[BUG] The heartbeat does not actually check whether a worker is truly alive when renewing its lease. #1089
Description
Describe the bug
There appears to be a bug in the system.
The heartbeat does not actually check whether a worker is truly alive when renewing its lease. If a worker crashes and fails to notify the heartbeat via a "finished" channel, the heartbeat will continue to renew the lease for this crashed worker. The lease will only expire when the worker's deadline is reached, triggering retry logic. However, until that point, the lease remains active and is only replaced when a new lease takes over. Before the deadline is reached, this zombie worker will continue to occupy a concurrency slot.