Two nodes can own a same lock at same time ------------------------------------------ Key: JGRP-2220 URL: https://issues.jboss.org/browse/JGRP-2220 Project: JGroups Issue Type: Bug Affects Versions: 3.4 Environment: Two nodes cluster with jgroup 3.4.0 alpha2 Reporter: Xiao Li Assignee: Bela Ban Fix For: 4.0.7 We have a two node cluster with following protocol stack for distributed lock. lock.protocolStack=UDP(bind_addr=myIP;bind_port=31562;mcast_addr=239.255.166.17;mcast_port=31569;ip_ttl=32;mcast_send_buf_size=150000;mcast_recv_buf_size=80000):PING(timeout=2000;num_initial_members=3):MERGE2(min_interval=5000;max_interval=10000):FD_ALL(interval=5000;timeout=20000):VERIFY_SUSPECT(timeout=1500):pbcast.NAKACK(retransmit_timeout=300,600,1200,2400,4800):UNICAST(timeout=5000):pbcast.STABLE(desired_avg_gossip=20000):FRAG(frag_size=8096):pbcast.GMS(join_timeout=5000;print_local_addr=true):CENTRAL_LOCK(num_backups=2) We use the following call to get a lock for one node. lock = lockManager.getLock(lockId); lock.tryLock(Long.MAX_VALUE, TimeUnit.MILLISECONDS); where lockManager is an object of LockService and lock is a Lock object. Another node is waiting on the lock at same method call. When the node owning the lock release the lock with the call lock.unlock(), the node waiting on the lock gets the lock and the lock is deleted from the node owned the lock. When the JVM for the node that released the lock restarted, it can also get same lock. So two nodes own the lock at same time. If I don't call lock.unlock() before shutting down the node, it waits for the lock as expected when its JVM starts up.