MySQL

This page desperately needs to be filled out or brought up to date. If you're familiar with the operations of this part of the site, please help!

FIXME: There's no install info here

• MySQL server tools - setup outline, quick howtos
• http://wp.wikidev.net/Special:Search?search=mysql&fulltext=Search

Installing a new Slave host

In this section, I will describe the steps to take in order to create a new slave from scratch.

To summarize the steps:

  * De-pool another slave from the same cluster, which will be used as the base.
  * Clean up the existing slave from replication errors
  * Install required packages on the new slave server
  * Tweak the configuration file of the new slave
  * Binary copy of relevant data from existing slave to new slave
  * Add both servers to the pool
  * Cross fingers and make sure everything works... 

De-pooling / Clean up / Shutdown

• The file we are going to be working on is: /home/wikipedia/common/wmf-deployment/wmf-config/db-pmtpa.php
• In this file, find the cluster you are working with. In this case, we want to add a slave to the commons db, ergo the cluster is: s2commons
• The 'sectionLoads' array will show the current members of the cluster. The FIRST member is ALWAYS the MASTER! In this case, the master would be db13.
• Pick a slave. For this we will use db3, and we will be working on installing db8 as the new slave.
• De-pool db3 so that we can copy data from it when the data is not changing. In the same array, comment out db3, and sync-file db-pmtpa.php.
• Clean up the slave by running reset-mysql-slave db3.pmtpa.wmnet on Zwinger
• Shut down mysqld on db3 and wait for the shutdown to complete (can take up to 1/2 hour).

Installing required packages on the "new" slave:

• On db8 (our new slave server), install the following:
• * wikimedia-mysql4 (our default mysql server package)
• * pv (to monitor the data transmission as described below)

Tweak configuration file on the new slave:

• edit the /etc/my.cnf file and change the line:

1. id = 1 + zero-filled last 4 digits of internal IP

server-id = 100241

Binary copy:

As usual, there is more than one way to do it. However the most efficient way that was pointed out to me is to use nc+tar combination to transfer everything from one slave to the other. You could just as well use mysql-dump or mydumper, scp and then re-import everything, but it is a lot more time-consuming.