Snapshot
Creates a snapshot from the requested subscription. Snapshots are used in Seek operations, which allow you to manage message acknowledgments in bulk. That is, you can set the acknowledgment state of messages in an existing subscription to the state captured by a snapshot. If the snapshot already exists, returns ALREADY_EXISTS. If the requested subscription doesn't exist, returns NOT_FOUND. If the backlog in the subscription is too old -- and the resulting snapshot would expire in less than 1 hour -- then FAILED_PRECONDITION is returned. See also the Snapshot.expire_time field. If the name is not provided in the request, the server will assign a random name for this snapshot on the same project as the subscription, conforming to the resource name format (https://cloud.google.com/pubsub/docs/admin#resource_names). The generated name is populated in the returned Snapshot object. Note that for REST API requests, you must specify a name in the request. Auto-naming is currently not supported for this resource.
Properties
The snapshot is guaranteed to exist up until this time. A newly-created snapshot expires no later than 7 days from the time of its creation. Its exact lifetime is determined at creation by the existing backlog in the source subscription. Specifically, the lifetime of the snapshot is 7 days - (age of oldest unacked message in the subscription). For example, consider a subscription whose oldest unacked message is 3 days old. If a snapshot is created from this subscription, the snapshot -- which will always capture this 3-day-old backlog as long as the snapshot exists -- will expire in 4 days. The service will refuse to create a snapshot that would expire in less than 1 hour after creation.