Optional. If this field set to true, the system will respond immediately even if it there are no messages available to return in the Pull response. Otherwise, the system may wait (for a bounded amount of time) until at least one message is available, rather than returning no messages. Warning: setting this field to true is discouraged because it adversely impacts the performance of Pull operations. We recommend that users do not set this field.

Required. The maximum number of messages to return for this request. Must be a positive integer. The Pub/Sub system may return fewer than the number specified.