In this blog, we’ll discuss how the Percona XtraDB Cluster threading model works.

Percona XtraDB Cluster (PXC) creates a different set of threads to service its operations. These threads are in addition to existing MySQL threads. Let’s understand what these threads are and how they’re used. There are three main groups of threads:

1. Applier thread(s)
   1. Applier threads are meant to apply write-sets that the node receives from other nodes (through cluster). (write-message is directed through

      gcv_recv_thread

      .)
   2. The number of applier threads is controlled using the

      wsrep_slave_thread

       configuration. (The default value is 1, so at least one wsrep applier thread …