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Toolserver:Admin:Change the replication master

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Before you change the master, you need the new master position. It's usually in the server admin log, but if not, ask for it in #wikimedia-tech. If the master was changed by the WMF-guys because of a schema-change it is important to wait until the (then) old master was modified by the WMF-guys too.

If the master host changed

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If the master is changing, you need to reconfigure SQL-Proxy to use the new master. Then choose one of the following options, based on the replication type.

For a MySQL-replicated cluster

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  • Stop the MySQL slave: STOP SLAVE;
  • Change the MySQL master position: CHANGE MASTER TO master_log_pos=..., master_log_file='...';
  • Restart replication: START SLAVE;

For a trainwreck-replicated cluster

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  • Stop the appropriate trainwreck instance: svcs trainwreck; svcadm disable trainwreck:instance
  • Wait for the reader and writer threads to exit (tail -f /var/svc/log/network-trainwreck:instance.log)
  • Delete the file 0.logpos, which will be in the statedir defined in /etc/trainwreck/instance.conf.
  • Run trainwreck manually: /opt/local/bin/trainwreck -af /etc/trainwreck/instance.conf -F <logfile> -p <position>
  • Stop it: /opt/local/bin/twctl -c /etc/trainwreck/instance.conf shutdown
  • Start it properly: svcadm enable trainwreck:instance

Category:Admin:Database

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