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/**
* Copyright (C) 2014 MongoDB 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/>.
*
* 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 GNU Affero General 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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kSharding
#include "mongo/platform/basic.h"
#include "mongo/s/client/scc_fast_query_handler.h"
#include <vector>
#include "mongo/base/init.h"
#include "mongo/bson/util/builder.h"
#include "mongo/client/connpool.h"
#include "mongo/client/dbclientcursor.h"
#include "mongo/client/dbclientinterface.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/server_parameters.h"
#include "mongo/util/log.h"
namespace mongo {
using std::unique_ptr;
using std::endl;
using std::string;
using std::vector;
/**
* This parameter turns on fastest config reads for auth data only - *.system.users collections
* and the "usersInfo" command. This should be enough to prevent a non-responsive config from
* hanging other operations in a cluster.
*/
MONGO_EXPORT_SERVER_PARAMETER(internalSCCAllowFastestAuthConfigReads, bool, false);
/**
* TESTING ONLY.
*
* This parameter turns on fastest config reads for *all* config.* collections except those
* deemed extremely critical (config.version, config.locks).
*
* NOT FOR PRODUCTION USE.
*/
MONGO_EXPORT_SERVER_PARAMETER(internalSCCAllowFastestMetadataConfigReads, bool, false);
//
// The shared environment for MultiHostQueries
//
namespace {
class MultiQueryEnv : public MultiHostQueryOp::SystemEnv {
public:
virtual ~MultiQueryEnv() {}
Date_t currentTimeMillis();
StatusWith<DBClientCursor*> doBlockingQuery(const ConnectionString& host,
const QuerySpec& query);
};
StatusWith<DBClientCursor*> MultiQueryEnv::doBlockingQuery(const ConnectionString& host,
const QuerySpec& query) {
//
// Note that this function may be active during shutdown. This means that we must
// handle connection pool shutdown exceptions (uasserts). The results of this
// operation must then be correctly discarded by the calling thread.
//
unique_ptr<DBClientCursor> cursor;
try {
ScopedDbConnection conn(host, 30.0 /* timeout secs */);
cursor = conn->query(query.ns(),
query.filter(),
query.ntoreturn(),
query.ntoskip(),
query.fieldsPtr(),
query.options(),
0);
if (NULL == cursor.get()) {
// Confusingly, exceptions here are written to the log, not thrown
StringBuilder builder;
builder << "error querying server " << host.toString()
<< ", could not create cursor for query";
warning() << builder.str() << endl;
return StatusWith<DBClientCursor*>(ErrorCodes::HostUnreachable, builder.str());
}
// Confusingly, this *detaches* the cursor from the connection it was established
// on, further getMore calls will use a (potentially different) ScopedDbConnection.
//
// Calls done() too.
cursor->attach(&conn);
} catch (const DBException& ex) {
return StatusWith<DBClientCursor*>(ex.toStatus());
}
return StatusWith<DBClientCursor*>(cursor.release());
}
Date_t MultiQueryEnv::currentTimeMillis() {
return jsTime();
}
}
// Shared networking environment which executes queries.
// NOTE: This environment must stay in scope as long as per-host threads are executing queries -
// i.e. for the lifetime of the server.
// Once the thread pools are disposed and connections shut down, the per-host threads should
// be self-contained and correctly shut down after discarding the results.
static MultiQueryEnv* _multiQueryEnv;
namespace {
//
// Create the shared multi-query environment at startup
//
MONGO_INITIALIZER(InitMultiQueryEnv)(InitializerContext* context) {
// Leaked intentionally
_multiQueryEnv = new MultiQueryEnv();
return Status::OK();
}
}
//
// Per-SCC handling of queries
//
SCCFastQueryHandler::SCCFastQueryHandler() : _queryThreads(1, false) {}
bool SCCFastQueryHandler::canHandleQuery(const string& ns, Query query) {
if (!internalSCCAllowFastestAuthConfigReads && !internalSCCAllowFastestMetadataConfigReads) {
return false;
}
//
// More operations can be added here
//
// NOTE: Not all operations actually pass through the SCC _queryOnActive path - notable
// exceptions include anything related to direct query ops and direct operations for
// connection maintenance.
//
NamespaceString nss(ns);
if (nss.isCommand()) {
BSONObj cmdObj = query.getFilter();
string cmdName = cmdObj.firstElement().fieldName();
if (cmdName == "usersInfo")
return true;
} else if (nss.coll() == "system.users") {
return true;
}
//
// Allow fastest config reads for all collections except for those involved in locks and
// cluster versioning.
//
if (!internalSCCAllowFastestMetadataConfigReads)
return false;
if (nss.db() != "config")
return false;
if (nss.coll() != "version" && nss.coll() != "locks" && nss.coll() != "lockpings") {
return true;
}
return false;
}
static vector<ConnectionString> getHosts(const vector<string> hostStrings) {
vector<ConnectionString> hosts;
for (vector<string>::const_iterator it = hostStrings.begin(); it != hostStrings.end(); ++it) {
string errMsg;
ConnectionString host;
hosts.push_back(ConnectionString::parse(*it, errMsg));
invariant(hosts.back().type() != ConnectionString::INVALID);
}
return hosts;
}
unique_ptr<DBClientCursor> SCCFastQueryHandler::handleQuery(const vector<string>& hostStrings,
const string& ns,
Query query,
int nToReturn,
int nToSkip,
const BSONObj* fieldsToReturn,
int queryOptions,
int batchSize) {
MultiHostQueryOp queryOp(_multiQueryEnv, &_queryThreads);
QuerySpec querySpec(ns,
query.obj,
fieldsToReturn ? *fieldsToReturn : BSONObj(),
nToSkip,
nToReturn,
queryOptions);
// TODO: Timeout must be passed down here as well - 30s timeout may not be applicable for
// all operations handled.
StatusWith<DBClientCursor*> status =
queryOp.queryAny(getHosts(hostStrings), querySpec, 30 * 1000);
uassertStatusOK(status.getStatus());
unique_ptr<DBClientCursor> cursor(status.getValue());
return cursor;
}
}
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