For a while now I've known that sending a SIGINT can trigger a CHECKPOINT, but 
I don't know if this is intentional or a bug. Logs from today:

> 2013-03-20_18:21:43.27642 LOG:  received fast shutdown request
> 2013-03-20_18:21:43.27645 LOG:  aborting any active transactions
> 2013-03-20_18:21:43.27647 FATAL:  terminating connection due to administrator 
> command
> 2013-03-20_18:22:14.25763 FATAL:  the database system is shutting down
> 2013-03-20_18:22:14.26401 LOG:  checkpoint starting: shutdown immediate
> 2013-03-20_18:25:36.98507 LOG:  checkpoint complete: wrote 6403 buffers 
> (2.3%); 0 transaction log file(s) added, 0 removed, 5 recycled; write=41.450 
> s, sync=156.157 s, total=202.943 s; sync files=50, longest=29.057 s, 
> average=3.123 s

> 2013-03-20_18:25:37.65570 FATAL:  the database system is shutting down
> 2013-03-20_18:25:37.71735 LOG:  online backup mode canceled

And I believe this is where the db restarted:

> 2013-03-20_18:25:37.71739 DETAIL:  "backup_label" was renamed to 
> "backup_label.old".
> 2013-03-20_18:25:45.39001 LOG:  loaded library "auto_explain"
> 2013-03-20_18:25:45.39647 LOG:  loaded library "pg_stat_statements"
> 2013-03-20_18:26:04.67932 LOG:  could not create socket for statistics 
> collector: Protocol not supported
> 2013-03-20_18:26:04.67939 LOG:  trying another address for the statistics 
> collector
> 2013-03-20_18:26:05.01894 LOG:  connection received: host=172.16.4.24 
> port=55414
> 2013-03-20_18:26:05.01903 FATAL:  the database system is starting up
> 2013-03-20_18:26:05.41153 LOG:  autovacuum launcher started
> 2013-03-20_18:26:05.41160 LOG:  database system is ready to accept connections


Just shy of 5 minutes to do a fast shutdown/restart.

What I'm trying to determine is whether or not it's a bug for postmaster to 
CHECKPOINT during a fast shutdown or a documentation bug that a fast shutdown 
may cause a CHECKPOINT, which will delay the database being restarted.

I've run in to this before and in some scripts I run a CHECKPOINT before 
sending a SIGINT, which reduces the size of the CHECKPOINT, but doesn't 
necessarily eliminate it all of the time. In fact, I'm not sure it happens 100% 
of the time either, but today I was bit by this shutdown/startup delay and 
thought I'd inquire or submit a small doc patch. Thanks in advance. -sc



--
Sean Chittenden
s...@chittenden.org



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