Re: Postmaster hangs

Karen Pease <meme(at)daughtersoftiresias(dot)org> writes:
> It'll get through about three or four of them (out of hundreds) before
> it locks up. Now, before lockup, postmaster is very active. It shows
> up on top. The computer's hard drives clack nonstop. Etc. But once it
> locks up (without warning), all of that stop. Postmaster does nothing.
> The computer goes silent. I can't ctrl-break the psql process. If I
> try to start a new psql process, it won't get past the password prompt
> -- psql will hang. All Apache processes involving postgres queries
> hang. The postgres server cannot be restarted by any normal means (the
> only solution I've found that works is a reboot). And so forth.

This sounds to me like it's a kernel problem, possibly triggered by
misbehaving disk hardware. What you might try to confirm is a kill -9
on whichever postgres backend seems to be stuck. If that fails to
remove the process, then it's definitely a kernel issue --- try googling
"uninterruptible disk wait" and similar phrases.

The cases that I've run into personally have been due to poor error
handling for a disk failure condition in a kernel-level disk driver.
If that's what it is for you, the bottom-level problem might be an
unreadable disk block somewhere. Or it might just be a garden variety
kernel bug. What's the platform?

regards, tom lane