ClickHouse/libs/libmysqlxx/include/mysqlxx/Pool.h

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#pragma once
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#include <list>
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#include <memory>
#include <mutex>
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#include <Poco/Exception.h>
#include <mysqlxx/Connection.h>
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#define MYSQLXX_POOL_DEFAULT_START_CONNECTIONS 1
#define MYSQLXX_POOL_DEFAULT_MAX_CONNECTIONS 16
#define MYSQLXX_POOL_SLEEP_ON_CONNECT_FAIL 1
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namespace mysqlxx
{
/** MySQL connections pool.
* This class is poorly connected with mysqlxx and is made in different style (was taken from old code).
* Usage:
* mysqlxx::Pool pool("mysql_params");
*
* void thread()
* {
* mysqlxx::Pool::Entry connection = pool.Get();
* std::string s = connection->query("SELECT 'Hello, world!' AS world").use().fetch()["world"].getString();
* }
* TODO: simplify with PoolBase.
*/
class Pool final
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{
protected:
/// Information about connection.
struct Connection
{
mysqlxx::Connection conn;
int ref_count = 0;
};
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public:
/// Connection with database.
class Entry
{
public:
Entry() {}
Entry(const Entry & src)
: data(src.data), pool(src.pool)
{
incrementRefCount();
}
~Entry()
{
decrementRefCount();
}
Entry & operator= (const Entry & src)
{
pool = src.pool;
if (data)
decrementRefCount();
data = src.data;
if (data)
incrementRefCount();
return * this;
}
bool isNull() const
{
return data == nullptr;
}
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operator mysqlxx::Connection & () &
{
forceConnected();
return data->conn;
}
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operator const mysqlxx::Connection & () const &
{
forceConnected();
return data->conn;
}
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const mysqlxx::Connection * operator->() const &
{
forceConnected();
return &data->conn;
}
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mysqlxx::Connection * operator->() &
{
forceConnected();
return &data->conn;
}
Entry(Pool::Connection * conn, Pool * p)
: data(conn), pool(p)
{
incrementRefCount();
}
std::string getDescription() const
{
if (pool)
return pool->getDescription();
else
return "pool is null";
}
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void disconnect();
friend class Pool;
private:
/// Pointer to mysqlxx connection.
Connection * data = nullptr;
/// Pointer to pool we are belonging to.
Pool * pool = nullptr;
/// Connects to database. If connection is failed then waits and repeats again.
void forceConnected() const;
/// Connects to database. If connection is failed then returns false.
bool tryForceConnected() const
{
return data->conn.ping();
}
void incrementRefCount();
void decrementRefCount();
};
Pool(const std::string & config_name,
unsigned default_connections_ = MYSQLXX_POOL_DEFAULT_START_CONNECTIONS,
unsigned max_connections_ = MYSQLXX_POOL_DEFAULT_MAX_CONNECTIONS,
const char * parent_config_name_ = nullptr)
: Pool{Poco::Util::Application::instance().config(), config_name,
default_connections_, max_connections_, parent_config_name_}
{}
/**
* @param config_name Setting name in configuration file
* @param default_connections_ Number of default connections
* @param max_connections_ Maximum number of connections
*/
Pool(const Poco::Util::AbstractConfiguration & cfg, const std::string & config_name,
unsigned default_connections_ = MYSQLXX_POOL_DEFAULT_START_CONNECTIONS,
unsigned max_connections_ = MYSQLXX_POOL_DEFAULT_MAX_CONNECTIONS,
const char * parent_config_name_ = nullptr);
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/** Like with mysqlxx::Connection, either port either socket should be specified.
* If server is localhost and socket is not empty, than socket is used. Otherwise, server and port is used.
*/
Pool(const std::string & db_,
const std::string & server_,
const std::string & user_ = "",
const std::string & password_ = "",
unsigned port_ = 0,
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const std::string & socket_ = "",
unsigned connect_timeout_ = MYSQLXX_DEFAULT_TIMEOUT,
unsigned rw_timeout_ = MYSQLXX_DEFAULT_RW_TIMEOUT,
unsigned default_connections_ = MYSQLXX_POOL_DEFAULT_START_CONNECTIONS,
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unsigned max_connections_ = MYSQLXX_POOL_DEFAULT_MAX_CONNECTIONS,
unsigned enable_local_infile_ = MYSQLXX_DEFAULT_ENABLE_LOCAL_INFILE)
: default_connections(default_connections_), max_connections(max_connections_),
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db(db_), server(server_), user(user_), password(password_), port(port_), socket(socket_),
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connect_timeout(connect_timeout_), rw_timeout(rw_timeout_), enable_local_infile(enable_local_infile_) {}
Pool(const Pool & other)
: default_connections{other.default_connections},
max_connections{other.max_connections},
db{other.db}, server{other.server},
user{other.user}, password{other.password},
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port{other.port}, socket{other.socket},
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connect_timeout{other.connect_timeout}, rw_timeout{other.rw_timeout},
enable_local_infile{other.enable_local_infile}
{}
Pool & operator=(const Pool &) = delete;
~Pool();
/// Allocates connection.
Entry Get();
/// Allocates connection.
/// If database is not accessible, returns empty Entry object.
/// If pool is overflowed, throws exception.
Entry tryGet();
/// Get description of database.
std::string getDescription() const
{
return description;
}
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protected:
/// Number of MySQL connections which are created at launch.
unsigned default_connections;
/// Maximum possible number of connections
unsigned max_connections;
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private:
/// Initialization flag.
bool initialized{false};
/// List of connections.
using Connections = std::list<Connection *>;
/// List of connections.
Connections connections;
/// Lock for connections list access
std::mutex mutex;
/// Description of connection.
std::string description;
/// Connection settings.
std::string db;
std::string server;
std::string user;
std::string password;
unsigned port;
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std::string socket;
unsigned connect_timeout;
unsigned rw_timeout;
std::string ssl_ca;
std::string ssl_cert;
std::string ssl_key;
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bool enable_local_infile;
/// True if connection was established at least once.
bool was_successful{false};
/// Initialises class if it wasn't.
void initialize();
/** Create new connection. */
Connection * allocConnection(bool dont_throw_if_failed_first_time = false);
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};
}