RFE: Lockfile option for use in cronjobs

[Dag Wieers]

On Wed, 2 Apr 2008, Matt McCutchen wrote:

> On Mon, 2008-03-31 at 11:43 +0200, Dag Wieers wrote:
>> Looking for an easy way to prevent a repetitive rsync to be running
>> multiple times, I was wondering if it could be useful to have an option
>> like:
>>
>>  	--pidfile /some/path/rsync-mirror-org.pid
>>
>> So that rsync can be run directly from cron without requiring a wrapper
>> script to do pidfile handling.
>>
>> This way rsync on startup could check the pid-file, see if another rsync
>> is using this pid, and bail out with an error if it is. Otherwise clean up
>> the stale pidfile and continue.
>>
>> I think this would be very useful to instruct mirrors how to configure it,
>> rather than providing some script that needs local customizations.
>
> I'm not convinced that a pidfile is better implemented in rsync than in
> a wrapper script, which could be distributed in support/ of the source
> tree.  If you don't care about actually having the pid in the file, you
> could use the flock(1) utility, which executes a command while holding a
> flock(2) lock on a specified file:
>
> flock --nonblock /some/path/rsync-mirror-org.lock rsync ...
>
> If the process goes away, the lock will too, so no manual cleanup of
> stale locks is needed.

The flock utility is great. I learn something new everyday :)

Thanks a lot !
-- 
--   dag wieers,  dag at wieers.com,  http://dag.wieers.com/   --
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