pg_stop_backup does not complete
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From: "Kevin Grittner" on 23 Feb 2010 14:25 Simon Riggs <simon(a)2ndQuadrant.com> wrote: > The correct resolution is to put in an archive_command that works. One really should ensure that WAL files (or should I now say data? ;-) are flowing before issuing running the pg_start_backup() function. The documentation has always been pretty explicit about that: http://www.postgresql.org/docs/8.4/interactive/continuous-archiving.html | 24.3.2. Making a Base Backup | | The procedure for making a base backup is relatively simple: | | 1. Ensure that WAL archiving is enabled and working. | | 2. Connect to the database as a superuser, and issue the command: | | SELECT pg_start_backup('label'); | ... As long as the SR documentation is equally explicit on this point, you'd have to be blatantly going against the instructions to hit this. Which makes me think that while pg_fail_backup() might actually be a good idea, it's not really needed to solve this, so it's 9.1 material at best. -Kevin -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: David Fetter on 23 Feb 2010 14:38 On Tue, Feb 23, 2010 at 06:58:22PM +0000, Simon Riggs wrote: > On Tue, 2010-02-23 at 09:45 -0800, Josh Berkus wrote: > > > 1) Set up a brand new master with an archive-commmand and > > archive=on. > > > > 2) Start the master > > > > 3) Do a pg_start_backup() > > > > 4) Realize, based on log error messages, that I've misconfigured > > the archive_command. > > > 5) Attempt to shut down the master. Master tells me that > > pg_stop_backup must be run in order to shut down. > > > > 6) Execute pg_stop_backup. > > > > 7) pg_stop_backup waits forever without ever stopping backup. > > Ever 60 seconds, it give me a helpful "still waiting" message, but > > at least in the amount of time I was willing to wait (5 minutes), > > it never completed. > > > > 8) do an immediate shutdown, as it's the only way I can get the > > database unstuck. > > > > With some experimentation, the problem seems to occur when you > > have a failing archive_command and a master which currently has no > > database traffic; for example, if I did some database write > > activity (a createdb) then pg_stop_backup would complete after > > about 60 seconds (which, btw, is extremely annoying, but at least > > tolerable). > > > > This issue is 100% reproduceable. > > IMHO there in no problem in that behaviour. If somebody requests a > backup then we should wait for it to complete. Kevin's suggestion of > pg_fail_backup() is the only sensible conclusion there because it > gives an explicit way out of deadlock. > > ISTM the problem is that you didn't test. Steps 3 and 4 should have > been reversed. Perhaps we should put something in the docs to say > "and test". The correct resolution is to put in an archive_command > that works. +1 for clarifying and extending the docs. Cheers, David. -- David Fetter <david(a)fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fetter(a)gmail.com iCal: webcal://www.tripit.com/feed/ical/people/david74/tripit.ics Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Simon Riggs on 23 Feb 2010 14:39 On Tue, 2010-02-23 at 11:24 -0800, Joshua D. Drake wrote: > This will bite us if we release like this. No it won't. The current behaviour was put there by user request a few releases back. This isn't a 9.0 issue, and as I've said its addressing something that we now longer see as mainstream going forwards. There are plenty of things that will bite us, but not this. -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Robert Haas on 23 Feb 2010 14:49 On Tue, Feb 23, 2010 at 12:52 PM, Joshua D. Drake <jd(a)commandprompt.com> wrote: > On Tue, 2010-02-23 at 09:45 -0800, Josh Berkus wrote: >> Simon, Fujii, All: >> >> While demoing HS/SR at SCALE, I ran into a problem which is likely to be >> a commonly encountered bug when people first setup HS/SR. Here's the >> sequence: >> >> 1) Set up a brand new master with an archive-commmand and archive=on. >> >> 2) Start the master >> >> 3) Do a pg_start_backup() >> >> 4) Realize, based on log error messages, that I've misconfigured the >> archive_command. >> >> 5) Attempt to shut down the master. Master tells me that pg_stop_backup >> must be run in order to shut down. > > If I issue a shutdown, PostgreSQL should do whatever it needs to do to > shutdown; including issuing a pg_stop_backup. Maybe. But for sure, if it doesn't, and instead tells the user to issue pg_stop_backup(), then pg_stop_backup() had better WORK when the user tries to execute it. I gather that the problem is that it has to finish all that outstanding archiving before shutting down, in which case Kevin's suggestion of having a command to abort the backup seems reasonable. I might call it pg_abort_backup() rather than pg_fail_backup(), but... ....Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: "Joshua D. Drake" on 23 Feb 2010 15:09
On Tue, 2010-02-23 at 14:49 -0500, Robert Haas wrote: > > If I issue a shutdown, PostgreSQL should do whatever it needs to do to > > shutdown; including issuing a pg_stop_backup. > > Maybe. But for sure, if it doesn't, and instead tells the user to > issue pg_stop_backup(), then pg_stop_backup() had better WORK when the > user tries to execute it. Right. > I gather that the problem is that it has to > finish all that outstanding archiving before shutting down, in which > case Kevin's suggestion of having a command to abort the backup seems > reasonable. I might call it pg_abort_backup() rather than > pg_fail_backup(), but... > But...? Joshua D. Drake > ...Robert > -- PostgreSQL.org Major Contributor Command Prompt, Inc: http://www.commandprompt.com/ - 503.667.4564 Consulting, Training, Support, Custom Development, Engineering Respect is earned, not gained through arbitrary and repetitive use or Mr. or Sir. -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers |