Monitoring flow control in a Galera cluster is very important. If
you do not, you will not understand why writes may sometimes be
stalled. Percona XtraDB Cluster 5.6 provides 2 status
variables for such monitoring:
wsrep_flow_control_paused_ns. Which one should you
What is flow control?
Flow control does not exist with regular MySQL replication, but only with Galera replication. It is simply the mechanism nodes are using when they are not able to keep up with the write load: to keep replication synchronous, the node that is starting to lag instructs the other nodes that writes should be paused for some time so it does not get too far behind.
If you are not familiar with this notion, you should read this …[Read more]