WAL archive cleanup om master

Hoi,

I've setup a up WAL shipping configuration as described in the wiki. On
the master I have:

archive_mode = on
archive_command = 'cp %p /path_to/archive/%f'

and on the slave in the recovery.conf I have:

archive_cleanup_command = 'pg_archivecleanup /path/to/archive/ %r'
restore_command = 'cp /path/to/archive/%f %p'

In between the two machines I have an rsync process copying the files
from the master to the slave.

My problem is, that the archive_cleanup_command on the slave is
clearing old WAL files, which the rsync on the master just copies again
because they are still on the master.

I can make a script on the master that deletes files older than an
hour, but that will break horribly if the copying breaks for an hour.

Is there a smarter way to do this, like having rsync not copy stuff
already copied once?

Thanks in advance,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> He who writes carelessly confesses thereby at the very outset that he does
> not attach much importance to his own thoughts.
-- Arthur Schopenhauer