Online Verification That Master and Slaves are in Sync
In October 2008, Baron posted How to Check MySQL Replication Integrity Continually. Here at Pythian we have developed a method based on that post, and added “verifying that masters and slaves are in sync” to our standard battery of tests.
We call it “Continual replication sync checking”. This article will explain how it works, how to test and make the procedure non-blocking, benchmarks from the real world, issues we encountered along the way, and finally Pythian’s procedure of setting up continual replication sync in a new environment.
At the 2010 MySQL User Conference & Expo, my co-worker Danil Zburivsky did a presentation about this, and you can get the slides in ODP (Open Office) format or watch the 46-minute video on YouTube.
How it works
On the master, mk-table-checksum is run. In order to make the checksum operation online, we use the modulo and offset features of mk-table-checksum to checksum only part of the data at a time. The checksum is run (from cron) on the master and replicates to the slave. The results are captured in a result table, and a separate process checks the result table and notifies us of any discrepancies.
Read the rest of this entry . . .
