On Thu, 10 Apr 2008, Dag Wieers wrote:
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 :)
Just noticed that the flock utility is fairly recent (since util-linux
2.13) which means that on most systems you do not have it.
For RHEL that means only available since RHEL5 :-(
That could be one of the reasons to have it as part of rsync (to
facilitate the distribution of a cron-job or simply make sure your mirrors
are using best practices without too much complexity).
--
-- dag wieers, [EMAIL PROTECTED], http://dag.wieers.com/ --
[Any errors in spelling, tact or fact are transmission errors]
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