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 ----- 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
