BUG #13895: Hot Standby locked replaying auto vacuum against pg_catalog.pg_statistics

The following bug has been logged on the website:

Bug reference:      13895
Logged by:          Dimitri Fontaine
Email address:      dimitri@2ndQuadrant.fr
PostgreSQL version: 9.3.10
Operating system:   Linux
Description:

I witnessed a case where I had no time to extract information about it, so
it's all from memory, sorry about that.

We had several Hot Standby nodes in 9.3.x used for load balancing read only
queries. All queries were stuck, and pg_locks showed they were refused a
lock against pg_catalog.pg_statistics.

The lock owner PID was not to be found in the pg_stat_activity system view,
for it was the replay process.

I don't remember how I got to the conclusion it was replaying specifically
autocavuum activity, but if that's helpful, that is what I remember it was
about.

My todo list includes extracting useful information next time it happens,
before we just restart the standby (a restart fixes the availability /
situation).

Regards,