diff options
Diffstat (limited to 'src/mongo/s/balance.h')
| -rw-r--r-- | src/mongo/s/balance.h | 155 |
1 files changed, 78 insertions, 77 deletions
diff --git a/src/mongo/s/balance.h b/src/mongo/s/balance.h index 1b7bd55aa29..c62e05c18f4 100644 --- a/src/mongo/s/balance.h +++ b/src/mongo/s/balance.h @@ -35,85 +35,86 @@ namespace mongo { - class BalancerPolicy; - struct MigrateInfo; - struct WriteConcernOptions; +class BalancerPolicy; +struct MigrateInfo; +struct WriteConcernOptions; + +/** + * The balancer is a background task that tries to keep the number of chunks across all + * servers of the cluster even. Although every mongos will have one balancer running, only one + * of them will be active at the any given point in time. The balancer uses a distributed lock + * for that coordination. + * + * The balancer does act continuously but in "rounds". At a given round, it would decide if + * there is an imbalance by checking the difference in chunks between the most and least + * loaded shards. It would issue a request for a chunk migration per round, if it found so. + */ +class Balancer : public BackgroundJob { +public: + Balancer(); + virtual ~Balancer(); + + // BackgroundJob methods + + virtual void run(); + + virtual std::string name() const { + return "Balancer"; + } + +private: + // hostname:port of my mongos + std::string _myid; + + // time the Balancer started running + time_t _started; + + // number of moved chunks in last round + int _balancedLastTime; + + // decide which chunks to move; owned here. + std::unique_ptr<BalancerPolicy> _policy; /** - * The balancer is a background task that tries to keep the number of chunks across all - * servers of the cluster even. Although every mongos will have one balancer running, only one - * of them will be active at the any given point in time. The balancer uses a distributed lock - * for that coordination. + * Checks that the balancer can connect to all servers it needs to do its job. + * + * @return true if balancing can be started * - * The balancer does act continuously but in "rounds". At a given round, it would decide if - * there is an imbalance by checking the difference in chunks between the most and least - * loaded shards. It would issue a request for a chunk migration per round, if it found so. + * This method throws on a network exception */ - class Balancer : public BackgroundJob { - public: - Balancer(); - virtual ~Balancer(); - - // BackgroundJob methods - - virtual void run(); - - virtual std::string name() const { return "Balancer"; } - - private: - // hostname:port of my mongos - std::string _myid; - - // time the Balancer started running - time_t _started; - - // number of moved chunks in last round - int _balancedLastTime; - - // decide which chunks to move; owned here. - std::unique_ptr<BalancerPolicy> _policy; - - /** - * Checks that the balancer can connect to all servers it needs to do its job. - * - * @return true if balancing can be started - * - * This method throws on a network exception - */ - bool _init(); - - /** - * Gathers all the necessary information about shards and chunks, and decides whether there are candidate chunks to - * be moved. - * - * @param conn is the connection with the config server(s) - * @param candidateChunks (IN/OUT) filled with candidate chunks, one per collection, that could possibly be moved - */ - void _doBalanceRound(std::vector<std::shared_ptr<MigrateInfo>>* candidateChunks); - - /** - * Issues chunk migration request, one at a time. - * - * @param candidateChunks possible chunks to move - * @param writeConcern detailed write concern. NULL means the default write concern. - * @param waitForDelete wait for deletes to complete after each chunk move - * @return number of chunks effectively moved - */ - int _moveChunks(const std::vector<std::shared_ptr<MigrateInfo>>& candidateChunks, - const WriteConcernOptions* writeConcern, - bool waitForDelete); - - /** - * Marks this balancer as being live on the config server(s). - */ - void _ping( bool waiting = false ); - - /** - * @return true if all the servers listed in configdb as being shards are reachable and are distinct processes - */ - bool _checkOIDs(); - - }; - - extern Balancer balancer; + bool _init(); + + /** + * Gathers all the necessary information about shards and chunks, and decides whether there are candidate chunks to + * be moved. + * + * @param conn is the connection with the config server(s) + * @param candidateChunks (IN/OUT) filled with candidate chunks, one per collection, that could possibly be moved + */ + void _doBalanceRound(std::vector<std::shared_ptr<MigrateInfo>>* candidateChunks); + + /** + * Issues chunk migration request, one at a time. + * + * @param candidateChunks possible chunks to move + * @param writeConcern detailed write concern. NULL means the default write concern. + * @param waitForDelete wait for deletes to complete after each chunk move + * @return number of chunks effectively moved + */ + int _moveChunks(const std::vector<std::shared_ptr<MigrateInfo>>& candidateChunks, + const WriteConcernOptions* writeConcern, + bool waitForDelete); + + /** + * Marks this balancer as being live on the config server(s). + */ + void _ping(bool waiting = false); + + /** + * @return true if all the servers listed in configdb as being shards are reachable and are distinct processes + */ + bool _checkOIDs(); +}; + +extern Balancer balancer; } |