On Fri, Jan 14, 2011 at 11:19, Heikki Linnakangas <heikki.linnakan...@enterprisedb.com> wrote: > On 14.01.2011 08:45, Fujii Masao wrote: >> >> On Fri, Jan 14, 2011 at 4:13 AM, Magnus Hagander<mag...@hagander.net> >> wrote: >>>> >>>> At the end of the backup by walsender, it forces a switch to a new >>>> WAL file and waits until the last WAL file has been archived. So we >>>> should change postmaster so that it doesn't cause the archiver to >>>> end before walsender ends when shutdown is requested? >>> >>> Um. I have to admit I'm not entirely following what you mean enough to >>> confirm it, but it *sounds* correct :-) >>> >>> What scenario exactly is the problematic one? >> >> 1. Smart shutdown is requested while walsender is sending a backup. >> 2. Shutdown causes archiver to end. >> (Though shutdown sends SIGUSR2 to walsender to exit, walsender >> running backup doesn't respond for now) >> 3. At the end of backup, walsender calls do_pg_stop_backup, which >> forces a switch to a new WAL file and waits until the last WAL file >> has >> been archived. >> *BUT*, since archiver has already been dead, walsender waits for >> that forever. > > Not only does it wait forever, but it writes the end-of-backup WAL record > after bgwriter has already exited and written the shutdown checkpoint > record. > > I think postmaster should treat a walsender as a regular backend, until it > has started streaming. > > We can achieve that by starting up the child as PM_CHILD_ACTIVE, and > changing the state to PM_CHILD_WALSENDER later, when streaming is started. > Looking at the postmaster.c, that should be safe, postmaster will treat a > backend as a regular backend anyway until it has connected to shared memory. > It is *not* safe to switch a walsender back to a regular process, but we > have no need to do that.
Seems reasonable to me. I've applied a patch that exits base backups when the postmaster is shutting down - I'm happily waiting for Heikki to submit one that changes the shutdown logic in the postmaster :-) -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/ -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
