Understanding kafka-coordinator-heartbeat-thread

[mandeepjain]

We were investigating Thread dump of one of the servers and found out there were multiple kafka heartbeat-threads in waiting state.

I wanted to understand why these threads are in waiting state.

[Wzy19930507]

Source code in kafka client class AbstractCoordinator#HeartbeatThread.run, look like

        @Override
        public void run() {
            while (true) {
                // ...
                } else if (!heartbeat.shouldHeartbeat(now)) {
                    // poll again after waiting for the retry backoff in case the heartbeat failed or the
                    // coordinator disconnected
                    AbstractCoordinator.this.wait(rebalanceConfig.retryBackoffMs);
                } else {
                    heartbeat.sentHeartbeat(now);
                    // ...
                }
            }
        }

1. a consumer start a HeartThread
2. kafka client call Heartbeat.entHeartbeat every period heartbeatIntervalMs

[artembilan]

I'm not sure why we have such a discussion here in Spring project.
It looks like something internal to Apache Kafka client by itself: better to ask the question in their community.