参数名                --> MemberMetadata 字段
session.timeout.ms   --> MemberMetadata.sessionTimeoutMs
max.poll.interval.ms --> MemberMetadata.rebalanceTimeoutMs

 1   private def completeAndScheduleNextHeartbeatExpiration(group: GroupMetadata, member: MemberMetadata) {
 2     // complete current heartbeat expectation
 3     member.latestHeartbeat = time.milliseconds()
 4     val memberKey = MemberKey(member.groupId, member.memberId)
 5     heartbeatPurgatory.checkAndComplete(memberKey)
 6
 7     // reschedule the next heartbeat expiration deadline
 8     // 计算心跳截止时刻
 9     val newHeartbeatDeadline = member.latestHeartbeat + member.sessionTimeoutMs
10     val delayedHeartbeat = new DelayedHeartbeat(this, group, member, newHeartbeatDeadline, member.sessionTimeoutMs)
11     heartbeatPurgatory.tryCompleteElseWatch(delayedHeartbeat, Seq(memberKey))
12   }
13
14   // 心跳过期
15   def onExpireHeartbeat(group: GroupMetadata, member: MemberMetadata, heartbeatDeadline: Long) {
16     group.inLock {
17       if (!shouldKeepMemberAlive(member, heartbeatDeadline)) {
18         info(s"Member ${member.memberId} in group ${group.groupId} has failed, removing it from the group")
19         removeMemberAndUpdateGroup(group, member)
20       }
21     }
22   }
23
24   private def shouldKeepMemberAlive(member: MemberMetadata, heartbeatDeadline: Long) =
25     member.awaitingJoinCallback != null ||
26       member.awaitingSyncCallback != null ||
27       member.latestHeartbeat + member.sessionTimeoutMs > heartbeatDeadline

if (coordinatorUnknown()) {if (findCoordinatorFuture != null || lookupCoordinator().failed())// the immediate future check ensures that we backoff properly in the case that no// brokers are available to connect to.AbstractCoordinator.this.wait(retryBackoffMs);
} else if (heartbeat.sessionTimeoutExpired(now)) {// the session timeout has expired without seeing a successful heartbeat, so we should// probably make sure the coordinator is still healthy.
    markCoordinatorUnknown();
} else if (heartbeat.pollTimeoutExpired(now)) {// the poll timeout has expired, which means that the foreground thread has stalled// in between calls to poll(), so we explicitly leave the group.
    maybeLeaveGroup();
} else if (!heartbeat.shouldHeartbeat(now)) {// poll again after waiting for the retry backoff in case the heartbeat failed or the// coordinator disconnectedAbstractCoordinator.this.wait(retryBackoffMs);
} else {heartbeat.sentHeartbeat(now);sendHeartbeatRequest().addListener(new RequestFutureListener<Void>() {@Overridepublic void onSuccess(Void value) {synchronized (AbstractCoordinator.this) {heartbeat.receiveHeartbeat(time.milliseconds());}}@Overridepublic void onFailure(RuntimeException e) {synchronized (AbstractCoordinator.this) {if (e instanceof RebalanceInProgressException) {// it is valid to continue heartbeating while the group is rebalancing. This// ensures that the coordinator keeps the member in the group for as long// as the duration of the rebalance timeout. If we stop sending heartbeats,// however, then the session timeout may expire before we can rejoin.
                    heartbeat.receiveHeartbeat(time.milliseconds());} else {heartbeat.failHeartbeat();// wake up the thread if it's sleeping to reschedule the heartbeatAbstractCoordinator.this.notify();}}}});
}

//maxPollInterval 即 rebalanceTimeoutMs
public boolean pollTimeoutExpired(long now) {return now - lastPoll > maxPollInterval;
}