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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <list>
#include <map>
#include "mongo/client/dbclient_connection.h"
#include "mongo/stdx/mutex.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/util/net/hostandport.h"
#include "mongo/util/time_support.h"
namespace mongo {
namespace executor {
class NetworkConnectionHook;
} // namespace executor
/**
* Represents a pool of connections to a MongoDB server. The pool is synchronized internally
* and its methods can be called from multiple threads, however once a connection is obtained
* it should only be used from one thread in accordance with the rules of DBClientBase.
*/
class ConnectionPool {
ConnectionPool(const ConnectionPool&) = delete;
ConnectionPool& operator=(const ConnectionPool&) = delete;
public:
/**
* Information about a connection in the pool.
*/
struct ConnectionInfo {
ConnectionInfo(DBClientConnection* theConn, Date_t date)
: conn(theConn), creationDate(date) {}
// A connection in the pool.
DBClientConnection* const conn;
// The date at which the connection was created.
const Date_t creationDate;
};
typedef std::list<ConnectionInfo> ConnectionList;
typedef stdx::unordered_map<HostAndPort, ConnectionList> HostConnectionMap;
typedef std::map<HostAndPort, Date_t> HostLastUsedMap;
/**
* RAII class for connections from the pool. To use the connection pool, instantiate one of
* these with a pointer to the pool, the identity of the target node and the timeout for
* network operations, use it like a pointer to a connection, and then call done() on
* successful completion. Failure to call done() will lead to the connection being reaped
* when the holder goes out of scope.
*/
class ConnectionPtr {
ConnectionPtr(const ConnectionPtr&) = delete;
ConnectionPtr& operator=(const ConnectionPtr&) = delete;
public:
/**
* Constructs a ConnectionPtr referring to a connection to "target" drawn from "pool",
* with the network timeout set to "timeout".
*
* Throws DBExceptions if the connection cannot be established.
*/
ConnectionPtr(ConnectionPool* pool,
const HostAndPort& target,
Date_t now,
Milliseconds timeout);
/**
* Destructor reaps the connection if it wasn't already returned to the pool by calling
* done().
*/
~ConnectionPtr();
// We need to provide user defined move operations as we need to set the pool
// pointer to nullptr on the moved-from object.
ConnectionPtr(ConnectionPtr&&);
ConnectionPtr& operator=(ConnectionPtr&&);
/**
* Obtains the underlying connection which can be used for making calls to the server.
*/
DBClientConnection* get() const {
return _connInfo->conn;
}
/**
* Releases the connection back to the pool from which it was drawn.
*/
void done(Date_t now);
private:
ConnectionPool* _pool;
ConnectionList::iterator _connInfo;
};
/**
* Instantiates a new connection pool with the specified tags to be applied to the
* messaging ports that it opens.
*
* @param messagingPortTags tags to be applied to the messaging ports for each of the
* connections. If no tags are required, use 0.
*/
ConnectionPool(int messagingPortTags, std::unique_ptr<executor::NetworkConnectionHook> hook);
ConnectionPool(int messagingPortTags);
~ConnectionPool();
/**
* Acquires a connection to "target" with the given "timeout", or throws a DBException.
* Intended for use by ConnectionPtr.
*/
ConnectionList::iterator acquireConnection(const HostAndPort& target,
Date_t now,
Milliseconds timeout);
/**
* Releases a connection back into the pool.
* Intended for use by ConnectionPtr.
* Call this for connections that can safely be reused.
*/
void releaseConnection(ConnectionList::iterator iter, Date_t now);
/**
* Destroys a connection previously acquired from the pool.
* Intended for use by ConnectionPtr.
* Call this for connections that cannot be reused.
*/
void destroyConnection(ConnectionList::iterator);
/**
* Closes all connections currently in use, to ensure that the network threads
* terminate promptly during shutdown.
*/
void closeAllInUseConnections();
/**
* Reaps all connections in the pool that are too old as of "now".
*/
void cleanUpOlderThan(Date_t now);
private:
/**
* Returns true if the given connection is young enough to keep in the pool.
*/
static bool _shouldKeepConnection(Date_t now, const ConnectionInfo& connInfo);
/**
* Apply cleanup policy to any host(s) not active in the last kCleanupInterval milliseconds.
*/
void _cleanUpStaleHosts_inlock(Date_t now);
/**
* Reaps connections in "hostConns" that are too old or have been in the pool too long as of
* "now". Expects _mutex to be held.
*/
void _cleanUpOlderThan_inlock(Date_t now, ConnectionList* hostConns);
/**
* Destroys the connection associated with "iter" and removes "iter" fron connList.
*/
static void _destroyConnection_inlock(ConnectionList* connList, ConnectionList::iterator iter);
// Flags to apply to the opened connections
const int _messagingPortTags;
// Mutex guarding members of the connection pool
stdx::mutex _mutex;
// Map from HostAndPort to idle connections.
HostConnectionMap _connections;
// List of non-idle connections.
ConnectionList _inUseConnections;
// Map of HostAndPorts to when they were last used.
HostLastUsedMap _lastUsedHosts;
// Time representing when the connections were last cleaned.
Date_t _lastCleanUpTime;
// The connection hook for this pool. May be nullptr if there is no hook.
const std::unique_ptr<executor::NetworkConnectionHook> _hook;
};
} // namespace mongo
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