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// @file
/*
* Copyright (C) 2010 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 <map>
#include "../../client/dbclient.h"
namespace mongo {
/** here we keep a single connection (with reconnect) for a set of hosts,
one each, and allow one user at a time per host. if in use already for that
host, we block. so this is an easy way to keep a 1-deep pool of connections
that many threads can share.
thread-safe.
Example:
{
ScopedConn c("foo.acme.com:9999");
c->runCommand(...);
}
throws exception on connect error (but fine to try again later with a new
scopedconn object for same host).
*/
class ScopedConn {
public:
/** throws assertions if connect failure etc. */
ScopedConn(string hostport);
~ScopedConn();
/* If we were to run a query and not exhaust the cursor, future use of the connection would be problematic.
So here what we do is wrapper known safe methods and not allow cursor-style queries at all. This makes
ScopedConn limited in functionality but very safe. More non-cursor wrappers can be added here if needed.
*/
bool runCommand(const string &dbname, const BSONObj& cmd, BSONObj &info, int options=0) {
return conn()->runCommand(dbname, cmd, info, options);
}
unsigned long long count(const string &ns) {
return conn()->count(ns);
}
BSONObj findOne(const string &ns, const Query& q, const BSONObj *fieldsToReturn = 0, int queryOptions = 0) {
return conn()->findOne(ns, q, fieldsToReturn, queryOptions);
}
private:
auto_ptr<scoped_lock> connLock;
static mutex mapMutex;
struct X {
mutex z;
DBClientConnection cc;
X() : z("X"), cc(/*reconnect*/true, 0, /*timeout*/10) {
cc._logLevel = 2;
}
} *x;
typedef map<string,ScopedConn::X*> M;
static M& _map;
DBClientConnection* conn() { return &x->cc; }
};
inline ScopedConn::ScopedConn(string hostport) {
bool first = false;
{
scoped_lock lk(mapMutex);
x = _map[hostport];
if( x == 0 ) {
x = _map[hostport] = new X();
first = true;
connLock.reset( new scoped_lock(x->z) );
}
}
if( !first ) {
connLock.reset( new scoped_lock(x->z) );
return;
}
// we already locked above...
string err;
x->cc.connect(hostport, err);
}
inline ScopedConn::~ScopedConn() {
// conLock releases...
}
/*inline DBClientConnection* ScopedConn::operator->() {
return &x->cc;
}*/
}
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