Notifying a publisher of life-cycle events for topic subscription

摘要

A message broker of a publish-subscribe messaging system (e.g., using the MQTT protocol or other publish-subscribe protocol) detects a life-cycle event for topic subscription and notifies a publisher of the life-cycle event. The message broker may detect a transition in a number of subscribers to a topic from zero subscribers to one or more subscribers or from one or more subscribers to zero subscribers. In response, the message broker provides an indication to the publisher that the number of subscribers to the topic has transitioned from zero to one or more (or from one or more to zero). This causes the publisher to begin publishing messages on the publisher's topic (or to stop publishing messages on the publisher's topic).