The minimum time by which the deadline for each incoming message is extended.
While waiting for an ack or nack from the application the Cloud Pub/Sub C++ client library will extend the deadline by at least this amount. The default minimum extension is 1 minute. An application may wish to reduce this extension so that the Pub/Sub service will resend a message sooner when it does not hear back from a Subscriber. An application may wish to increase this extension time to avoid duplicate message delivery.
