Incidents/20161021-Maps

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Summary

Between 18:50 UTC and 19:20 UTC, October 21st, maps.wikimedia.org stopped rendering tiles due to Cassandra backend being unavailable.

Timeline

18:50 UTC: cassandra wrongly reinitialized on maps2004.codfw.wmnet, deleting all cassandra data on maps2004. Kartotherian starts failing with org.apache.cassandra.exceptions.UnavailableException: Cannot achieve consistency level LOCAL_ONE.
19:20 UTC: traffic redirected to maps eqiad cluster, user traffic is served again without error
19:40 UTC: full deployment of new traffic configuration
21:13 UTC: permissions are reset on maps/cassandra codfw cluster, kartotherian starts working again on the codfw clsuter

Conclusions

The main trigger for this is human error.
maps/cassandra has a replication factor of 1 on the "system_auth" keyspace. This means that loosing one node potentially breaks authentication.

Actionables

increase replication factor on system_auth keyspace task T149074