Merge pull request #9409 from clemrodriguez/mysqlxx-share-connection

Mysqlxx share connection for external dictionaries only

base/mysqlxx/CMakeLists.txt

@@ -8,6 +8,7 @@ add_library (mysqlxx
     src/Row.cpp
     src/Value.cpp
     src/Pool.cpp
+    src/PoolFactory.cpp
     src/PoolWithFailover.cpp
 
     include/mysqlxx/Connection.h
@@ -15,6 +16,7 @@ add_library (mysqlxx
     include/mysqlxx/mysqlxx.h
     include/mysqlxx/Null.h
     include/mysqlxx/Pool.h
+    include/mysqlxx/PoolFactory.h
     include/mysqlxx/PoolWithFailover.h
     include/mysqlxx/Query.h
     include/mysqlxx/ResultBase.h

base/mysqlxx/include/mysqlxx/Pool.h

@@ -198,6 +198,8 @@ public:
         return description;
     }
 
+    void removeConnection(Connection* data);
+
 protected:
     /// Number of MySQL connections which are created at launch.
     unsigned default_connections;

base/mysqlxx/include/mysqlxx/PoolFactory.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include <mutex>
+#include <memory>
+#include <boost/noncopyable.hpp>
+
+#include <mysqlxx/PoolWithFailover.h>
+
+
+#define MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_START_CONNECTIONS 1
+#define MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_CONNECTIONS 16
+#define MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_TRIES 3
+
+
+namespace mysqlxx
+{
+
+/*
+ * PoolFactory.h
+ * This class is a helper singleton to mutualize connections to MySQL.
+ */
+class PoolFactory final : private boost::noncopyable
+{
+public:
+    static PoolFactory & instance();
+
+    PoolFactory(const PoolFactory &) = delete;
+
+    /** Allocates a PoolWithFailover to connect to MySQL. */
+    PoolWithFailover Get(const std::string & config_name,
+        unsigned default_connections = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_START_CONNECTIONS,
+        unsigned max_connections = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_CONNECTIONS,
+        size_t max_tries = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_TRIES);
+
+    /** Allocates a PoolWithFailover to connect to MySQL. */
+    PoolWithFailover Get(const Poco::Util::AbstractConfiguration & config,
+        const std::string & config_name,
+        unsigned default_connections = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_START_CONNECTIONS,
+        unsigned max_connections = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_CONNECTIONS,
+        size_t max_tries = MYSQLXX_POOL_WITH_FAILOVER_DEFAULT_MAX_TRIES);
+
+    void reset();
+
+
+    ~PoolFactory() = default;
+    PoolFactory& operator=(const PoolFactory &) = delete;
+
+private:
+    PoolFactory();
+
+    struct Impl;
+    std::unique_ptr<Impl> impl;
+};
+
+}

base/mysqlxx/include/mysqlxx/PoolWithFailover.h

@@ -77,6 +77,10 @@ namespace mysqlxx
         size_t max_tries;
         /// Mutex for set of replicas.
         std::mutex mutex;
+        std::string config_name;
+
+        /// Can the Pool be shared
+        bool shareable;
 
     public:
         using Entry = Pool::Entry;
@@ -100,8 +104,6 @@ namespace mysqlxx
 
         PoolWithFailover(const PoolWithFailover & other);
 
-        PoolWithFailover & operator=(const PoolWithFailover &) = delete;
-
         /** Allocates a connection to use. */
         Entry Get();
     };

base/mysqlxx/include/mysqlxx/Value.h

@@ -239,7 +239,8 @@ template <> inline bool                 Value::get<bool                 >() cons
 template <> inline char                 Value::get<char                 >() const { return getInt(); }
 template <> inline signed char          Value::get<signed char          >() const { return getInt(); }
 template <> inline unsigned char        Value::get<unsigned char        >() const { return getUInt(); }
-template <> inline char8_t              Value::get<char8_t              >() const { return getUInt(); }
+// crodriguez uncomment
+//template <> inline char8_t              Value::get<char8_t              >() const { return getUInt(); }
 template <> inline short                Value::get<short                >() const { return getInt(); }
 template <> inline unsigned short       Value::get<unsigned short       >() const { return getUInt(); }
 template <> inline int                  Value::get<int                  >() const { return getInt(); }

base/mysqlxx/src/Pool.cpp

@@ -21,7 +21,8 @@ void Pool::Entry::incrementRefCount()
 {
     if (!data)
         return;
-    ++data->ref_count;
+    ++(data->ref_count);
+    if (data->ref_count==1)
         mysql_thread_init();
 }
 
@@ -29,8 +30,12 @@ void Pool::Entry::decrementRefCount()
 {
     if (!data)
         return;
-    --data->ref_count;
+    if (data->ref_count > 0)
+    {
+        --(data->ref_count);
+        if (data->ref_count==0)
             mysql_thread_end();
+    }
 }
 
 
@@ -169,14 +174,24 @@ Pool::Entry Pool::tryGet()
     return Entry();
 }
 
+void Pool::removeConnection(Connection* connection)
+{
+    std::lock_guard<std::mutex> lock(mutex);
+    if (connection)
+    {
+        if (connection->ref_count > 0)
+        {
+            connection->conn.disconnect();
+            connection->ref_count = 0;
+        }
+        connections.remove(connection);
+    }
+}
+
 
 void Pool::Entry::disconnect()
 {
-    if (data)
-    {
-        decrementRefCount();
-        data->conn.disconnect();
-    }
+    pool->removeConnection(data);
 }
 
 

base/mysqlxx/src/PoolFactory.cpp

@@ -0,0 +1,122 @@
+#include <mysqlxx/PoolFactory.h>
+#include <Poco/Util/Application.h>
+#include <Poco/Util/LayeredConfiguration.h>
+
+namespace mysqlxx
+{
+
+struct PoolFactory::Impl
+{
+    // Cache of already affected pools identified by their config name
+    std::map<std::string, std::shared_ptr<PoolWithFailover>> pools;
+
+    // Cache of Pool ID (host + port + user +...) cibling already established shareable pool
+    std::map<std::string, std::string> pools_by_ids;
+
+    /// Protect pools and pools_by_ids caches
+    std::mutex mutex;
+};
+
+PoolWithFailover PoolFactory::Get(const std::string & config_name, unsigned default_connections,
+    unsigned max_connections, size_t max_tries)
+{
+    return Get(Poco::Util::Application::instance().config(), config_name, default_connections, max_connections, max_tries);
+}
+
+/// Duplicate of code from StringUtils.h. Copied here for less dependencies.
+static bool startsWith(const std::string & s, const char * prefix)
+{
+    return s.size() >= strlen(prefix) && 0 == memcmp(s.data(), prefix, strlen(prefix));
+}
+
+static std::string getPoolEntryName(const Poco::Util::AbstractConfiguration & config,
+        const std::string & config_name)
+{
+    bool shared = config.getBool(config_name + ".share_connection", false);
+
+    // Not shared no need to generate a name the pool won't be stored
+    if (!shared)
+        return "";
+
+    std::string entry_name = "";
+    std::string host = config.getString(config_name + ".host", "");
+    std::string port = config.getString(config_name + ".port", "");
+    std::string user = config.getString(config_name + ".user", "");
+    std::string db = config.getString(config_name + ".db", "");
+    std::string table = config.getString(config_name + ".table", "");
+
+    Poco::Util::AbstractConfiguration::Keys keys;
+    config.keys(config_name, keys);
+
+    if (config.has(config_name + ".replica"))
+    {
+        Poco::Util::AbstractConfiguration::Keys replica_keys;
+        config.keys(config_name, replica_keys);
+        for (const auto & replica_config_key : replica_keys)
+        {
+            /// There could be another elements in the same level in configuration file, like "user", "port"...
+            if (startsWith(replica_config_key, "replica"))
+            {
+                std::string replica_name = config_name + "." + replica_config_key;
+                std::string tmp_host = config.getString(replica_name + ".host", host);
+                std::string tmp_port = config.getString(replica_name + ".port", port);
+                std::string tmp_user = config.getString(replica_name + ".user", user);
+                entry_name += (entry_name.empty() ? "" : "|") + tmp_user + "@" + tmp_host + ":" + tmp_port + "/" + db;
+            }
+        }
+    }
+    else
+    {
+        entry_name = user + "@" + host + ":" + port + "/" + db;
+    }
+    return entry_name;
+}
+
+PoolWithFailover PoolFactory::Get(const Poco::Util::AbstractConfiguration & config,
+        const std::string & config_name, unsigned default_connections, unsigned max_connections, size_t max_tries)
+{
+
+    std::lock_guard<std::mutex> lock(impl->mutex);
+    if (auto entry = impl->pools.find(config_name); entry != impl->pools.end())
+    {
+        return *(entry->second.get());
+    }
+    else
+    {
+        std::string entry_name = getPoolEntryName(config, config_name);
+        if (auto id = impl->pools_by_ids.find(entry_name); id != impl->pools_by_ids.end())
+        {
+            entry = impl->pools.find(id->second);
+            std::shared_ptr<PoolWithFailover> pool = entry->second;
+            impl->pools.insert_or_assign(config_name, pool);
+            return *pool;
+        }
+
+        auto pool = std::make_shared<PoolWithFailover>(config, config_name, default_connections, max_connections, max_tries);
+        // Check the pool will be shared
+        if (!entry_name.empty())
+        {
+            // Store shared pool
+            impl->pools.insert_or_assign(config_name, pool);
+            impl->pools_by_ids.insert_or_assign(entry_name, config_name);
+        }
+        return *(pool.get());
+    }
+}
+
+void PoolFactory::reset()
+{
+    std::lock_guard<std::mutex> lock(impl->mutex);
+    impl->pools.clear();
+    impl->pools_by_ids.clear();
+}
+
+PoolFactory::PoolFactory() : impl(std::make_unique<PoolFactory::Impl>()) {}
+
+PoolFactory & PoolFactory::instance()
+{
+    static PoolFactory ret;
+    return ret;
+}
+
+}

base/mysqlxx/src/PoolWithFailover.cpp

@@ -15,6 +15,7 @@ PoolWithFailover::PoolWithFailover(const Poco::Util::AbstractConfiguration & cfg
                                    const unsigned max_connections, const size_t max_tries)
     : max_tries(max_tries)
 {
+    shareable = cfg.getBool(config_name + ".share_connection", false);
     if (cfg.has(config_name + ".replica"))
     {
         Poco::Util::AbstractConfiguration::Keys replica_keys;
@@ -48,8 +49,14 @@ PoolWithFailover::PoolWithFailover(const std::string & config_name, const unsign
 {}
 
 PoolWithFailover::PoolWithFailover(const PoolWithFailover & other)
-    : max_tries{other.max_tries}
+    : max_tries{other.max_tries}, config_name{other.config_name}, shareable{other.shareable}
 {
+    if (shareable)
+    {
+        replicas_by_priority = other.replicas_by_priority;
+    }
+    else
+    {
         for (const auto & priority_replicas : other.replicas_by_priority)
         {
             Replicas replicas;
@@ -58,6 +65,7 @@ PoolWithFailover::PoolWithFailover(const PoolWithFailover & other)
                 replicas.emplace_back(std::make_shared<Pool>(*pool));
             replicas_by_priority.emplace(priority_replicas.first, std::move(replicas));
         }
+    }
 }
 
 PoolWithFailover::Entry PoolWithFailover::Get()
@@ -81,7 +89,7 @@ PoolWithFailover::Entry PoolWithFailover::Get()
 
                 try
                 {
-                    Entry entry = pool->tryGet();
+                    Entry entry = shareable ? pool->Get() : pool->tryGet();
 
                     if (!entry.isNull())
                     {

dbms/src/Dictionaries/MySQLDictionarySource.cpp

@@ -46,6 +46,7 @@ void registerDictionarySourceMysql(DictionarySourceFactory & factory)
 #    include <common/logger_useful.h>
 #    include <Formats/MySQLBlockInputStream.h>
 #    include "readInvalidateQuery.h"
+#    include <mysqlxx/PoolFactory.h>
 
 namespace DB
 {
@@ -66,11 +67,11 @@ MySQLDictionarySource::MySQLDictionarySource(
     , update_field{config.getString(config_prefix + ".update_field", "")}
     , dont_check_update_time{config.getBool(config_prefix + ".dont_check_update_time", false)}
     , sample_block{sample_block_}
-    , pool{config, config_prefix}
+    , pool{mysqlxx::PoolFactory::instance().Get(config, config_prefix)}
     , query_builder{dict_struct, db, table, where, IdentifierQuotingStyle::Backticks}
     , load_all_query{query_builder.composeLoadAllQuery()}
     , invalidate_query{config.getString(config_prefix + ".invalidate_query", "")}
-    , close_connection{config.getBool(config_prefix + ".close_connection", false)}
+    , close_connection{config.getBool(config_prefix + ".close_connection", false) || config.getBool(config_prefix + ".share_connection", false)}
 {
 }
 
@@ -114,19 +115,21 @@ std::string MySQLDictionarySource::getUpdateFieldAndDate()
 
 BlockInputStreamPtr MySQLDictionarySource::loadAll()
 {
-    last_modification = getLastModification();
+    auto connection = pool.Get();
+    last_modification = getLastModification(connection, false);
 
     LOG_TRACE(log, load_all_query);
-    return std::make_shared<MySQLBlockInputStream>(pool.Get(), load_all_query, sample_block, max_block_size, close_connection);
+    return std::make_shared<MySQLBlockInputStream>(connection, load_all_query, sample_block, max_block_size, close_connection);
 }
 
 BlockInputStreamPtr MySQLDictionarySource::loadUpdatedAll()
 {
-    last_modification = getLastModification();
+    auto connection = pool.Get();
+    last_modification = getLastModification(connection, false);
 
     std::string load_update_query = getUpdateFieldAndDate();
     LOG_TRACE(log, load_update_query);
-    return std::make_shared<MySQLBlockInputStream>(pool.Get(), load_update_query, sample_block, max_block_size, close_connection);
+    return std::make_shared<MySQLBlockInputStream>(connection, load_update_query, sample_block, max_block_size, close_connection);
 }
 
 BlockInputStreamPtr MySQLDictionarySource::loadIds(const std::vector<UInt64> & ids)
@@ -158,8 +161,8 @@ bool MySQLDictionarySource::isModified() const
 
     if (dont_check_update_time)
         return true;
-
-    return getLastModification() > last_modification;
+    auto connection = pool.Get();
+    return getLastModification(connection, true) > last_modification;
 }
 
 bool MySQLDictionarySource::supportsSelectiveLoad() const
@@ -199,7 +202,7 @@ std::string MySQLDictionarySource::quoteForLike(const std::string s)
     return out.str();
 }
 
-LocalDateTime MySQLDictionarySource::getLastModification() const
+LocalDateTime MySQLDictionarySource::getLastModification(mysqlxx::Pool::Entry & connection, bool allow_connection_closure) const
 {
     LocalDateTime modification_time{std::time(nullptr)};
 
@@ -208,7 +211,6 @@ LocalDateTime MySQLDictionarySource::getLastModification() const
 
     try
     {
-        auto connection = pool.Get();
         auto query = connection->query("SHOW TABLE STATUS LIKE " + quoteForLike(table));
 
         LOG_TRACE(log, query.str());
@@ -233,6 +235,11 @@ LocalDateTime MySQLDictionarySource::getLastModification() const
                 ++fetched_rows;
         }
 
+        if (close_connection && allow_connection_closure)
+        {
+            connection.disconnect();
+        }
+
         if (0 == fetched_rows)
             LOG_ERROR(log, "Cannot find table in SHOW TABLE STATUS result.");
 
@@ -243,7 +250,6 @@ LocalDateTime MySQLDictionarySource::getLastModification() const
     {
         tryLogCurrentException("MySQLDictionarySource");
     }
-
     /// we suppose failure to get modification time is not an error, therefore return current time
     return modification_time;
 }

dbms/src/Dictionaries/MySQLDictionarySource.h

@@ -62,7 +62,7 @@ private:
 
     static std::string quoteForLike(const std::string s);
 
-    LocalDateTime getLastModification() const;
+    LocalDateTime getLastModification(mysqlxx::Pool::Entry & connection, bool allow_connection_closure) const;
 
     // execute invalidate_query. expects single cell in result
     std::string doInvalidateQuery(const std::string & request) const;

dbms/src/Interpreters/ExternalDictionariesLoader.cpp

@@ -1,5 +1,10 @@
 #include <Interpreters/ExternalDictionariesLoader.h>
 #include <Dictionaries/DictionaryFactory.h>
+#include "config_core.h"
+
+#if USE_MYSQL
+#   include <mysqlxx/PoolFactory.h>
+#endif
 
 namespace DB
 {
@@ -24,4 +29,12 @@ ExternalLoader::LoadablePtr ExternalDictionariesLoader::create(
     bool dictionary_from_database = !repository_name.empty();
     return DictionaryFactory::instance().create(name, config, key_in_config, context, dictionary_from_database);
 }
+
+void ExternalDictionariesLoader::resetAll()
+{
+    #if USE_MYSQL
+        mysqlxx::PoolFactory::instance().reset();
+    #endif
+}
+
 }

dbms/src/Interpreters/ExternalDictionariesLoader.h

@@ -4,7 +4,6 @@
 #include <Interpreters/ExternalLoader.h>
 #include <memory>
 
-
 namespace DB
 {
 class Context;
@@ -29,6 +28,8 @@ public:
         return std::static_pointer_cast<const IDictionaryBase>(tryLoad(name));
     }
 
+    static void resetAll();
+
 protected:
     LoadablePtr create(const std::string & name, const Poco::Util::AbstractConfiguration & config,
             const std::string & key_in_config, const std::string & repository_name) const override;

dbms/src/Interpreters/InterpreterSystemQuery.cpp

@@ -216,6 +216,7 @@ BlockIO InterpreterSystemQuery::execute()
         case Type::RELOAD_DICTIONARY:
             context.checkAccess(AccessType::RELOAD_DICTIONARY);
             system_context.getExternalDictionariesLoader().loadOrReload(query.target_dictionary);
+            ExternalDictionariesLoader::resetAll();
             break;
         case Type::RELOAD_DICTIONARIES:
             context.checkAccess(AccessType::RELOAD_DICTIONARY);
@@ -223,6 +224,7 @@ BlockIO InterpreterSystemQuery::execute()
                     [&] () { system_context.getExternalDictionariesLoader().reloadAllTriedToLoad(); },
                     [&] () { system_context.getEmbeddedDictionaries().reload(); }
             );
+            ExternalDictionariesLoader::resetAll();
             break;
         case Type::RELOAD_EMBEDDED_DICTIONARIES:
             context.checkAccess(AccessType::RELOAD_DICTIONARY);

dbms/tests/integration/test_dictionaries_mysql/configs/config.xml

@@ -0,0 +1,30 @@
+<?xml version="1.0"?>
+<yandex>
+    <logger>
+        <level>trace</level>
+        <log>/var/log/clickhouse-server/clickhouse-server.log</log>
+        <errorlog>/var/log/clickhouse-server/clickhouse-server.err.log</errorlog>
+        <size>1000M</size>
+        <count>10</count>
+	</logger>
+
+    <tcp_port>9000</tcp_port>
+    <listen_host>127.0.0.1</listen_host>
+
+    <openSSL>
+        <client>
+            <cacheSessions>true</cacheSessions>
+            <verificationMode>none</verificationMode>
+            <invalidCertificateHandler>
+                <name>AcceptCertificateHandler</name>
+            </invalidCertificateHandler>
+        </client>
+    </openSSL>
+
+    <max_concurrent_queries>500</max_concurrent_queries>
+    <mark_cache_size>5368709120</mark_cache_size>
+    <path>./clickhouse/</path>
+    <users_config>users.xml</users_config>
+
+    <dictionaries_config>/etc/clickhouse-server/config.d/*.xml</dictionaries_config>
+</yandex>

dbms/tests/integration/test_dictionaries_mysql/configs/dictionaries/mysql_dict1.xml

@@ -0,0 +1,75 @@
+<?xml version="1.0"?>
+<yandex>
+   <dictionary>
+      <name>dict0</name>
+      <source>
+         <mysql >
+            <db>test</db>
+            <host>mysql1</host>
+            <port>3306</port>
+            <user>root</user>
+            <password>clickhouse</password>
+            <table>test0</table>
+            <close_connection>true</close_connection>
+            <share_connection>true</share_connection>
+         </mysql>
+      </source>
+      <layout>
+         <hashed/>
+      </layout>
+      <structure>
+         <id>
+            <name>id</name>
+            <type>UInt32</type>
+            <expression>CAST(id AS UNSIGNED)</expression>
+         </id>
+         <attribute>
+            <name>id</name>
+            <type>Int32</type>
+            <null_value></null_value>
+         </attribute>
+         <attribute>
+            <name>value</name>
+            <type>String</type>
+            <null_value>(UNDEFINED)</null_value>
+         </attribute>
+      </structure>
+      <lifetime>0</lifetime>
+  </dictionary>
+  <dictionary>
+      <name>dict1</name>
+      <source>
+         <mysql >
+            <db>test</db>
+            <host>mysql1</host>
+            <port>3306</port>
+            <user>root</user>
+            <password>clickhouse</password>
+            <table>test1</table>
+            <close_connection>true</close_connection>
+            <share_connection>true</share_connection>
+         </mysql>
+      </source>
+      <layout>
+         <hashed/>
+      </layout>
+      <structure>
+         <id>
+            <name>id</name>
+            <type>UInt32</type>
+            <expression>CAST(id AS UNSIGNED)</expression>
+         </id>
+         <attribute>
+            <name>id</name>
+            <type>Int32</type>
+            <null_value></null_value>
+         </attribute>
+         <attribute>
+            <name>value</name>
+            <type>String</type>
+            <null_value>(UNDEFINED)</null_value>
+         </attribute>
+      </structure>
+      <lifetime>0</lifetime>
+   </dictionary>
+</yandex>

dbms/tests/integration/test_dictionaries_mysql/configs/dictionaries/mysql_dict2.xml

@@ -0,0 +1,113 @@
+<?xml version="1.0"?>
+<yandex>
+      <dictionary>
+      <name>dict2</name>
+      <source>
+         <mysql >
+            <db>test</db>
+            <host>mysql1</host>
+            <port>3306</port>
+            <user>root</user>
+            <password>clickhouse</password>
+            <table>test2</table>
+            <close_connection>true</close_connection>
+            <share_connection>true</share_connection>
+         </mysql>
+      </source>
+      <layout>
+         <hashed/>
+      </layout>
+      <structure>
+         <id>
+            <name>id</name>
+            <type>UInt32</type>
+            <expression>CAST(id AS UNSIGNED)</expression>
+         </id>
+         <attribute>
+            <name>id</name>
+            <type>Int32</type>
+            <null_value></null_value>
+         </attribute>
+         <attribute>
+            <name>value</name>
+            <type>String</type>
+            <null_value>(UNDEFINED)</null_value>
+         </attribute>
+      </structure>
+      <lifetime>0</lifetime>
+   </dictionary>
+   
+   <dictionary>
+      <name>dict3</name>
+      <source>
+         <mysql >
+            <db>test</db>
+            <host>mysql1</host>
+            <port>3306</port>
+            <user>root</user>
+            <password>clickhouse</password>
+            <table>test3</table>
+            <close_connection>true</close_connection>
+            <share_connection>true</share_connection>
+         </mysql>
+      </source>
+      <layout>
+         <hashed/>
+      </layout>
+      <structure>
+         <id>
+            <name>id</name>
+            <type>UInt32</type>
+            <expression>CAST(id AS UNSIGNED)</expression>
+         </id>
+         <attribute>
+            <name>id</name>
+            <type>Int32</type>
+            <null_value></null_value>
+         </attribute>
+         <attribute>
+            <name>value</name>
+            <type>String</type>
+            <null_value>(UNDEFINED)</null_value>
+         </attribute>
+      </structure>
+      <lifetime>0</lifetime>
+   </dictionary>
+   <dictionary>
+      <name>dict4</name>
+      <source>
+         <mysql >
+            <db>test</db>
+            <host>mysql1</host>
+            <port>3306</port>
+            <user>root</user>
+            <password>clickhouse</password>
+            <table>test4</table>
+            <close_connection>true</close_connection>
+            <share_connection>true</share_connection>
+         </mysql>
+      </source>
+      <layout>
+         <hashed/>
+      </layout>
+      <structure>
+         <id>
+            <name>id</name>
+            <type>UInt32</type>
+            <expression>CAST(id AS UNSIGNED)</expression>
+         </id>
+         <attribute>
+            <name>id</name>
+            <type>Int32</type>
+            <null_value></null_value>
+         </attribute>
+         <attribute>
+            <name>value</name>
+            <type>String</type>
+            <null_value>(UNDEFINED)</null_value>
+         </attribute>
+      </structure>
+      <lifetime>0</lifetime>
+   </dictionary>
+   
+</yandex>

dbms/tests/integration/test_dictionaries_mysql/configs/remote_servers.xml

@@ -0,0 +1,12 @@
+<yandex>
+    <remote_servers>
+        <test_cluster>
+            <shard>
+                <replica>
+                    <host>instance</host>
+                    <port>9000</port>
+                </replica>
+            </shard>
+        </test_cluster>
+    </remote_servers>
+</yandex>

dbms/tests/integration/test_dictionaries_mysql/configs/users.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0"?>
+<yandex>
+    <profiles>
+        <default>
+        </default>
+    </profiles>
+
+    <users>
+        <default>
+            <password></password>
+            <networks incl="networks" replace="replace">
+                <ip>::/0</ip>
+            </networks>
+            <profile>default</profile>
+            <quota>default</quota>
+        </default>
+    </users>
+
+    <quotas>
+        <default>
+        </default>
+    </quotas>
+</yandex>

dbms/tests/integration/test_dictionaries_mysql/test.py

@@ -0,0 +1,95 @@
+import pytest
+import os
+import time
+
+## sudo -H pip install PyMySQL
+import pymysql.cursors
+
+from helpers.cluster import ClickHouseCluster
+from helpers.test_tools import assert_eq_with_retry
+
+SCRIPT_DIR = os.path.dirname(os.path.realpath(__file__))
+CONFIG_FILES = ['configs/dictionaries/mysql_dict1.xml', 'configs/dictionaries/mysql_dict2.xml', 'configs/remote_servers.xml']
+
+cluster = ClickHouseCluster(__file__, base_configs_dir=os.path.join(SCRIPT_DIR, 'configs'))
+instance = cluster.add_instance('instance', main_configs=CONFIG_FILES, with_mysql = True)
+
+create_table_mysql_template = """
+    CREATE TABLE IF NOT EXISTS `test`.`{}` (
+        `id` int(11) NOT NULL,
+        `value` varchar(50) NOT NULL,
+        PRIMARY KEY (`id`)
+    ) ENGINE=InnoDB;
+    """
+
+create_clickhouse_dictionary_table_template = """
+    CREATE TABLE IF NOT EXISTS `test`.`dict_table_{}` (`id` Int32, `value` String) ENGINE = Dictionary({})
+    """
+
+@pytest.fixture(scope="module")
+def started_cluster():
+    try:
+        #time.sleep(30)
+        cluster.start()
+        
+        # Create a MySQL database
+        mysql_connection = get_mysql_conn()
+        create_mysql_db(mysql_connection, 'test')
+        mysql_connection.close()
+        
+        # Create database in ClickHouse
+        instance.query("CREATE DATABASE IF NOT EXISTS test")
+    
+        # Create database in ClickChouse using MySQL protocol (will be used for data insertion)
+        instance.query("CREATE DATABASE clickhouse_mysql ENGINE = MySQL('mysql1:3306', 'test', 'root', 'clickhouse')")
+        
+        yield cluster
+
+    finally:
+        cluster.shutdown()
+
+
+def test_load_mysql_dictionaries(started_cluster):
+    # Load dictionaries
+    query = instance.query
+    query("SYSTEM RELOAD DICTIONARIES")
+    
+    for n in range(0, 5):
+        # Create MySQL tables, fill them and create CH dict tables
+        prepare_mysql_table('test', str(n))
+    
+    # Check dictionaries are loaded and have correct number of elements
+    for n in range(0, 100):
+        # Force reload of dictionaries (each 10 iteration)
+        if (n % 10) == 0:
+            query("SYSTEM RELOAD DICTIONARIES")
+
+        # Check number of row
+        assert query("SELECT count() FROM `test`.`dict_table_{}`".format('test' + str(n % 5))).rstrip() == '10000'
+
+def create_mysql_db(mysql_connection, name):
+    with mysql_connection.cursor() as cursor:
+        cursor.execute("CREATE DATABASE IF NOT EXISTS {} DEFAULT CHARACTER SET 'utf8'".format(name))
+
+def prepare_mysql_table(table_name, index):
+    mysql_connection = get_mysql_conn()
+    
+    # Create table
+    create_mysql_table(mysql_connection, table_name + str(index))
+
+    # Insert rows using CH
+    query = instance.query
+    query("INSERT INTO `clickhouse_mysql`.{}(id, value) select number, concat('{} value ', toString(number)) from numbers(10000) ".format(table_name + str(index), table_name + str(index)))
+    assert query("SELECT count() FROM `clickhouse_mysql`.{}".format(table_name + str(index))).rstrip() == '10000'
+    mysql_connection.close()
+    
+    #Create CH Dictionary tables based on MySQL tables 
+    query(create_clickhouse_dictionary_table_template.format(table_name + str(index), 'dict' + str(index)))
+
+def get_mysql_conn():
+    conn = pymysql.connect(user='root', password='clickhouse', host='127.0.0.10', port=3308)
+    return conn
+
+def create_mysql_table(conn, table_name):
+    with conn.cursor() as cursor:
+        cursor.execute(create_table_mysql_template.format(table_name))