Search Results for: flow control

Monitoring MySQL flow control in Percona XtraDB Cluster 5.6

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 and wsrep_flow_control_paused_ns. Which one should you use? What is flow control? Flow control does not exist with regular MySQL replication, […]

Galera Flow Control in Percona XtraDB Cluster for MySQL

Last week at Percona Live, I delivered a six-hour tutorial about Percona XtraDB Cluster (PXC) for MySQL.  I actually had more material than I covered (by design), but one thing I regret we didn’t cover was Flow control.  So, I thought I’d write a post covering flow control because it is important to understand. What […]

Semi-Sync replication performance in MySQL 5.7.4 DMR

I was interested to hear about semi-sync replication improvements in MySQL’s 5.7.4 DMR release and decided to check it out.  I previously blogged about poor semi-sync performance and was pretty disappointed from semi-sync’s performance across WAN distances back then, particularly with many client threads. The Test The basic environment of these tests was: AWS EC2 […]

Percona XtraDB Cluster/ Galera with Percona Monitoring Plugins

The Percona Monitoring Plugins (PMP) provide some free tools to make it easier to monitor PXC/Galera nodes.  Monitoring broadly falls into two categories: alerting and historical graphing, and the plugins support Nagios and Cacti, respectively, for those purposes. Graphing An update to the PMP this summer (thanks to our Remote DBA team for supporting this!) added a Galera-specific host template that […]

Measuring Max Replication Throughput on Percona XtraDB Cluster with wsrep_desync

Checking throughput with async MySQL replication Replication throughput is the measure of just how fast the slaves can apply replication (at least by my definition).  In MySQL async replication this is important to know because the single-threaded apply nature of async replication can be a write performance bottleneck.  In a production system, we can tell […]

Taking backups on Percona XtraDB Cluster (without stalls!)

I occasionally see customers who are taking backups from their PXC clusters that complain that the cluster “stalls” during the backup.  As I wrote about in a previous blog post, often these stalls are really just Flow Control.  But why would a backup cause Flow control? Most backups I know of (even Percona XtraBackup) take […]

MySQL Webinar: Percona XtraDB Cluster Operations, June 26

Percona XtraDB Cluster (PXC) was released over a year ago and since then there has been tremendous interest and adoption.  There’s plenty of talks that explain the fundamentals of PXC, but we’re starting to reach a threshold where it’s easier to find folks with PXC in production and such the need for more advanced talks […]

MySQL net_write_timeout vs wait_timeout and protocol notes

In my previous post I mentioned you might need to increase net_write_timeout to avoid connection being aborted and now I think I should have better explained that. MySQL uses a lot of different timeout variables at different stages. For example when connection is just being established connect_timeout is used. When server waits for another query […]