Re: FATAL: bogus data in lock file "postmaster.pid": ""

On Fri, Jan  6, 2012 at 08:28:48AM -0500, Michael Beattie wrote:
> On Fri, Jan 6, 2012 at 6:13 AM, Magnus Hagander <magnus@hagander.net> wrote:
>
>     On Thu, Jan 5, 2012 at 23:19, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>     > Magnus Hagander <magnus@hagander.net> writes:
>     >> On Thu, Jan 5, 2012 at 17:13, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>     >>> I think link(2) would create race conditions of its own.  I'd be
>     >>> inclined to suggest that maybe we should just special-case a zero
>     length
>     >>> postmaster.pid file as meaning "okay to proceed".  In general, garbage
>     >
>     >> That's pretty much what I meant - but with a warning message.
>     >
>     > Actually ... wait a minute.  If we allow that, don't we create a race
>     > condition between two postmasters starting at almost the same instant?
>     > The second one could see the lock file when the first has created but
>     > not yet filled it.
>
>     Good point, yeah, it should do that. But I still think it's rare
>     enough that just special-casing the error message should be enough...
>
>
>
> so just something that does like
>
> stat(filename, &st);
> size = st.st_size;
> if (size == 0)
>    elog(ERROR, "lock file \"%s\" has 0 length.", filename);
>
> somewhere in CreateLockFile in miscinit.c?

I have developed the attached patch to report a zero-length file, as you
suggested.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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