retain
Parameters
value
Indicates whether to retain acknowledged messages. If true, then messages are not expunged from the subscription's backlog, even if they are acknowledged, until they fall out of the message_retention_duration window. This must be true if you would like to `Seek` to a timestamp (https://cloud.google.com/pubsub/docs/replay-overview#seek_to_a_time) in the past to replay previously-acknowledged messages.