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So you want to monitor your MySql replication database

by bernt & torsten

You have configured your MySql replication, the next step is to perform maintenance and monitor your replication. Percona Toolkit for MySQL is a collection of advanced command-line tools to perform a variety of MySQL server and system tasks.

The Percona Toolkit allows you to amongst many tasks to verify MySQL replication integrity, efficiently archive rows, find duplicate indexes, summarize MySQL servers, analyze queries from logs and tcpdump, collect vital system information when problems occur.

To get started you need to install Percona Toolkit, I’m using Ubuntu as an OS on my servers, installing the percona toolkit was straight forward

apt-get install percona-toolkit

To get a summary of your databases to use the command – pt-mysql-summary

pt-mysql-summary --u=username --p=password

Next, you would want to set up a heartbeat table in your database so you can Monitor MySQL replication delay – for that you will use the pt-heartbeat command.

pt-heartbeat -D wpslavedb --create-table --ask-pass --check --master-server-id 1

You can find the manual for the options here.

pt-heartbeat measures replication lag on a MySQL or PostgreSQL server. You can use it to update a master or monitor a replica. mk-heartbeat depends only on the heartbeat record being replicated to the slave, so it works regardless of the replication mechanism. It works at any depth in the replication hierarchy; for example, it will reliably report how far a slave lags its master’s master’s master.

Start daemonized process to update test.heartbeat table on master:

  pt-heartbeat -D wpslavedb --update -h master-server --daemonize --ask-pass

Monitor replication lag on the slave:

  pt-heartbeat -D wpslavedb --monitor -h slave-server --ask-pass
  pt-heartbeat -D wpslavedb --monitor -h slave-server --dbi-driver Pg --ask-pass

Check slave lag once and exit (using optional DSN to specify slave host):

  pt-heartbeat -D wpslavedb --check h=slave-server --ask-pass

If the replication hierarchy is “master -> slave1 -> slave2” with corresponding server IDs 1, 2 and 3, you can:

  pt-heartbeat --daemonize -D wpslavedb --update -h master --ask-pass
  pt-heartbeat --daemonize -D wpslavedb --update -h slave1 --ask-pass

Then check (or monitor) the replication delay from master to slave2:

  pt-heartbeat -D wpslavedb --master-server-id 1 --check slave2 --ask-pass

Or check the replication delay from slave1 to slave2:

  pt-heartbeat -D wpslavedb --master-server-id 2 --check slave2 --ask-pass

if you developing and writing SQL statements, this command is very useful pt-query-digest – Analyze MySQL queries from logs, processlist, and tcpdump

  pt-query-digest slow.log    // requires you to have slow query logged enabled

There are other tools Percona Toolkit, these that I have shown is what I find useful for my monitoring and maintenance.

If you want to find out the best MySql configuration for your application, you can head over to Percona’s website they have a MySql wizards.

If you liked what I wrote then please feel free to comment below or share.