I'm also wondering here. In my opinion, it's because the JM can not confirm whether the TM is lost or it's a temporary network trouble and will recover soon, since I can see in the log that akka has got a Connection refused but JM still sends a heartbeat request to the lost TM until it reaches heartbeat timeout. But I'm not sure if it's indeed designed like this.
I would really appreciate it if anyone who knows more details could answer. Thanks.
