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/* connpool.h */
/**
* Copyright (C) 2008 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include <queue>
#include "dbclient.h"
struct PoolForHost {
queue<DBClientConnection*> pool;
};
class DBConnectionPool {
boost::mutex poolMutex;
map<string,PoolForHost*> pools;
public:
/* generally, use ScopedDbConnection and do not call these directly */
DBClientConnection *get(const string& host);
void release(const string& host, DBClientConnection *c) {
boostlock L(poolMutex);
pools[host]->pool.push(c);
}
};
extern DBConnectionPool pool;
/* Use to get a connection from the pool. On exceptions things
clean up nicely.
*/
class ScopedDbConnection {
const string host;
DBClientConnection *_conn;
public:
DBClientConnection& conn() {
return *_conn;
}
/* throws UserAssertionAcception if can't connect */
ScopedDbConnection(const string& _host) :
host(_host), _conn( pool.get(_host) ) { }
/* Force closure of the connection. You should call this if you leave it in
a bad state. Destructor will do this too, but it is verbose.
*/
void kill() {
delete _conn;
_conn = 0;
}
/* Call this when you are done with the ocnnection.
Why? See note in the destructor below.
*/
void done() {
if ( _conn->isFailed() )
kill();
else
pool.release(host, _conn);
_conn = 0;
}
~ScopedDbConnection() {
if ( _conn ) {
/* you are supposed to call done(). if you did that, correctly, we
only get here if an exception was thrown. in such a scenario, we can't
be sure we fully read all expected data of a reply on the socket. so
we don't try to reuse the connection. The cout is just informational.
*/
cout << "~ScopedDBConnection: _conn != null\n";
kill();
}
}
};
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