MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0

19.2.3 Replication Threads

MySQL replication capabilities are implemented using the following types of threads:

You can enable further parallelization for tasks on a replica by setting the system variable replica_parallel_workers (MySQL 8.0.26 or later) or slave_parallel_workers (prior to MySQL 8.0.26) to a value greater than 0. When this is done, the replica creates the specified number of worker threads to apply transactions, plus a coordinator thread which reads transactions from the relay log and assigns them to workers. A replica with replica_parallel_workers (slave_parallel_workers) set to a value greater than 0 is called a multithreaded replica. If you are using multiple replication channels, each channel has the number of threads specified using this variable.


Multithreaded replicas are supported by NDB Cluster beginning with NDB 8.0.33. (Previously, NDB silently ignored any setting for replica_parallel_workers.) See Section 25.7.11, “NDB Cluster Replication Using the Multithreaded Applier”, for more information.