Re: [Wikitech-l] Another master split

Tim Starling wrote: Looks like I've run out of time. I've repartitioned all the slaves, that was the main thing that required off-peak traffic conditions. We can do the master switch itself during the day on Monday UTC, when there are more sysadmins around. The master partitions are designated s1, s2 and s3 (s for section), assigned as follows: s1: enwiki s2: bgwiki, bgwiktionary, commonswiki, cswiki, dewiki, enwikiquote, enwiktionary, eowiki, fiwiki, idwiki, itwiki, nlwiki, nowiki, plwiki, ptwiki, svwiki, thwiki, trwiki, zhwiki s3: everything else There will also be two additional slave partitions -- sets of servers which only replicate a reduced set of databases: s2a: dewiki s3a: frwiki, jawiki We do this so that holbach and webster, slave servers with only 4GB of memory, will have something useful to do. Holbach will be doing s2a and webster will be doing s3a. The server assignments at present are: s1: db2, db3, ariel, db4, db6, db7 s2: db8, ixia, lomaria s2a: holbach s3: samuel, thistle, db1, db5 s3a: webster The main potential pitfall I can see in the master switch is the possibility that a client with an old configuration may write to the stale copy of the databases in the old master. To avoid this, I'm proposing that we change masters for both s2 and s3, leaving old clients harmlessly attempting to write to a read-only slave. I've enabled binlogs on db8 and thistle so that they can become the new masters. I'm hoping a Dell such as db8 will be able to cope with the master load, which is typically less than the full slave load. It should be fairly straightforward: * switch wiki to read-only * change master assignment in MW * switch master for s2 * switch master for s3 * switch wiki to r/w It should only take a couple of minutes if we script the master switches. -- Tim Starling