April 23, 2014

How to log slow queries on Slave in MySQL 5.0 with pt-query-digest

Working as a Percona Support Engineer, every day we are seeing lots of issues related to MySQL replication. One very common issue is slave lagging. There are many reasons for slave lag but one common reason is that queries are taking more time on slave then master. How to check and log those long-running queries?  From […]

Changing an async slave of a PXC cluster to a new Master using 5.6 and GTID

Before Percona XtraBackup 2.1.7 and Percona XtraDB Cluster 5.6.15-25.3, rsync was the only SST method supporting GTID in the way that it was possible to move an asynchronous slave from one Galera node to another one (related bug). Indeed, previous versions of Percona XtraBackup didn’t copy any binary log and due to that, moving the […]

Beware of MySQL 5.6 server UUID when cloning slaves

The other day I was working on an issue where one of the slaves was showing unexpected lag. Interestingly with only the IO thread running the slave was doing significantly more IO as compared to the rate at which the IO thread was fetching the binary log events from the master. I found this out […]

Enabling crash-safe slaves with MySQL 5.6

Being able to configure slaves to be crash-safe is one of the major improvements of MySQL 5.6 with regards to replication. However we noticed confusion on how to enable this feature correctly, so let’s clarify how it should be done. In short 1. Stop MySQL on slave 2. Add relay_log_info_repository = TABLE and relay_log_recovery = […]

Another reason why SQL_SLAVE_SKIP_COUNTER is bad in MySQL

It is everywhere in the world of MySQL that if your replication is broken because an event caused a duplicate key or a row was not found and it cannot be updated or deleted, then you can use ‘ STOP SLAVE; SET GLOBAL SQL_SLAVE_SKIP_COUNTER=1; START SLAVE; ’ and be done with it. In some cases this is fine and you can repair the […]

Changing an async slave of a PXC cluster to a new Master

Async and PXC A common question I get about Percona XtraDB Cluster is if you can mix it with asynchronous replication, and the answer is yes!  You can pick any node in your cluster and it can either be either a slave or a master just like any other regular MySQL standalone server (Just be […]

How to create a new (or repair a broken) GTID based slave with Percona XtraBackup

Percona XtraBackup 2.0.7 has been published with support for GTID based replication. As promised, here is the step-by-step guide on how to create a new GTID based slave (or repair a broken one) using XtraBackup. The process is pretty straightforward. 1- Take a backup from any server on the replication environment, master or slave:

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Disconnecting a replication slave is easier with MySQL 5.5+ (RESET SLAVE vs. RESET SLAVE ALL)

It’s not uncommon to promote a server from slave to master. One of the key things to protect your data integrity is to make sure that the promoted slave is permanently disconnected from its old master. If not, it may get writes from the old master, which can cause all kinds of data corruption. MySQL […]

How to create/restore a slave using GTID replication in MySQL 5.6

MySQL 5.6 is GA! Now we have new things to play with and in my personal opinion the most interesting one is the new Global Transaction ID (GTID) support in replication. This post is not an explanation of what is GTID and how it works internally because there are many documents about that: http://dev.mysql.com/doc/refman/5.6/en/replication-gtids-concepts.html One […]

How to STOP SLAVE on Amazon RDS read replica

We are doing a migration from Amazon RDS to EC2 with a customer. This, unfortunately, involves some downtime – if you are an RDS user, you probably know you can’t replicate an RDS instance to an external server (or even EC2). While it is annoying, this post isn’t going to be a rant on how […]