Re: Idea for improving buildfarm robustness

I wrote:
> It strikes me that a different approach that might be of value would
> be to re-read postmaster.pid and make sure that (a) it's still there
> and (b) it still contains the current postmaster's PID. This would
> be morally equivalent to what Jim suggests above, and it would dodge
> the checkpointer-destroys-the-evidence problem, and it would have the
> additional advantage that we'd notice when a brain-dead DBA decides
> to manually remove postmaster.pid so he can start a new postmaster.
> (It's probably far too late to avoid data corruption at that point,
> but better late than never.)

> This is still not bulletproof against all overwrite-with-a-backup
> scenarios, but it seems like a noticeable improvement over what we
> discussed yesterday.

Here's a rewritten patch that looks at postmaster.pid instead of
pg_control. It should be effectively the same as the prior patch in terms
of response to directory-removal cases, and it should also catch many
overwrite cases.

regards, tom lane