The AMPS Python client handles most incoming messages and takes appropriate action. Some messages are unexpected or occur only in very rare circumstances. The AMPS Python client provides a way for clients to process these messages. Rather than providing handlers for all of these unusual events, AMPS provides a single handler function for messages that can't be handled during normal processing.
Your application registers this handler by setting the last_chance_message_handler for the client. This handler is called when the client receives a message that can't be processed by any other handler. This is a rare event, and typically indicates an unexpected condition.
For example, if a client publishes a message that AMPS cannot parse, AMPS returns a failure acknowledgment. This is an unexpected event, so AMPS does not include an explicit handler for this event, and failure acknowledgments are received in the method registered as the last_chance_message_handler.
Your application is responsible for taking any corrective action needed. For example, if a message publication fails, your application can decide to republish the message, publish a compensating message, log the error, stop publication altogether, or any other action that is appropriate.