MuleSoft Google Pub/Sub Connector Message Listener Limit Exceeded Behavior

The Mulesoft ‌"onMessage" listener source acknowledge (ACK) messages which were correctly processed on the Flow end and does not acknowledge (NACK) if there is an error in the Flow automatically.

In MuleSoft, it is not possible to mix batch processing, which is used in publish operations and the processing in subscriber (On Message Listener). Messages are received in a sequence, not in batches that's why the batch configuration is not part of this on message listener source.

MuleSoft limit exceeded behavior is triggered in the source if there is a specified amount or memory size of outstanding messages (messages where no Ack() or Nack() was performed), so there are multiple threads/consumers consuming 5 messages but the Flow still does not end and there are more messages incoming. If the limit exceeds behavior is set to BLOCK, source does not start processing new messages and waits until messages are processed either ACK-ed/NACK-ed or throws an exception in case of THROW_EXCEPTION behavior is set. If it is set to IGNORE, then Flow control does not take into account any limits and processes messages without any control of delivery rate.