The Pub/Sub Subscriber of version 0.22.0-beta uses streaming as its subscription connection by default. This setting cannot be changed, because of the default access of the Subcriber.Builder#setUseStreaming method.
The Problem with the StreamingSubscriberConnection is, that on each re-connection (which occurs quite often) the channelReconnectBackoff duration is doubled. There is no upper limit, nor any reset of the channelReconnectBackoff duration on successful messages.