Andrew Dunstan wrote:

> Maybe we should look some more at that. Use of file locking was one
> thought I had today after I saw Tom's earlier comments.
> Perl provides a moderately portable flock(), which we use in fact in
> buildfarm to stop it from running more than one at a time on a given repo
> copy.

But does it work over NFS?  On my system, the flock manpage claims it
doesn't, lockf doesn't say and fcntl also doesn't say, but the flock
manpage says fcntl does.  A lot of people runs servers on NFS, even
though we recommend they don't.  And there are those strange hybrids
like SANs, NASes or what have you.

One serious problem is that if the lock doesn't work for some reason
like NFSness, it will fail silently, which is not acceptable.

Alvaro Herrera                      
The PostgreSQL Company - Command Prompt, Inc.

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