+                .then([&out, value] { return out.write(to_sstring(value)); })
+                .then([&out] { return out.write(msg_crlf); });
+    }
+
+    future<> print_stats(output_stream<char>& out) {
+        return _cache.stats().then([this, &out] (auto stats) {
+            return _system_stats.map_reduce(adder<system_stats>(), &system_stats::self)
+                .then([&out, all_cache_stats = std::move(stats)] (auto all_system_stats) -> future<> {
+                    auto now = clock_type::now();
+                    auto total_items = all_cache_stats._set_replaces + all_cache_stats._set_adds
+                        + all_cache_stats._cas_hits;
+                    return print_stat(out, "pid", getpid())
+                        .then([&out, uptime = now - all_system_stats._start_time] {
+                            return print_stat(out, "uptime",
+                                std::chrono::duration_cast<std::chrono::seconds>(uptime).count());
+                        }).then([now, &out] {
+                            return print_stat(out, "time",
+                                std::chrono::duration_cast<std::chrono::seconds>(now.time_since_epoch()).count());
+                        }).then([&out] {
+                            return print_stat(out, "version", VERSION_STRING);
+                        }).then([&out] {
+                            return print_stat(out, "pointer_size", sizeof(void*)*8);
+                        }).then([&out, v = all_system_stats._curr_connections] {
+                            return print_stat(out, "curr_connections", v);
+                        }).then([&out, v = all_system_stats._total_connections] {
+                            return print_stat(out, "total_connections", v);
+                        }).then([&out, v = all_system_stats._curr_connections] {
+                            return print_stat(out, "connection_structures", v);
+                        }).then([&out, v = all_system_stats._cmd_get] {
+                            return print_stat(out, "cmd_get", v);
+                        }).then([&out, v = all_system_stats._cmd_set] {
+                            return print_stat(out, "cmd_set", v);
+                        }).then([&out, v = all_system_stats._cmd_flush] {
+                            return print_stat(out, "cmd_flush", v);
+                        }).then([&out] {
+                            return print_stat(out, "cmd_touch", 0);
+                        }).then([&out, v = all_cache_stats._get_hits] {
+                            return print_stat(out, "get_hits", v);
+                        }).then([&out, v = all_cache_stats._get_misses] {
+                            return print_stat(out, "get_misses", v);
+                        }).then([&out, v = all_cache_stats._delete_misses] {
+                            return print_stat(out, "delete_misses", v);
+                        }).then([&out, v = all_cache_stats._delete_hits] {
+                            return print_stat(out, "delete_hits", v);
+                        }).then([&out, v = all_cache_stats._incr_misses] {
+                            return print_stat(out, "incr_misses", v);
+                        }).then([&out, v = all_cache_stats._incr_hits] {
+                            return print_stat(out, "incr_hits", v);
+                        }).then([&out, v = all_cache_stats._decr_misses] {
+                            return print_stat(out, "decr_misses", v);
+                        }).then([&out, v = all_cache_stats._decr_hits] {
+                            return print_stat(out, "decr_hits", v);
+                        }).then([&out, v = all_cache_stats._cas_misses] {
+                            return print_stat(out, "cas_misses", v);
+                        }).then([&out, v = all_cache_stats._cas_hits] {
+                            return print_stat(out, "cas_hits", v);
+                        }).then([&out, v = all_cache_stats._cas_badval] {
+                            return print_stat(out, "cas_badval", v);
+                        }).then([&out] {
+                            return print_stat(out, "touch_hits", 0);
+                        }).then([&out] {
+                            return print_stat(out, "touch_misses", 0);
+                        }).then([&out] {
+                            return print_stat(out, "auth_cmds", 0);
+                        }).then([&out] {
+                            return print_stat(out, "auth_errors", 0);
+                        }).then([&out] {
+                            return print_stat(out, "threads", smp::count);
+                        }).then([&out, v = all_cache_stats._size] {
+                            return print_stat(out, "curr_items", v);
+                        }).then([&out, v = total_items] {
+                            return print_stat(out, "total_items", v);
+                        }).then([&out, v = all_cache_stats._expired] {
+                            return print_stat(out, "seastar.expired", v);
+                        }).then([&out, v = all_cache_stats._resize_failure] {
+                            return print_stat(out, "seastar.resize_failure", v);
+                        }).then([&out, v = all_cache_stats._evicted] {
+                            return print_stat(out, "evictions", v);
+                        }).then([&out, v = all_cache_stats._bytes] {
+                            return print_stat(out, "bytes", v);
+                        }).then([&out] {
+                            return out.write(msg_end);
+                        });
+                });
+        });
+    }
+public:
+    ascii_protocol(sharded_cache& cache, distributed<system_stats>& system_stats)
+        : _cache(cache)
+        , _system_stats(system_stats)
+    {}
+
+    void prepare_insertion() {
+        _insertion = item_insertion_data{
+            .key = std::move(_parser._key),
+            .ascii_prefix = make_sstring(" ", _parser._flags_str, " ", _parser._size_str),
+            .data = std::move(_parser._blob),
+            .expiry = expiration(_cache.get_wc_to_clock_type_delta(), _parser._expiration)
+        };
+    }
+
+    future<> handle(input_stream<char>& in, output_stream<char>& out) {
+        _parser.init();
+        return in.consume(_parser).then([this, &out] () -> future<> {
+            switch (_parser._state) {
+                case memcache_ascii_parser::state::eof:
+                    return make_ready_future<>();
+
+                case memcache_ascii_parser::state::error:
+                    return out.write(msg_error);
+
+                case memcache_ascii_parser::state::cmd_set:
+                {
+                    _system_stats.local()._cmd_set++;
+                    prepare_insertion();
+                    auto f = _cache.set(_insertion);
+                    if (_parser._noreply) {
+                        return std::move(f).discard_result();
+                    }
+                    return std::move(f).then([&out] (...) {
+                        return out.write(msg_stored);
+                    });
+                }
+
+                case memcache_ascii_parser::state::cmd_cas:
+                {
+                    _system_stats.local()._cmd_set++;
+                    prepare_insertion();
+                    auto f = _cache.cas(_insertion, _parser._version);
+                    if (_parser._noreply) {
+                        return std::move(f).discard_result();
+                    }
+                    return std::move(f).then([&out] (auto result) {
+                        switch (result) {
+                            case cas_result::stored:
+                                return out.write(msg_stored);
+                            case cas_result::not_found:
+                                return out.write(msg_not_found);
+                            case cas_result::bad_version:
+                                return out.write(msg_exists);
+                            default:
+                                std::abort();
+                        }
+                    });
+                }
+
+                case memcache_ascii_parser::state::cmd_add:
+                {
+                    _system_stats.local()._cmd_set++;
+                    prepare_insertion();
+                    auto f = _cache.add(_insertion);
+                    if (_parser._noreply) {
+                        return std::move(f).discard_result();
+                    }
+                    return std::move(f).then([&out] (bool added) {
+                        return out.write(added ? msg_stored : msg_not_stored);
+                    });
+                }
+
+                case memcache_ascii_parser::state::cmd_replace:
+                {
+                    _system_stats.local()._cmd_set++;
+                    prepare_insertion();
+                    auto f = _cache.replace(_insertion);
+                    if (_parser._noreply) {
+                        return std::move(f).discard_result();
+                    }
+                    return std::move(f).then([&out] (auto replaced) {
+                        return out.write(replaced ? msg_stored : msg_not_stored);
+                    });
+                }
+
+                case memcache_ascii_parser::state::cmd_get:
+                    return handle_get<false>(out);
+
+                case memcache_ascii_parser::state::cmd_gets:
+                    return handle_get<true>(out);
+
+                case memcache_ascii_parser::state::cmd_delete:
+                {
+                    auto f = _cache.remove(_parser._key);
+                    if (_parser._noreply) {
+                        return std::move(f).discard_result();
+                    }
+                    return std::move(f).then([&out] (bool removed) {
+                        return out.write(removed ? msg_deleted : msg_not_found);
+                    });
+                }
+
+                case memcache_ascii_parser::state::cmd_flush_all:
+                {
+                    _system_stats.local()._cmd_flush++;
+                    if (_parser._expiration) {
+                        auto f = _cache.flush_at(_parser._expiration);
+                        if (_parser._noreply) {
+                            return f;
+                        }
+                        return std::move(f).then([&out] {
+                            return out.write(msg_ok);
+                        });
+                    } else {
+                        auto f = _cache.flush_all();
+                        if (_parser._noreply) {
+                            return f;
+                        }
+                        return std::move(f).then([&out] {
+                            return out.write(msg_ok);
+                        });
+                    }
+                }
+
+                case memcache_ascii_parser::state::cmd_version:
+                    return out.write(msg_version);
+
+                case memcache_ascii_parser::state::cmd_stats:
+                    return print_stats(out);
+
+                case memcache_ascii_parser::state::cmd_stats_hash:
+                    return _cache.print_hash_stats(out);
+
+                case memcache_ascii_parser::state::cmd_incr:
+                {
+                    auto f = _cache.incr(_parser._key, _parser._u64);
+                    if (_parser._noreply) {
+                        return std::move(f).discard_result();
+                    }
+                    return std::move(f).then([&out] (auto result) {
+                        auto item = std::move(result.first);
+                        if (!item) {
+                            return out.write(msg_not_found);
+                        }
+                        auto incremented = result.second;
+                        if (!incremented) {
+                            return out.write(msg_error_non_numeric_value);
+                        }
+                        return out.write(item->value().data(), item->value_size()).then([&out] {
+                            return out.write(msg_crlf);
+                        });
+                    });
+                }
+
+                case memcache_ascii_parser::state::cmd_decr:
+                {
+                    auto f = _cache.decr(_parser._key, _parser._u64);
+                    if (_parser._noreply) {
+                        return std::move(f).discard_result();
+                    }
+                    return std::move(f).then([&out] (auto result) {
+                        auto item = std::move(result.first);
+                        if (!item) {
+                            return out.write(msg_not_found);
+                        }
+                        auto decremented = result.second;
+                        if (!decremented) {
+                            return out.write(msg_error_non_numeric_value);
+                        }
+                        return out.write(item->value().data(), item->value_size()).then([&out] {
+                            return out.write(msg_crlf);
+                        });
+                    });
+                }
+            };
+            std::abort();
+        }).then_wrapped([this, &out] (auto&& f) -> future<> {
+            // FIXME: then_wrapped() being scheduled even though no exception was triggered has a
+            // performance cost of about 2.6%. Not using it means maintainability penalty.
+            try {
+                f.get();
+            } catch (std::bad_alloc& e) {
+                if (_parser._noreply) {
+                    return make_ready_future<>();
+                }
+                return out.write(msg_out_of_memory);
+            }
+            return make_ready_future<>();
+        });
+    };
+};
+
+class udp_server {
+public:
+    static const size_t default_max_datagram_size = 1400;
+private:
+    sharded_cache& _cache;
+    distributed<system_stats>& _system_stats;
+    udp_channel _chan;
+    uint16_t _port;
+    size_t _max_datagram_size = default_max_datagram_size;
+
+    struct header {
+        packed<uint16_t> _request_id;
+        packed<uint16_t> _sequence_number;
+        packed<uint16_t> _n;
+        packed<uint16_t> _reserved;
+
+        template<typename Adjuster>
+        auto adjust_endianness(Adjuster a) {
+            return a(_request_id, _sequence_number, _n);
+        }
+    } __attribute__((packed));
+
+    struct connection {
+        ipv4_addr _src;
+        uint16_t _request_id;
+        input_stream<char> _in;
+        output_stream<char> _out;
+        std::vector<packet> _out_bufs;
+        ascii_protocol _proto;
+
+        connection(ipv4_addr src, uint16_t request_id, input_stream<char>&& in, size_t out_size,
+                sharded_cache& c, distributed<system_stats>& system_stats)
+            : _src(src)
+            , _request_id(request_id)
+            , _in(std::move(in))
+            , _out(output_stream<char>(data_sink(std::make_unique<vector_data_sink>(_out_bufs)), out_size, true))
+            , _proto(c, system_stats)
+        {}
+
+        future<> respond(udp_channel& chan) {
+            int i = 0;
+            return do_for_each(_out_bufs.begin(), _out_bufs.end(), [this, i, &chan] (packet& p) mutable {
+                header* out_hdr = p.prepend_header<header>(0);
+                out_hdr->_request_id = _request_id;
+                out_hdr->_sequence_number = i++;
+                out_hdr->_n = _out_bufs.size();
+                *out_hdr = hton(*out_hdr);
+                return chan.send(_src, std::move(p));
+            });
+        }
+    };
+
+public:
+    udp_server(sharded_cache& c, distributed<system_stats>& system_stats, uint16_t port = 11211)
+         : _cache(c)
+         , _system_stats(system_stats)
+         , _port(port)
+    {}
+
+    void set_max_datagram_size(size_t max_datagram_size) {
+        _max_datagram_size = max_datagram_size;
+    }
+
+    void start() {
+        _chan = engine().net().make_udp_channel({_port});
+        keep_doing([this] {
+            return _chan.receive().then([this](udp_datagram dgram) {
+                packet& p = dgram.get_data();
+                if (p.len() < sizeof(header)) {
+                    // dropping invalid packet
+                    return make_ready_future<>();
+                }
+
+                header hdr = ntoh(*p.get_header<header>());
+                p.trim_front(sizeof(hdr));
+
+                auto request_id = hdr._request_id;
+                auto in = as_input_stream(std::move(p));
+                auto conn = make_lw_shared<connection>(dgram.get_src(), request_id, std::move(in),
+                    _max_datagram_size - sizeof(header), _cache, _system_stats);
+
+                if (hdr._n != 1 || hdr._sequence_number != 0) {
+                    return conn->_out.write("CLIENT_ERROR only single-datagram requests supported\r\n").then([this, conn] {
+                        return conn->_out.flush().then([this, conn] {
+                            return conn->respond(_chan).then([conn] {});
+                        });
+                    });
+                }
+
+                return conn->_proto.handle(conn->_in, conn->_out).then([this, conn]() mutable {
+                    return conn->_out.flush().then([this, conn] {
+                        return conn->respond(_chan).then([conn] {});
+                    });
+                });
+            });
+        }).or_terminate();
+    };
+
+    future<> stop() { return make_ready_future<>(); }
+};
+
+class tcp_server {
+private:
+    lw_shared_ptr<server_socket> _listener;
+    sharded_cache& _cache;
+    distributed<system_stats>& _system_stats;
+    uint16_t _port;
+    struct connection {
+        connected_socket _socket;
+        socket_address _addr;
+        input_stream<char> _in;
+        output_stream<char> _out;
+        ascii_protocol _proto;
+        distributed<system_stats>& _system_stats;
+        connection(connected_socket&& socket, socket_address addr, sharded_cache& c, distributed<system_stats>& system_stats)
+            : _socket(std::move(socket))
+            , _addr(addr)
+            , _in(_socket.input())
+            , _out(_socket.output())
+            , _proto(c, system_stats)
+            , _system_stats(system_stats)
+        {
+            _system_stats.local()._curr_connections++;
+            _system_stats.local()._total_connections++;
+        }
+        ~connection() {
+            _system_stats.local()._curr_connections--;
+        }
+    };
+public:
+    tcp_server(sharded_cache& cache, distributed<system_stats>& system_stats, uint16_t port = 11211)
+        : _cache(cache)
+        , _system_stats(system_stats)
+        , _port(port)
+    {}
+
+    void start() {
+        listen_options lo;
+        lo.reuse_address = true;
+        _listener = engine().listen(make_ipv4_address({_port}), lo);
+        keep_doing([this] {
+            return _listener->accept().then([this] (connected_socket fd, socket_address addr) mutable {
+                auto conn = make_lw_shared<connection>(std::move(fd), addr, _cache, _system_stats);
+                do_until([conn] { return conn->_in.eof(); }, [conn] {
+                    return conn->_proto.handle(conn->_in, conn->_out).then([conn] {
+                        return conn->_out.flush();
+                    });
+                }).finally([conn] {
+                    return conn->_out.close().finally([conn]{});
+                });
+            });
+        }).or_terminate();
+    }
+
+    future<> stop() { return make_ready_future<>(); }
+};
+
+class stats_printer {
+private:
+    timer<> _timer;
+    sharded_cache& _cache;
+public:
+    stats_printer(sharded_cache& cache)
+        : _cache(cache) {}
+
+    void start() {
+        _timer.set_callback([this] {
+            _cache.stats().then([] (auto stats) {
+                auto gets_total = stats._get_hits + stats._get_misses;
+                auto get_hit_rate = gets_total ? ((double)stats._get_hits * 100 / gets_total) : 0;
+                auto sets_total = stats._set_adds + stats._set_replaces;
+                auto set_replace_rate = sets_total ? ((double)stats._set_replaces * 100/ sets_total) : 0;
+                std::cout << "items: " << stats._size << " "
+                    << std::setprecision(2) << std::fixed
+                    << "get: " << stats._get_hits << "/" << gets_total << " (" << get_hit_rate << "%) "
+                    << "set: " << stats._set_replaces << "/" << sets_total << " (" <<  set_replace_rate << "%)";
+                std::cout << std::endl;
+            });
+        });
+        _timer.arm_periodic(std::chrono::seconds(1));
+    }
+
+    future<> stop() { return make_ready_future<>(); }
+};
+
+} /* namespace memcache */
+
+int main(int ac, char** av) {
+    distributed<memcache::cache> cache_peers;
+    memcache::sharded_cache cache(cache_peers);
+    distributed<memcache::system_stats> system_stats;
+    distributed<memcache::udp_server> udp_server;
+    distributed<memcache::tcp_server> tcp_server;
+    memcache::stats_printer stats(cache);
+
+    namespace bpo = boost::program_options;
+    app_template app;
+    app.add_options()
+        ("max-datagram-size", bpo::value<int>()->default_value(memcache::udp_server::default_max_datagram_size),
+             "Maximum size of UDP datagram")
+        ("max-slab-size", bpo::value<uint64_t>()->default_value(memcache::default_per_cpu_slab_size/MB),
+             "Maximum memory to be used for items (value in megabytes) (reclaimer is disabled if set)")
+        ("slab-page-size", bpo::value<uint64_t>()->default_value(memcache::default_slab_page_size/MB),
+             "Size of slab page (value in megabytes)")
+        ("stats",
+             "Print basic statistics periodically (every second)")
+        ("port", bpo::value<uint16_t>()->default_value(11211),
+             "Specify UDP and TCP ports for memcached server to listen on")
+        ;
+
+    return app.run_deprecated(ac, av, [&] {
+        engine().at_exit([&] { return tcp_server.stop(); });
+        engine().at_exit([&] { return udp_server.stop(); });
+        engine().at_exit([&] { return cache_peers.stop(); });
+        engine().at_exit([&] { return system_stats.stop(); });
+
+        auto&& config = app.configuration();
+        uint16_t port = config["port"].as<uint16_t>();
+        uint64_t per_cpu_slab_size = config["max-slab-size"].as<uint64_t>() * MB;
+        uint64_t slab_page_size = config["slab-page-size"].as<uint64_t>() * MB;
+        return cache_peers.start(std::move(per_cpu_slab_size), std::move(slab_page_size)).then([&system_stats] {
+            return system_stats.start(memcache::clock_type::now());
+        }).then([&] {
+            std::cout << PLATFORM << " memcached " << VERSION << "\n";
+            return make_ready_future<>();
+        }).then([&, port] {
+            return tcp_server.start(std::ref(cache), std::ref(system_stats), port);
+        }).then([&tcp_server] {
+            return tcp_server.invoke_on_all(&memcache::tcp_server::start);
+        }).then([&, port] {
+            if (engine().net().has_per_core_namespace()) {
+                return udp_server.start(std::ref(cache), std::ref(system_stats), port);
+            } else {
+                return udp_server.start_single(std::ref(cache), std::ref(system_stats), port);
+            }
+        }).then([&] {
+            return udp_server.invoke_on_all(&memcache::udp_server::set_max_datagram_size,
+                    (size_t)config["max-datagram-size"].as<int>());
+        }).then([&] {
+            return udp_server.invoke_on_all(&memcache::udp_server::start);
+        }).then([&stats, start_stats = config.count("stats")] {
+            if (start_stats) {
+                stats.start();
+            }
+        });
+    });
+}
diff --git a/src/seastar/apps/memcached/memcached.hh b/src/seastar/apps/memcached/memcached.hh
new file mode 100644
index 00000000..9a587578
--- /dev/null
+++ b/src/seastar/apps/memcached/memcached.hh
@@ -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.
+ */
+
+#pragma once
+
+#include <seastar/core/sstring.hh>
+
+namespace memcache {
+
+using namespace seastar;
+
+class item;
+class cache;
+
+class item_key {
+private:
+    sstring _key;
+    size_t _hash;
+public:
+    item_key() = default;
+    item_key(item_key&) = default;
+    item_key(sstring key)
+        : _key(key)
+        , _hash(std::hash<sstring>()(key))
+    {}
+    item_key(item_key&& other)
+        : _key(std::move(other._key))
+        , _hash(other._hash)
+    {
+        other._hash = 0;
+    }
+    size_t hash() const {
+        return _hash;
+    }
+    const sstring& key() const {
+        return _key;
+    }
+    bool operator==(const item_key& other) const {
+        return other._hash == _hash && other._key == _key;
+    }
+    void operator=(item_key&& other) {
+        _key = std::move(other._key);
+        _hash = other._hash;
+        other._hash = 0;
+    }
+};
+
+}
+
+namespace std {
+
+template <>
+struct hash<memcache::item_key> {
+    size_t operator()(const memcache::item_key& key) {
+        return key.hash();
+    }
+};
+
+} /* namespace std */
diff --git a/src/seastar/apps/memcached/tests/CMakeLists.txt b/src/seastar/apps/memcached/tests/CMakeLists.txt
new file mode 100644
index 00000000..9301cea7
--- /dev/null
+++ b/src/seastar/apps/memcached/tests/CMakeLists.txt
@@ -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) 2018 Scylladb, Ltd.
+#
+
+if (Seastar_EXECUTE_ONLY_FAST_TESTS)
+  set (memcached_test_args --fast)
+else ()
+  set (memcached_test_args "")
+endif ()
+
+add_custom_target (app_memcached_test_memcached_run
+  DEPENDS
+    ${memcached_app}
+    ${CMAKE_CURRENT_SOURCE_DIR}/test.py
+    ${CMAKE_CURRENT_SOURCE_DIR}/test_memcached.py
+  COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/test.py --memcached $<TARGET_FILE:app_memcached> ${memcached_test_args}
+  USES_TERMINAL)
+
+add_test (
+  NAME Seastar.app.memcached.memcached
+  COMMAND ${CMAKE_COMMAND} --build ${Seastar_BINARY_DIR} --target app_memcached_test_memcached_run)
+
+set_tests_properties (Seastar.app.memcached.memcached
+  PROPERTIES
+    TIMEOUT ${Seastar_TEST_TIMEOUT})
+
+add_executable (app_memcached_test_ascii
+  test_ascii_parser.cc)
+
+add_dependencies (app_memcached_test_ascii app_memcached)
+
+target_include_directories (app_memcached_test_ascii
+  PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}
+    ${Seastar_APP_MEMCACHED_BINARY_DIR}
+    ${Seastar_APP_MEMCACHED_SOURCE_DIR})
+
+target_compile_definitions (app_memcached_test_ascii
+  PRIVATE SEASTAR_TESTING_MAIN)
+
+target_link_libraries (app_memcached_test_ascii
+  PRIVATE
+    seastar_with_flags
+    seastar_testing)
+
+add_custom_target (app_memcached_test_ascii_run
+  DEPENDS app_memcached_test_ascii
+  COMMAND app_memcached_test_ascii -- -c 2
+  USES_TERMINAL)
+
+add_test (
+  NAME Seastar.app.memcached.ascii
+  COMMAND ${CMAKE_COMMAND} --build ${Seastar_BINARY_DIR} --target app_memcached_test_ascii_run)
+
+set_tests_properties (Seastar.app.memcached.ascii
+  PROPERTIES
+    TIMEOUT ${Seastar_TEST_TIMEOUT})
diff --git a/src/seastar/apps/memcached/tests/test.py b/src/seastar/apps/memcached/tests/test.py
new file mode 100755
index 00000000..c2f2b80c
--- /dev/null
+++ b/src/seastar/apps/memcached/tests/test.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+#
+# 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.
+#
+import time
+import sys
+import os
+import argparse
+import subprocess
+
+DIR_PATH = os.path.dirname(os.path.realpath(__file__))
+
+def run(args, cmd):
+    mc = subprocess.Popen([args.memcached, '--smp=2'])
+    print('Memcached started.')
+    try:
+        cmdline = [DIR_PATH + '/test_memcached.py'] + cmd
+        if args.fast:
+            cmdline.append('--fast')
+        print('Running: ' + ' '.join(cmdline))
+        subprocess.check_call(cmdline)
+    finally:
+        print('Killing memcached...')
+        mc.terminate();
+        mc.wait()
+        print('Memcached killed.')
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Seastar test runner")
+    parser.add_argument('--fast',  action="store_true", help="Run only fast tests")
+    parser.add_argument('--memcached', required=True, help='Path of the memcached executable')
+    args = parser.parse_args()
+
+    run(args, [])
+    run(args, ['-U'])
diff --git a/src/seastar/apps/memcached/tests/test_ascii_parser.cc b/src/seastar/apps/memcached/tests/test_ascii_parser.cc
new file mode 100644
index 00000000..596d193e
--- /dev/null
+++ b/src/seastar/apps/memcached/tests/test_ascii_parser.cc
@@ -0,0 +1,335 @@
+/*
+ * 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 <limits>
+#include <seastar/testing/test_case.hh>
+#include <seastar/core/shared_ptr.hh>
+#include <seastar/net/packet-data-source.hh>
+#include "ascii.hh"
+#include <seastar/core/future-util.hh>
+
+using namespace seastar;
+using namespace net;
+using namespace memcache;
+
+using parser_type = memcache_ascii_parser;
+
+static packet make_packet(std::vector<std::string> chunks, size_t buffer_size) {
+    packet p;
+    for (auto&& chunk : chunks) {
+        size_t size = chunk.size();
+        for (size_t pos = 0; pos < size; pos += buffer_size) {
+            auto now = std::min(pos + buffer_size, chunk.size()) - pos;
+            p.append(packet(chunk.data() + pos, now));
+        }
+    }
+    return p;
+}
+
+static auto make_input_stream(packet&& p) {
+    return input_stream<char>(data_source(
+            std::make_unique<packet_data_source>(std::move(p))));
+}
+
+static auto parse(packet&& p) {
+    auto is = make_lw_shared<input_stream<char>>(make_input_stream(std::move(p)));
+    auto parser = make_lw_shared<parser_type>();
+    parser->init();
+    return is->consume(*parser).then([is, parser] {
+        return make_ready_future<lw_shared_ptr<parser_type>>(parser);
+    });
+}
+
+auto for_each_fragment_size = [] (auto&& func) {
+    auto buffer_sizes = { 100000, 1000, 100, 10, 5, 2, 1 };
+    return do_for_each(buffer_sizes.begin(), buffer_sizes.end(), [func] (size_t buffer_size) {
+        return func([buffer_size] (std::vector<std::string> chunks) {
+            return make_packet(chunks, buffer_size);
+        });
+    });
+};
+
+SEASTAR_TEST_CASE(test_set_command_is_parsed) {
+    return for_each_fragment_size([] (auto make_packet) {
+        return parse(make_packet({"set key 1 2 3\r\nabc\r\n"})).then([] (auto p) {
+            BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+            BOOST_REQUIRE(p->_flags_str == "1");
+            BOOST_REQUIRE(p->_expiration == 2);
+            BOOST_REQUIRE(p->_size == 3);
+            BOOST_REQUIRE(p->_size_str == "3");
+            BOOST_REQUIRE(p->_key.key() == "key");
+            BOOST_REQUIRE(p->_blob == "abc");
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_empty_data_is_parsed) {
+    return for_each_fragment_size([] (auto make_packet) {
+        return parse(make_packet({"set key 1 2 0\r\n\r\n"})).then([] (auto p) {
+            BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+            BOOST_REQUIRE(p->_flags_str == "1");
+            BOOST_REQUIRE(p->_expiration == 2);
+            BOOST_REQUIRE(p->_size == 0);
+            BOOST_REQUIRE(p->_size_str == "0");
+            BOOST_REQUIRE(p->_key.key() == "key");
+            BOOST_REQUIRE(p->_blob == "");
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_superflous_data_is_an_error) {
+    return for_each_fragment_size([] (auto make_packet) {
+        return parse(make_packet({"set key 0 0 0\r\nasd\r\n"})).then([] (auto p) {
+            BOOST_REQUIRE(p->_state == parser_type::state::error);
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_not_enough_data_is_an_error) {
+    return for_each_fragment_size([] (auto make_packet) {
+        return parse(make_packet({"set key 0 0 3\r\n"})).then([] (auto p) {
+            BOOST_REQUIRE(p->_state == parser_type::state::error);
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_u32_parsing) {
+    return for_each_fragment_size([] (auto make_packet) {
+        return make_ready_future<>().then([make_packet] {
+            return parse(make_packet({"set key 0 0 0\r\n\r\n"})).then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_flags_str == "0");
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key 12345 0 0\r\n\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_flags_str == "12345");
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key -1 0 0\r\n\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::error);
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key 1-1 0 0\r\n\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::error);
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key " + std::to_string(std::numeric_limits<uint32_t>::max()) + " 0 0\r\n\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_flags_str == to_sstring(std::numeric_limits<uint32_t>::max()));
+            });
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_parsing_of_split_data) {
+    return for_each_fragment_size([] (auto make_packet) {
+        return make_ready_future<>()
+                .then([make_packet] {
+            return parse(make_packet({"set key 11", "1 222 3\r\nasd\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_key.key() == "key");
+                BOOST_REQUIRE(p->_flags_str == "111");
+                BOOST_REQUIRE(p->_expiration == 222);
+                BOOST_REQUIRE(p->_size == 3);
+                BOOST_REQUIRE(p->_size_str == "3");
+                BOOST_REQUIRE(p->_blob == "asd");
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key 11", "1 22", "2 3", "\r\nasd\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_key.key() == "key");
+                BOOST_REQUIRE(p->_flags_str == "111");
+                BOOST_REQUIRE(p->_expiration == 222);
+                BOOST_REQUIRE(p->_size == 3);
+                BOOST_REQUIRE(p->_size_str == "3");
+                BOOST_REQUIRE(p->_blob == "asd");
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set k", "ey 11", "1 2", "2", "2 3", "\r\nasd\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_key.key() == "key");
+                BOOST_REQUIRE(p->_flags_str == "111");
+                BOOST_REQUIRE(p->_expiration == 222);
+                BOOST_REQUIRE(p->_size == 3);
+                BOOST_REQUIRE(p->_size_str == "3");
+                BOOST_REQUIRE(p->_blob == "asd");
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key 111 222 3\r\n", "asd\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_key.key() == "key");
+                BOOST_REQUIRE(p->_flags_str == "111");
+                BOOST_REQUIRE(p->_expiration == 222);
+                BOOST_REQUIRE(p->_size == 3);
+                BOOST_REQUIRE(p->_size_str == "3");
+                BOOST_REQUIRE(p->_blob == "asd");
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key 111 222 3\r\na", "sd\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_key.key() == "key");
+                BOOST_REQUIRE(p->_flags_str == "111");
+                BOOST_REQUIRE(p->_expiration == 222);
+                BOOST_REQUIRE(p->_size == 3);
+                BOOST_REQUIRE(p->_size_str == "3");
+                BOOST_REQUIRE(p->_blob == "asd");
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key 111 222 3\r\nasd", "\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_key.key() == "key");
+                BOOST_REQUIRE(p->_flags_str == "111");
+                BOOST_REQUIRE(p->_expiration == 222);
+                BOOST_REQUIRE(p->_size == 3);
+                BOOST_REQUIRE(p->_size_str == "3");
+                BOOST_REQUIRE(p->_blob == "asd");
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"set key 111 222 3\r\nasd\r", "\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_key.key() == "key");
+                BOOST_REQUIRE(p->_flags_str == "111");
+                BOOST_REQUIRE(p->_expiration == 222);
+                BOOST_REQUIRE(p->_size == 3);
+                BOOST_REQUIRE(p->_size_str == "3");
+                BOOST_REQUIRE(p->_blob == "asd");
+            });
+        });
+    });
+}
+
+static std::vector<sstring> as_strings(std::vector<item_key>& keys) {
+    std::vector<sstring> v;
+    for (auto&& key : keys) {
+        v.push_back(key.key());
+    }
+    return v;
+}
+
+SEASTAR_TEST_CASE(test_get_parsing) {
+    return for_each_fragment_size([] (auto make_packet) {
+        return make_ready_future<>()
+                .then([make_packet] {
+            return parse(make_packet({"get key1\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_get);
+                BOOST_REQUIRE_EQUAL(as_strings(p->_keys), std::vector<sstring>({"key1"}));
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"get key1 key2\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_get);
+                BOOST_REQUIRE_EQUAL(as_strings(p->_keys), std::vector<sstring>({"key1", "key2"}));
+            });
+        }).then([make_packet] {
+            return parse(make_packet({"get key1 key2 key3\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_get);
+                BOOST_REQUIRE_EQUAL(as_strings(p->_keys), std::vector<sstring>({"key1", "key2", "key3"}));
+            });
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_catches_errors_in_get) {
+    return for_each_fragment_size([] (auto make_packet) {
+        return make_ready_future<>()
+                .then([make_packet] {
+            return parse(make_packet({"get\r\n"}))
+                    .then([] (auto p) {
+                BOOST_REQUIRE(p->_state == parser_type::state::error);
+            });
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_parser_returns_eof_state_when_no_command_follows) {
+    return for_each_fragment_size([] (auto make_packet) {
+        auto p = make_shared<parser_type>();
+        auto is = make_shared<input_stream<char>>(make_input_stream(make_packet({"get key\r\n"})));
+        p->init();
+        return is->consume(*p).then([p] {
+            BOOST_REQUIRE(p->_state == parser_type::state::cmd_get);
+        }).then([is, p] {
+            p->init();
+            return is->consume(*p).then([p, is] {
+                BOOST_REQUIRE(p->_state == parser_type::state::eof);
+            });
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_incomplete_command_is_an_error) {
+    return for_each_fragment_size([] (auto make_packet) {
+        auto p = make_shared<parser_type>();
+        auto is = make_shared<input_stream<char>>(make_input_stream(make_packet({"get"})));
+        p->init();
+        return is->consume(*p).then([p] {
+            BOOST_REQUIRE(p->_state == parser_type::state::error);
+        }).then([is, p] {
+            p->init();
+            return is->consume(*p).then([p, is] {
+                BOOST_REQUIRE(p->_state == parser_type::state::eof);
+            });
+        });
+    });
+}
+
+SEASTAR_TEST_CASE(test_multiple_requests_in_one_stream) {
+    return for_each_fragment_size([] (auto make_packet) {
+        auto p = make_shared<parser_type>();
+        auto is = make_shared<input_stream<char>>(make_input_stream(make_packet({"set key1 1 1 5\r\ndata1\r\nset key2 2 2 6\r\ndata2+\r\n"})));
+        p->init();
+        return is->consume(*p).then([p] {
+            BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+            BOOST_REQUIRE(p->_key.key() == "key1");
+            BOOST_REQUIRE(p->_flags_str == "1");
+            BOOST_REQUIRE(p->_expiration == 1);
+            BOOST_REQUIRE(p->_size == 5);
+            BOOST_REQUIRE(p->_size_str == "5");
+            BOOST_REQUIRE(p->_blob == "data1");
+        }).then([is, p] {
+            p->init();
+            return is->consume(*p).then([p, is] {
+                BOOST_REQUIRE(p->_state == parser_type::state::cmd_set);
+                BOOST_REQUIRE(p->_key.key() == "key2");
+                BOOST_REQUIRE(p->_flags_str == "2");
+                BOOST_REQUIRE(p->_expiration == 2);
+                BOOST_REQUIRE(p->_size == 6);
+                BOOST_REQUIRE(p->_size_str == "6");
+                BOOST_REQUIRE(p->_blob == "data2+");
+            });
+        });
+    });
+}
diff --git a/src/seastar/apps/memcached/tests/test_memcached.py b/src/seastar/apps/memcached/tests/test_memcached.py
new file mode 100755
index 00000000..4aca858e
--- /dev/null
+++ b/src/seastar/apps/memcached/tests/test_memcached.py
@@ -0,0 +1,600 @@
+#!/usr/bin/env python3
+#
+# 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.
+#
+from contextlib import contextmanager
+import socket
+import struct
+import sys
+import random
+import argparse
+import time
+import re
+import unittest
+
+server_addr = None
+call = None
+args = None
+
+class TimeoutError(Exception):
+    pass
+
+@contextmanager
+def tcp_connection(timeout=1):
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    s.settimeout(timeout)
+    s.connect(server_addr)
+    def call(msg):
+        s.send(msg.encode())
+        return s.recv(16*1024)
+    yield call
+    s.close()
+
+def slow(f):
+    def wrapper(self):
+        if args.fast:
+            raise unittest.SkipTest('Slow')
+        return f(self)
+    return wrapper
+
+def recv_all(s):
+    m = b''
+    while True:
+        data = s.recv(1024)
+        if not data:
+            break
+        m += data
+    return m
+
+def tcp_call(msg, timeout=1):
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    s.settimeout(timeout)
+    s.connect(server_addr)
+    s.send(msg.encode())
+    s.shutdown(socket.SHUT_WR)
+    data = recv_all(s)
+    s.close()
+    return data
+
+def udp_call_for_fragments(msg, timeout=1):
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    sock.settimeout(timeout)
+    this_req_id = random.randint(-32768, 32767)
+
+    datagram = struct.pack(">hhhh", this_req_id, 0, 1, 0) + msg.encode()
+    sock.sendto(datagram, server_addr)
+
+    messages = {}
+    n_determined = None
+    while True:
+        data, addr = sock.recvfrom(1500)
+        req_id, seq, n, res = struct.unpack_from(">hhhh", data)
+        content = data[8:]
+
+        if n_determined and n_determined != n:
+            raise Exception('Inconsitent number of total messages, %d and %d' % (n_determined, n))
+        n_determined = n
+
+        if req_id != this_req_id:
+            raise Exception('Invalid request id: ' + req_id + ', expected ' + this_req_id)
+
+        if seq in messages:
+            raise Exception('Duplicate message for seq=' + seq)
+
+        messages[seq] = content
+        if len(messages) == n:
+            break
+
+    for k, v in sorted(messages.items(), key=lambda e: e[0]):
+        yield v
+
+    sock.close()
+
+def udp_call(msg, **kwargs):
+    return b''.join(udp_call_for_fragments(msg, **kwargs))
+
+class MemcacheTest(unittest.TestCase):
+    def set(self, key, value, flags=0, expiry=0):
+        self.assertEqual(call('set %s %d %d %d\r\n%s\r\n' % (key, flags, expiry, len(value), value)), b'STORED\r\n')
+
+    def delete(self, key):
+        self.assertEqual(call('delete %s\r\n' % key), b'DELETED\r\n')
+
+    def assertHasKey(self, key):
+        resp = call('get %s\r\n' % key)
+        if not resp.startswith(('VALUE %s' % key).encode()):
+            self.fail('Key \'%s\' should be present, but got: %s' % (key, resp.decode()))
+
+    def assertNoKey(self, key):
+        resp = call('get %s\r\n' % key)
+        if resp != b'END\r\n':
+            self.fail('Key \'%s\' should not be present, but got: %s' % (key, resp.decode()))
+
+    def setKey(self, key):
+        self.set(key, 'some value')
+
+    def getItemVersion(self, key):
+        m = re.match(r'VALUE %s \d+ \d+ (?P<version>\d+)' % key, call('gets %s\r\n' % key).decode())
+        return int(m.group('version'))
+
+    def getStat(self, name, call_fn=None):
+        if not call_fn: call_fn = call
+        resp = call_fn('stats\r\n').decode()
+        m = re.search(r'STAT %s (?P<value>.+)' % re.escape(name), resp, re.MULTILINE)
+        return m.group('value')
+
+    def flush(self):
+        self.assertEqual(call('flush_all\r\n'), b'OK\r\n')
+
+    def tearDown(self):
+        self.flush()
+
+class TcpSpecificTests(MemcacheTest):
+    def test_recovers_from_errors_in_the_stream(self):
+        with tcp_connection() as conn:
+            self.assertEqual(conn('get\r\n'), b'ERROR\r\n')
+            self.assertEqual(conn('get key\r\n'), b'END\r\n')
+
+    def test_incomplete_command_results_in_error(self):
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.connect(server_addr)
+        s.send(b'get')
+        s.shutdown(socket.SHUT_WR)
+        self.assertEqual(recv_all(s), b'ERROR\r\n')
+        s.close()
+
+    def test_stream_closed_results_in_error(self):
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.connect(server_addr)
+        s.shutdown(socket.SHUT_WR)
+        self.assertEqual(recv_all(s), b'')
+        s.close()
+
+    def test_unsuccesful_parsing_does_not_leave_data_behind(self):
+        with tcp_connection() as conn:
+            self.assertEqual(conn('set key 0 0 5\r\nhello\r\n'), b'STORED\r\n')
+            self.assertRegex(conn('delete a b c\r\n'), b'^(CLIENT_)?ERROR.*\r\n$')
+            self.assertEqual(conn('get key\r\n'), b'VALUE key 0 5\r\nhello\r\nEND\r\n')
+            self.assertEqual(conn('delete key\r\n'), b'DELETED\r\n')
+
+    def test_flush_all_no_reply(self):
+        self.assertEqual(call('flush_all noreply\r\n'), b'')
+
+    def test_set_no_reply(self):
+        self.assertEqual(call('set key 0 0 5 noreply\r\nhello\r\nget key\r\n'), b'VALUE key 0 5\r\nhello\r\nEND\r\n')
+        self.delete('key')
+
+    def test_delete_no_reply(self):
+        self.setKey('key')
+        self.assertEqual(call('delete key noreply\r\nget key\r\n'), b'END\r\n')
+
+    def test_add_no_reply(self):
+        self.assertEqual(call('add key 0 0 1 noreply\r\na\r\nget key\r\n'), b'VALUE key 0 1\r\na\r\nEND\r\n')
+        self.delete('key')
+
+    def test_replace_no_reply(self):
+        self.assertEqual(call('set key 0 0 1\r\na\r\n'), b'STORED\r\n')
+        self.assertEqual(call('replace key 0 0 1 noreply\r\nb\r\nget key\r\n'), b'VALUE key 0 1\r\nb\r\nEND\r\n')
+        self.delete('key')
+
+    def test_cas_noreply(self):
+        self.assertNoKey('key')
+        self.assertEqual(call('cas key 0 0 1 1 noreply\r\na\r\n'), b'')
+        self.assertNoKey('key')
+
+        self.assertEqual(call('add key 0 0 5\r\nhello\r\n'), b'STORED\r\n')
+        version = self.getItemVersion('key')
+
+        self.assertEqual(call('cas key 1 0 5 %d noreply\r\naloha\r\n' % (version + 1)), b'')
+        self.assertEqual(call('get key\r\n'), b'VALUE key 0 5\r\nhello\r\nEND\r\n')
+
+        self.assertEqual(call('cas key 1 0 5 %d noreply\r\naloha\r\n' % (version)), b'')
+        self.assertEqual(call('get key\r\n'), b'VALUE key 1 5\r\naloha\r\nEND\r\n')
+
+        self.delete('key')
+
+    @slow
+    def test_connection_statistics(self):
+        with tcp_connection() as conn:
+            curr_connections = int(self.getStat('curr_connections', call_fn=conn))
+            total_connections = int(self.getStat('total_connections', call_fn=conn))
+            with tcp_connection() as conn2:
+                self.assertEqual(curr_connections + 1, int(self.getStat('curr_connections', call_fn=conn)))
+                self.assertEqual(total_connections + 1, int(self.getStat('total_connections', call_fn=conn)))
+            self.assertEqual(total_connections + 1, int(self.getStat('total_connections', call_fn=conn)))
+            time.sleep(0.1)
+            self.assertEqual(curr_connections, int(self.getStat('curr_connections', call_fn=conn)))
+
+class UdpSpecificTests(MemcacheTest):
+    def test_large_response_is_split_into_mtu_chunks(self):
+        max_datagram_size = 1400
+        data = '1' * (max_datagram_size*3)
+        self.set('key', data)
+
+        chunks = list(udp_call_for_fragments('get key\r\n'))
+
+        for chunk in chunks:
+            self.assertLessEqual(len(chunk), max_datagram_size)
+
+        self.assertEqual(b''.join(chunks).decode(),
+            'VALUE key 0 %d\r\n%s\r\n' \
+            'END\r\n' % (len(data), data))
+
+        self.delete('key')
+
+class TestCommands(MemcacheTest):
+    def test_basic_commands(self):
+        self.assertEqual(call('get key\r\n'), b'END\r\n')
+        self.assertEqual(call('set key 0 0 5\r\nhello\r\n'), b'STORED\r\n')
+        self.assertEqual(call('get key\r\n'), b'VALUE key 0 5\r\nhello\r\nEND\r\n')
+        self.assertEqual(call('delete key\r\n'), b'DELETED\r\n')
+        self.assertEqual(call('delete key\r\n'), b'NOT_FOUND\r\n')
+        self.assertEqual(call('get key\r\n'), b'END\r\n')
+
+    def test_error_handling(self):
+        self.assertEqual(call('get\r\n'), b'ERROR\r\n')
+
+    @slow
+    def test_expiry(self):
+        self.assertEqual(call('set key 0 1 5\r\nhello\r\n'), b'STORED\r\n')
+        self.assertEqual(call('get key\r\n'), b'VALUE key 0 5\r\nhello\r\nEND\r\n')
+        time.sleep(2)
+        self.assertEqual(call('get key\r\n'), b'END\r\n')
+
+    @slow
+    def test_expiry_at_epoch_time(self):
+        expiry = int(time.time()) + 1
+        self.assertEqual(call('set key 0 %d 5\r\nhello\r\n' % expiry), b'STORED\r\n')
+        self.assertEqual(call('get key\r\n'), b'VALUE key 0 5\r\nhello\r\nEND\r\n')
+        time.sleep(2)
+        self.assertEqual(call('get key\r\n'), b'END\r\n')
+
+    def test_multiple_keys_in_get(self):
+        self.assertEqual(call('set key1 0 0 2\r\nv1\r\n'), b'STORED\r\n')
+        self.assertEqual(call('set key 0 0 2\r\nv2\r\n'), b'STORED\r\n')
+        resp = call('get key1 key\r\n')
+        self.assertRegex(resp, b'^(VALUE key1 0 2\r\nv1\r\nVALUE key 0 2\r\nv2\r\nEND\r\n)|(VALUE key 0 2\r\nv2\r\nVALUE key1 0 2\r\nv1\r\nEND\r\n)$')
+        self.delete("key")
+        self.delete("key1")
+
+    def test_flush_all(self):
+        self.set('key', 'value')
+        self.assertEqual(call('flush_all\r\n'), b'OK\r\n')
+        self.assertNoKey('key')
+
+    def test_keys_set_after_flush_remain(self):
+        self.assertEqual(call('flush_all\r\n'), b'OK\r\n')
+        self.setKey('key')
+        self.assertHasKey('key')
+        self.delete('key')
+
+    @slow
+    def test_flush_all_with_timeout_flushes_all_keys_even_those_set_after_flush(self):
+        self.setKey('key')
+        self.assertEqual(call('flush_all 2\r\n'), b'OK\r\n')
+        self.assertHasKey('key')
+        self.setKey('key2')
+        time.sleep(3)
+        self.assertNoKey('key')
+        self.assertNoKey('key2')
+
+    @slow
+    def test_subsequent_flush_is_merged(self):
+        self.setKey('key')
+        self.assertEqual(call('flush_all 2\r\n'), b'OK\r\n') # Can flush in anything between 1-2
+        self.assertEqual(call('flush_all 4\r\n'), b'OK\r\n') # Can flush in anything between 3-4
+        time.sleep(3)
+        self.assertHasKey('key')
+        self.setKey('key2')
+        time.sleep(4)
+        self.assertNoKey('key')
+        self.assertNoKey('key2')
+
+    @slow
+    def test_immediate_flush_cancels_delayed_flush(self):
+        self.assertEqual(call('flush_all 2\r\n'), b'OK\r\n')
+        self.assertEqual(call('flush_all\r\n'), b'OK\r\n')
+        self.setKey('key')
+        time.sleep(1)
+        self.assertHasKey('key')
+        self.delete('key')
+
+    @slow
+    def test_flushing_in_the_past(self):
+        self.setKey('key1')
+        time.sleep(1)
+        self.setKey('key2')
+        key2_time = int(time.time())
+        self.assertEqual(call('flush_all %d\r\n' % (key2_time - 1)), b'OK\r\n')
+        time.sleep(1)
+        self.assertNoKey("key1")
+        self.assertNoKey("key2")
+
+    @slow
+    def test_memcache_does_not_crash_when_flushing_with_already_expred_items(self):
+        self.assertEqual(call('set key1 0 2 5\r\nhello\r\n'), b'STORED\r\n')
+        time.sleep(1)
+        self.assertEqual(call('flush_all\r\n'), b'OK\r\n')
+
+    def test_response_spanning_many_datagrams(self):
+        key1_data = '1' * 1000
+        key2_data = '2' * 1000
+        key3_data = '3' * 1000
+        self.set('key1', key1_data)
+        self.set('key2', key2_data)
+        self.set('key3', key3_data)
+
+        resp = call('get key1 key2 key3\r\n').decode()
+
+        pattern = '^VALUE (?P<v1>.*?\r\n.*?)\r\nVALUE (?P<v2>.*?\r\n.*?)\r\nVALUE (?P<v3>.*?\r\n.*?)\r\nEND\r\n$'
+        self.assertRegex(resp, pattern)
+
+        m = re.match(pattern, resp)
+        self.assertEqual(set([m.group('v1'), m.group('v2'), m.group('v3')]),
+            set(['key1 0 %d\r\n%s' % (len(key1_data), key1_data),
+                'key2 0 %d\r\n%s' % (len(key2_data), key2_data),
+                'key3 0 %d\r\n%s' % (len(key3_data), key3_data)]))
+
+        self.delete('key1')
+        self.delete('key2')
+        self.delete('key3')
+
+    def test_version(self):
+        self.assertRegex(call('version\r\n'), b'^VERSION .*\r\n$')
+
+    def test_add(self):
+        self.assertEqual(call('add key 0 0 1\r\na\r\n'), b'STORED\r\n')
+        self.assertEqual(call('add key 0 0 1\r\na\r\n'), b'NOT_STORED\r\n')
+        self.delete('key')
+
+    def test_replace(self):
+        self.assertEqual(call('add key 0 0 1\r\na\r\n'), b'STORED\r\n')
+        self.assertEqual(call('replace key 0 0 1\r\na\r\n'), b'STORED\r\n')
+        self.delete('key')
+        self.assertEqual(call('replace key 0 0 1\r\na\r\n'), b'NOT_STORED\r\n')
+
+    def test_cas_and_gets(self):
+        self.assertEqual(call('cas key 0 0 1 1\r\na\r\n'), b'NOT_FOUND\r\n')
+        self.assertEqual(call('add key 0 0 5\r\nhello\r\n'), b'STORED\r\n')
+        version = self.getItemVersion('key')
+
+        self.assertEqual(call('set key 1 0 5\r\nhello\r\n'), b'STORED\r\n')
+        self.assertEqual(call('gets key\r\n').decode(), 'VALUE key 1 5 %d\r\nhello\r\nEND\r\n' % (version + 1))
+
+        self.assertEqual(call('cas key 0 0 5 %d\r\nhello\r\n' % (version)), b'EXISTS\r\n')
+        self.assertEqual(call('cas key 0 0 5 %d\r\naloha\r\n' % (version + 1)), b'STORED\r\n')
+        self.assertEqual(call('gets key\r\n').decode(), 'VALUE key 0 5 %d\r\naloha\r\nEND\r\n' % (version + 2))
+
+        self.delete('key')
+
+    def test_curr_items_stat(self):
+        self.assertEqual(0, int(self.getStat('curr_items')))
+        self.setKey('key')
+        self.assertEqual(1, int(self.getStat('curr_items')))
+        self.delete('key')
+        self.assertEqual(0, int(self.getStat('curr_items')))
+
+    def test_how_stats_change_with_different_commands(self):
+        get_count = int(self.getStat('cmd_get'))
+        set_count = int(self.getStat('cmd_set'))
+        flush_count = int(self.getStat('cmd_flush'))
+        total_items = int(self.getStat('total_items'))
+        get_misses = int(self.getStat('get_misses'))
+        get_hits = int(self.getStat('get_hits'))
+        cas_hits = int(self.getStat('cas_hits'))
+        cas_badval = int(self.getStat('cas_badval'))
+        cas_misses = int(self.getStat('cas_misses'))
+        delete_misses = int(self.getStat('delete_misses'))
+        delete_hits = int(self.getStat('delete_hits'))
+        curr_connections = int(self.getStat('curr_connections'))
+        incr_hits = int(self.getStat('incr_hits'))
+        incr_misses = int(self.getStat('incr_misses'))
+        decr_hits = int(self.getStat('decr_hits'))
+        decr_misses = int(self.getStat('decr_misses'))
+
+        call('get key\r\n')
+        get_count += 1
+        get_misses += 1
+
+        call('gets key\r\n')
+        get_count += 1
+        get_misses += 1
+
+        call('set key1 0 0 1\r\na\r\n')
+        set_count += 1
+        total_items += 1
+
+        call('get key1\r\n')
+        get_count += 1
+        get_hits += 1
+
+        call('add key1 0 0 1\r\na\r\n')
+        set_count += 1
+
+        call('add key2 0 0 1\r\na\r\n')
+        set_count += 1
+        total_items += 1
+
+        call('replace key1 0 0 1\r\na\r\n')
+        set_count += 1
+        total_items += 1
+
+        call('replace key3 0 0 1\r\na\r\n')
+        set_count += 1
+
+        call('cas key4 0 0 1 1\r\na\r\n')
+        set_count += 1
+        cas_misses += 1
+
+        call('cas key1 0 0 1 %d\r\na\r\n' % self.getItemVersion('key1'))
+        set_count += 1
+        get_count += 1
+        get_hits += 1
+        cas_hits += 1
+        total_items += 1
+
+        call('cas key1 0 0 1 %d\r\na\r\n' % (self.getItemVersion('key1') + 1))
+        set_count += 1
+        get_count += 1
+        get_hits += 1
+        cas_badval += 1
+
+        call('delete key1\r\n')
+        delete_hits += 1
+
+        call('delete key1\r\n')
+        delete_misses += 1
+
+        call('incr num 1\r\n')
+        incr_misses += 1
+        call('decr num 1\r\n')
+        decr_misses += 1
+
+        call('set num 0 0 1\r\n0\r\n')
+        set_count += 1
+        total_items += 1
+
+        call('incr num 1\r\n')
+        incr_hits += 1
+        call('decr num 1\r\n')
+        decr_hits += 1
+
+        self.flush()
+        flush_count += 1
+
+        self.assertEqual(get_count, int(self.getStat('cmd_get')))
+        self.assertEqual(set_count, int(self.getStat('cmd_set')))
+        self.assertEqual(flush_count, int(self.getStat('cmd_flush')))
+        self.assertEqual(total_items, int(self.getStat('total_items')))
+        self.assertEqual(get_hits, int(self.getStat('get_hits')))
+        self.assertEqual(get_misses, int(self.getStat('get_misses')))
+        self.assertEqual(cas_misses, int(self.getStat('cas_misses')))
+        self.assertEqual(cas_hits, int(self.getStat('cas_hits')))
+        self.assertEqual(cas_badval, int(self.getStat('cas_badval')))
+        self.assertEqual(delete_misses, int(self.getStat('delete_misses')))
+        self.assertEqual(delete_hits, int(self.getStat('delete_hits')))
+        self.assertEqual(0, int(self.getStat('curr_items')))
+        self.assertEqual(curr_connections, int(self.getStat('curr_connections')))
+        self.assertEqual(incr_misses, int(self.getStat('incr_misses')))
+        self.assertEqual(incr_hits, int(self.getStat('incr_hits')))
+        self.assertEqual(decr_misses, int(self.getStat('decr_misses')))
+        self.assertEqual(decr_hits, int(self.getStat('decr_hits')))
+
+    def test_incr(self):
+        self.assertEqual(call('incr key 0\r\n'), b'NOT_FOUND\r\n')
+
+        self.assertEqual(call('set key 0 0 1\r\n0\r\n'), b'STORED\r\n')
+        self.assertEqual(call('incr key 0\r\n'), b'0\r\n')
+        self.assertEqual(call('get key\r\n'), b'VALUE key 0 1\r\n0\r\nEND\r\n')
+
+        self.assertEqual(call('incr key 1\r\n'), b'1\r\n')
+        self.assertEqual(call('incr key 2\r\n'), b'3\r\n')
+        self.assertEqual(call('incr key %d\r\n' % (pow(2, 64) - 1)), b'2\r\n')
+        self.assertEqual(call('incr key %d\r\n' % (pow(2, 64) - 3)), b'18446744073709551615\r\n')
+        self.assertRegex(call('incr key 1\r\n').decode(), r'0(\w+)?\r\n')
+
+        self.assertEqual(call('set key 0 0 2\r\n1 \r\n'), b'STORED\r\n')
+        self.assertEqual(call('incr key 1\r\n'), b'2\r\n')
+
+        self.assertEqual(call('set key 0 0 2\r\n09\r\n'), b'STORED\r\n')
+        self.assertEqual(call('incr key 1\r\n'), b'10\r\n')
+
+    def test_decr(self):
+        self.assertEqual(call('decr key 0\r\n'), b'NOT_FOUND\r\n')
+
+        self.assertEqual(call('set key 0 0 1\r\n7\r\n'), b'STORED\r\n')
+        self.assertEqual(call('decr key 1\r\n'), b'6\r\n')
+        self.assertEqual(call('get key\r\n'), b'VALUE key 0 1\r\n6\r\nEND\r\n')
+
+        self.assertEqual(call('decr key 6\r\n'), b'0\r\n')
+        self.assertEqual(call('decr key 2\r\n'), b'0\r\n')
+
+        self.assertEqual(call('set key 0 0 2\r\n20\r\n'), b'STORED\r\n')
+        self.assertRegex(call('decr key 11\r\n').decode(), r'^9( )?\r\n$')
+
+        self.assertEqual(call('set key 0 0 3\r\n100\r\n'), b'STORED\r\n')
+        self.assertRegex(call('decr key 91\r\n').decode(), r'^9(  )?\r\n$')
+
+        self.assertEqual(call('set key 0 0 2\r\n1 \r\n'), b'STORED\r\n')
+        self.assertEqual(call('decr key 1\r\n'), b'0\r\n')
+
+        self.assertEqual(call('set key 0 0 2\r\n09\r\n'), b'STORED\r\n')
+        self.assertEqual(call('decr key 1\r\n'), b'8\r\n')
+
+    def test_incr_and_decr_on_invalid_input(self):
+        error_msg = b'CLIENT_ERROR cannot increment or decrement non-numeric value\r\n'
+        for cmd in ['incr', 'decr']:
+            for value in ['', '-1', 'a', '0x1', '18446744073709551616']:
+                self.assertEqual(call('set key 0 0 %d\r\n%s\r\n' % (len(value), value)), b'STORED\r\n')
+                prev = call('get key\r\n')
+                self.assertEqual(call(cmd + ' key 1\r\n'), error_msg, "cmd=%s, value=%s" % (cmd, value))
+                self.assertEqual(call('get key\r\n'), prev)
+                self.delete('key')
+
+def wait_for_memcache_tcp(timeout=4):
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    timeout_at = time.time() + timeout
+    while True:
+        if time.time() >= timeout_at:
+            raise TimeoutError()
+        try:
+            s.connect(server_addr)
+            s.close()
+            break
+        except ConnectionRefusedError:
+            time.sleep(0.1)
+
+
+def wait_for_memcache_udp(timeout=4):
+    timeout_at = time.time() + timeout
+    while True:
+        if time.time() >= timeout_at:
+            raise TimeoutError()
+        try:
+            udp_call('version\r\n', timeout=0.2)
+            break
+        except socket.timeout:
+            pass
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description="memcache protocol tests")
+    parser.add_argument('--server', '-s', action="store", help="server adddress in <host>:<port> format", default="localhost:11211")
+    parser.add_argument('--udp', '-U', action="store_true", help="Use UDP protocol")
+    parser.add_argument('--fast',  action="store_true", help="Run only fast tests")
+    args = parser.parse_args()
+
+    host, port = args.server.split(':')
+    server_addr = (host, int(port))
+
+    if args.udp:
+        call = udp_call
+        wait_for_memcache_udp()
+    else:
+        call = tcp_call
+        wait_for_memcache_tcp()
+
+    runner = unittest.TextTestRunner()
+    loader = unittest.TestLoader()
+    suite = unittest.TestSuite()
+    suite.addTest(loader.loadTestsFromTestCase(TestCommands))
+    if args.udp:
+        suite.addTest(loader.loadTestsFromTestCase(UdpSpecificTests))
+    else:
+        suite.addTest(loader.loadTestsFromTestCase(TcpSpecificTests))
+    result = runner.run(suite)
+    if not result.wasSuccessful():
+        sys.exit(1)