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// grid.h
/**
* 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 <boost/date_time/posix_time/posix_time.hpp>
#include "../util/time_support.h"
#include "../util/concurrency/mutex.h"
#include "config.h" // DBConfigPtr
namespace mongo {
/**
* stores meta-information about the grid
* TODO: used shard_ptr for DBConfig pointers
*/
class Grid {
public:
Grid() : _lock( "Grid" ) , _allowLocalShard( true ) { }
/**
* gets the config the db.
* will return an empty DBConfig if not in db already
*/
DBConfigPtr getDBConfig( const StringData& ns , bool create=true , const string& shardNameHint="" );
/**
* removes db entry.
* on next getDBConfig call will fetch from db
*/
void removeDB( const std::string& db );
/**
* removes db entry - only this DBConfig object will be removed,
* other DBConfigs which may have been created in the meantime will not be harmed
* on next getDBConfig call will fetch from db
*
* Using this method avoids race conditions where multiple threads detect a database
* reload has failed.
*
* Example : N threads receive version exceptions and dbConfig.reload(), while
* simultaneously a dropDatabase is occurring. In the meantime, the dropDatabase call
* attempts to create a DBConfig object if one does not exist, to load the db info,
* but the config is repeatedly deleted as soon as it is created. Using this method
* prevents the deletion of configs we don't know about.
*
*/
void removeDBIfExists( const DBConfig& database );
/**
* @return true if shards and config servers are allowed to use 'localhost' in address
*/
bool allowLocalHost() const;
/**
* @param whether to allow shards and config servers to use 'localhost' in address
*/
void setAllowLocalHost( bool allow );
/**
*
* addShard will create a new shard in the grid. It expects a mongod process to be running
* on the provided address. Adding a shard that is a replica set is supported.
*
* @param name is an optional string with the name of the shard. if omitted, grid will
* generate one and update the parameter.
* @param servers is the connection string of the shard being added
* @param maxSize is the optional space quota in bytes. Zeros means there's no limitation to
* space usage
* @param errMsg is the error description in case the operation failed.
* @return true if shard was successfully added.
*/
bool addShard( string* name , const ConnectionString& servers , long long maxSize , string& errMsg );
/**
* @return true if the config database knows about a host 'name'
*/
bool knowAboutShard( const string& name ) const;
/**
* @return true if the chunk balancing functionality is enabled
*/
bool shouldBalance( const string& ns = "", BSONObj* balancerDocOut = 0 ) const;
/**
*
* Obtain grid configuration and settings data.
*
* @param name identifies a particular type of configuration data.
* @return a BSON object containing the requested data.
*/
BSONObj getConfigSetting( const std::string& name ) const;
unsigned long long getNextOpTime() const;
void flushConfig();
// exposed methods below are for testing only
/**
* @param balancerDoc bson that may contain a window of time for the balancer to work
* format { ... , activeWindow: { start: "8:30" , stop: "19:00" } , ... }
* @return true if there is no window of time specified for the balancer or it we're currently in it
*/
static bool _inBalancingWindow( const BSONObj& balancerDoc , const boost::posix_time::ptime& now );
private:
mongo::mutex _lock; // protects _databases; TODO: change to r/w lock ??
map<string, DBConfigPtr > _databases; // maps ns to DBConfig's
bool _allowLocalShard; // can 'localhost' be used in shard addresses?
/**
* @param name is the chose name for the shard. Parameter is mandatory.
* @return true if it managed to generate a shard name. May return false if (currently)
* 10000 shard
*/
bool _getNewShardName( string* name ) const;
/**
* @return whether a give dbname is used for shard "local" databases (e.g., admin or local)
*/
static bool _isSpecialLocalDB( const string& dbName );
/**
* @param balancerDoc bson that may contain a marker to stop the balancer
* format { ... , stopped: [ "true" | "false" ] , ... }
* @return true if the marker is present and is set to true
*/
static bool _balancerStopped( const BSONObj& balancerDoc );
};
extern Grid grid;
} // namespace mongo
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