def _callback_handler(self, message, callback):
"""Call callback with deserialized message.
Messages that are processed without exception are ack'ed.
If the message processing generates an exception, it will be
ack'ed if ack_on_error=True. Otherwise it will be .reject()'ed.
Rejection is better than waiting for the message to timeout.
Rejected messages are immediately requeued.
"""
ack_msg = False
try:
msg = rpc_common.deserialize_msg(message.payload)
callback(msg)
ack_msg = True
except Exception:
if self.ack_on_error:
ack_msg = True
LOG.exception(_("Failed to process message"
" ... skipping it."))
else:
LOG.exception(_("Failed to process message"
" ... will requeue."))
finally:
if ack_msg:
message.ack()
else:
message.reject()