Hi folks,
I've been seeing some curious behaviour on a postgres server I administer.
Intermittently (one or two times a week), all queries on that host are simultaneously blocked for extended periods (10s of seconds).
The blocked queries are trivial & not related to locking - I'm seeing slowlogs of the form:
`LOG: duration: 22627.299 ms statement: SET client_encoding='''utf-8''';`
where this is the first statement on a fresh connection.
It happens even for connections from the same host - so it doesn't appear to be e.g. network slowness, if that is even counted in query duration.
Does anyone have any hints for where to look for a cause?
Thanks,
Patrick
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Set up information:
Postgres version: PostgreSQL 9.6.5 on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609, 64-bit
Full Table and Index Schema: not applicable, I think
EXPLAIN ANALYSE: n/a
Hardware: AWS i3.2xlarge
Maintenance Setup: autovacuum yes, but the times it runs don't correlate to the incidences of slow queries
WAL settings: shipped to S3 with wal-e, stored on same disk for interim period