Toolserver:Replication lag

Toolserver uses database replication to mirror the Wikimedia database used by the live servers. Each update to the live database is logged, and the Toolserver databases follow this log to make the same updates. The Toolserver databases may fall behind the Wikimedia database, resulting in a situation where the toolserver data represents the state of the Wikimedia database some time in the past. The replication lag (replag) tells how far behind the Wikimedia databases the Toolserver databases have fallen. Database crashes and expensive queries can cause the replag to dramatically increase.

The current replag can be viewed here, or by typing @replag in the #wikimedia-toolserver IRC channel on freenode.

When invoked, the replag bot (currently tsbot) will output something like this: s1: 0s [no change]; s1-c: 2s [+0.00 sec/sec]; s1-fast: 0s [no change]; s1-fast-c: 2s [+0.00 sec/sec]; s2: 2s [-0.00 sec/sec]; s2-c: 2s [+0.00 sec/sec]; s3: 1s [no change]; s3-c: 2s [+0.00 sec/sec]; s5: 2s [-0.00 sec/sec]; s6: 6s [+0.01 sec/sec] (8m 0s sample)

This shows the amount of lag on the various databases and the rate of change for each. The "-c" suffix indicates the lag of the copy of the Commons database on that server. The "-fast" suffix indicates the lag of the secondary, faster copy of the database. More information about the "fast" databases is available here.

The current specific databases used by tsbot are:
 * s1 &rarr; enwiki_p
 * s1-c &rarr; commonswiki_p
 * s1-fast &rarr; enwiki_p
 * s1-fast-c &rarr; commonswiki_p
 * s2 &rarr; itwiki_p
 * s2-c &rarr; commonswiki_p
 * s3 &rarr; eswiki_p
 * s3-c &rarr; commonswiki_p
 * s5 &rarr; dewiki_p
 * s6 &rarr; frwiki_p

Determining specific wiki lag
To figure out how lagged your wiki is, look up the server column at Wiki server assignments. For example, the aawiki_p database is listed under server 3. So tools referencing the aawiki_p database will be lagged however much s3 reports as being lagged.