Thread: BUG #15749: ERROR: dsa_area could not attach to segment | FATAL: cannot unpin a segment that is not pinned
BUG #15749: ERROR: dsa_area could not attach to segment | FATAL: cannot unpin a segment that is not pinned
From
PG Bug reporting form
Date:
The following bug has been logged on the website: Bug reference: 15749 Logged by: Torrey Johnson Email address: torrey@interactiveshift.com PostgreSQL version: 11.2 Operating system: Linux Ubuntu 16.04 Description: Hi there, after upgrading our postgres version from 10.5 to 11.2, we noticed that our parallel query was causing DynamicSharedMemoryControlLock on our queries, and locking everything up, causing our connections to expand and ending up killing our database. I found this thread, and it's pretty much the exact same thing: https://www.postgresql.org/message-id/flat/458c691a-1b2d-7a70-1c04-58361b894011%40gmail.com#bab0f00fb877880d0fbaadadd2624ce2 I've disabled 'max_parallel_workers_per_gather = 0', and it hasn't happened since. These were the settings when this started to happening max_parallel_workers_per_gather = 4 max_worker_processes = 8 max_parallel_workers = 8 Here's the errors from my postgres logs after seeing DynamicSharedMemoryControlLock fill up in 'pg_stat_activity': 2019-03-28 22:24:32.728 EDT [24283] ignite@ignite_production ERROR: dsa_area could not attach to segment 2019-03-28 22:24:32.728 EDT [24283] ignite@ignite_production STATEMENT: SELECT "team_activity_views".* FROM "team_activity_views" WHERE "team_activity_views"."team_id" = $1 LIMIT $2 2019-03-28 22:24:32.728 EDT [63006] FATAL: terminating connection due to administrator command 2019-03-28 22:24:32.728 EDT [63006] STATEMENT: SELECT "team_activity_views".* FROM "team_activity_views" WHERE "team_activity_views"."team_id" = $1 LIMIT $2 2019-03-28 22:24:32.728 EDT [63005] FATAL: terminating connection due to administrator command 2019-03-28 22:24:32.728 EDT [63005] STATEMENT: SELECT "team_activity_views".* FROM "team_activity_views" WHERE "team_activity_views"."team_id" = $1 LIMIT $2 2019-03-28 22:24:32.729 EDT [63005] FATAL: cannot unpin a segment that is not pinned 2019-03-28 22:24:32.730 EDT [1110] LOG: background worker "parallel worker" (PID 63006) exited with exit code 1 Any help or update on this would be great. I would love to turn this option back on. Thanks
Re: BUG #15749: ERROR: dsa_area could not attach to segment | FATAL: cannot unpin a segment that is not pinned
From
Sergei Kornilov
Date:
Hello This bug should be already fixed in stable branch and will be shipped in next minor release. Until the fix is released, thesimplest workaround is to disable parallel query with SET max_parallel_workers_per_gather = 0 if you're affected by thebug. It's a rare timing bug, but some workloads seem to be more prone to it, so unfortunately it went undetected for a long time. If you're interested, related discussion and patch was here: https://www.postgresql.org/message-id/flat/20190207014719.GJ29720%40telsasoft.com regards, Sergei