A message and its corresponding acknowledgment ID.
This ID can be used to acknowledge the
The approximate number of times that Cloud Pub/Sub has
attempted to deliver the associated message to a subscriber.
More precisely, this is 1 + (number of NACKs) + (number of
ack_deadline exceeds) for this message.
A NACK is any call to ModifyAckDeadline with a 0 deadline.
An ack_deadline exceeds event is whenever a message is not
acknowledged within ack_deadline. Note that ack_deadline is
initially Subscription.ackDeadlineSeconds, but may get
extended automatically by the client library.
Upon the first delivery of a given message,
delivery_attempt will have a value of 1. The value is
calculated at best effort and is approximate.
If a DeadLetterPolicy is not set on the subscription, this
will be 0.