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ReplicationFeatures/ParallelSlave

Contents 1 Parallel execution of row-based replication events on slave 2 Provides 3 Use case: 4 Limitations: 5 User interface: 6 References 7 Downloads 8 Thanks:

[edit] Parallel execution of row-based replication events on slave

[edit] Provides

Increases throughput of replication in terms of transactions per second. Reduces replication latency.

[edit] Use case:

Currently, replication does not scale well on multi-core machines. The single slave thread execute replication events one by one and have sometimes problems with a load produced on the master by concurrent multiple client connections. MySQL Cluster Replication benefits from parallelization as well because workload on the master side is generated by multiple machines.

[edit] Limitations:

Limitations that will be removed in later versions:

• May crash
• Tables must have primary key of an integer type
• Only parallel execution for INSERTs and DELETEs, not for UPDATEs. (No support for Update_rows event)
• If slave crashes during commit, then only part of a transaction can have been committed.

Limitations that will not be removed soon:

• Only works with transactional storage engines
• Only works with row-based events
• All transactions on slave should use SERIALIZABLE isolation level

[edit] User interface:

• The server configuration parameter

   --slave_parallel_workers=..., zero by default

• SHOW PROCESSLIST displays all engaged workers
• Parallel mode is not active by default, to set it invoke

   set @@global.slave_exec_mode='strict,parallel';

[edit] References

• WL#4648 Multi-threaded slave for row-based replication

[edit] Downloads

• Pre-release 0.1
  • Linux
    • mysql-5.1-parallel_slave-linux-i686.tar.gz

[edit] Thanks:

MySQL Replication and MySQL Cluster Team, including Mats, Lars, Andrei, Tomas, Jonas, Mikael.