def handle_request(layer_id, redis_conn):
    '''handler for any item pulled from worker job queue

    This handler is called every time the worker is able to pop a message
    from the job queue filled by the registry. The worker blocks until a
    message is available. This handler will then attempt to aquire a lock
    for the provided layer_id and if successful, process a diff for the
    layer.

    If the lock for this layer_id has already been aquired for this layer
    the worker will immediately timeout to block for another request.
    '''
    try:
        # this with-context will attempt to establish a 5 minute lock
        # on the key for this layer, immediately passing on LockTimeout
        # if one isn't availble
        with rlock.Lock(redis_conn,
                        "diff-worker-lock",
                        layer_id,
                        expires=60 * 5):
            # first check if a cached result is already available. The registry
            # already does this, but hey.
            diff_data = layers.get_image_diff_cache(layer_id)
            if not diff_data:
                log.info("Processing diff for %s" % layer_id)
                layers.get_image_diff_json(layer_id)
    except rlock.LockTimeout:
        log.info("Another worker is processing %s. Skipping." % layer_id)
handler for any item pulled from worker job queue

    This handler is called every time the worker is able to pop a message
    from the job queue filled by the registry. The worker blocks until a
    message is available. This handler will then attempt to aquire a lock
    for the provided layer_id and if successful, process a diff for the
    layer.

    If the lock for this layer_id has already been aquired for this layer
    the worker will immediately timeout to block for another request.
    
scripts/diff-worker.py