Zookeeper server not responding.

[Pramod Srinivasan]

Hello Everyone,

I am using Zookeeper 3.5.1-alpha and I see a problem when I am using a 2 node 
setup.

Node 1 Zookeeper logs:

2020-01-11 11:29:52,141 [myid:2147483653] - INFO  
[QuorumPeerListener:QuorumCnxManager$Listener@631] - My election bind port: 
0.0.0.0/0.0.0.0:61898
2020-01-11 11:29:52,149 [myid:2147483653] - ERROR 
[WorkerSender[myid=2147483653]:NIOServerCnxnFactory$1@92] - Thread 
Thread[WorkerSender[myid=2147483653],5,main] died
java.lang.NullPointerException
        at 
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(Unknown
 Source)
        at java.util.concurrent.LinkedBlockingQueue.poll(Unknown Source)
        at 
org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.run(FastLeaderElection.java:462)
        at java.lang.Thread.run(Unknown Source)
2020-01-11 11:29:52,161 [myid:2147483653] - INFO  
[QuorumPeer[myid=2147483653](plain=/0:0:0:0:0:0:0:0:61896)(secure=disabled):QuorumPeer@986]
 - LOOKING

Node 2 Zookeeper logs:

2020-01-11 11:29:51,852 [myid:2147483652] - WARN  
[WorkerSender[myid=2147483652]:QuorumCnxManager@459] - Cannot open channel to 
2147483653 at election address /128.0.0.5:61898
java.net.ConnectException: Connection refused
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
        at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
        at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
        at java.net.SocksSocketImpl.connect(Unknown Source)
        at java.net.Socket.connect(Unknown Source)
        at 
org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:444)
        at 
org.apache.zookeeper.server.quorum.QuorumCnxManager.connectOne(QuorumCnxManager.java:485)
        at 
org.apache.zookeeper.server.quorum.QuorumCnxManager.toSend(QuorumCnxManager.java:421)
        at 
org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.process(FastLeaderElection.java:486)
        at 
org.apache.zookeeper.server.quorum.FastLeaderElection$Messenger$WorkerSender.run(FastLeaderElection.java:465)
        at java.lang.Thread.run(Unknown Source)

Zookeeper server on the nodes never recover from this state and clients are 
unable to connect to the server. Any hint on what the problem is based on the 
back trace on Node 1 logs? Is this a Zookeeper server code issue or a setup 
issue?

Thanks,
Pramod