WARN Exception while shutting down acceptor. (org.apache.zookeeper.server.quorum.Leader) java.net.SocketException: Socket closed

Question

I have a strimzi kafka installation deployed in Kubernetes using the below command:

helm upgrade --install kafka --set replicaCount=1 --set persistence.storageClass=kafka-storage .

I get exception in zookeper:

2025年09月29日 13:26:54,835 INFO Snapshotting: 0x30000d605 to /var/lib/zookeeper/data/version-2/snapshot.30000d605 (org.apache.zookeeper.server.persistence.FileTxnSnapLog) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,836 INFO Snapshot taken in 2 ms (org.apache.zookeeper.server.ZooKeeperServer) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,864 INFO Peer state changed: leading - synchronization (org.apache.zookeeper.server.quorum.QuorumPeer) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,864 INFO Have quorum of supporters, sids: [[1],[1]]; starting up and setting last processed zxid: 0xba133e00000000 (org.apache.zookeeper.server.quorum.Leader) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,864 WARN Unexpected exception (org.apache.zookeeper.server.quorum.QuorumPeer) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
java.util.NoSuchElementException
 at java.base/java.util.HashMap$HashIterator.nextNode(HashMap.java:1599)
 at java.base/java.util.HashMap$KeyIterator.next(HashMap.java:1620)
 at org.apache.zookeeper.server.quorum.Leader.getDesignatedLeader(Leader.java:886)
 at org.apache.zookeeper.server.quorum.Leader.startZkServer(Leader.java:1537)
 at org.apache.zookeeper.server.quorum.Leader.lead(Leader.java:696)
 at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:1552)
2025年09月29日 13:26:54,864 INFO Shutting down (org.apache.zookeeper.server.quorum.Leader) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,864 INFO Shutdown called. For the reason Forcing shutdown (org.apache.zookeeper.server.quorum.Leader) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,864 INFO Peer state changed: looking (org.apache.zookeeper.server.quorum.QuorumPeer) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,864 WARN PeerState set to LOOKING (org.apache.zookeeper.server.quorum.QuorumPeer) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,864 INFO LOOKING (org.apache.zookeeper.server.quorum.QuorumPeer) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,864 INFO New election. My id = 1, proposed zxid=0x30000d605 (org.apache.zookeeper.server.quorum.FastLeaderElection) [QuorumPeer[myid=1](plain=127.0.0.1:12181)(secure=[0:0:0:0:0:0:0:0]:2181)]
2025年09月29日 13:26:54,865 WARN Exception while shutting down acceptor. (org.apache.zookeeper.server.quorum.Leader) [LearnerCnxAcceptorHandler-dev-cluster-zookeeper-0.dev-cluster-zookeeper-nodes.kafka.svc/10.233.75.32:2888]
java.net.SocketException: Socket closed
 at java.base/sun.nio.ch.NioSocketImpl.endAccept(NioSocketImpl.java:694)
 at java.base/sun.nio.ch.NioSocketImpl.accept(NioSocketImpl.java:767)
 at java.base/java.net.ServerSocket.implAccept(ServerSocket.java:675)
 at java.base/java.net.ServerSocket.platformImplAccept(ServerSocket.java:641)
 at java.base/java.net.ServerSocket.implAccept(ServerSocket.java:617)
 at java.base/java.net.ServerSocket.implAccept(ServerSocket.java:574)
 at org.apache.zookeeper.server.quorum.UnifiedServerSocket.accept(UnifiedServerSocket.java:139)
 at org.apache.zookeeper.server.quorum.Leader$LearnerCnxAcceptor$LearnerCnxAcceptorHandler.acceptConnections(Leader.java:521)
 at org.apache.zookeeper.server.quorum.Leader$LearnerCnxAcceptor$LearnerCnxAcceptorHandler.run(Leader.java:504)
 at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
 at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
 at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
 at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
 at java.base/java.lang.Thread.run(Thread.java:840)
2025年09月29日 13:26:54,865 INFO Notification: my state:LOOKING; n.sid:1, n.state:LOOKING, n.leader:1, n.round:0xba1355, n.peerEpoch:0xba133e, n.zxid:0x30000d605, message format version:0x2, n.config version:0x0 (org.apache.zookeeper.server.quorum.FastLeaderElection) [WorkerReceiver[myid=1]]

Do you know how I can fix this?

• Jakub: I do not think the command you shared has any meaning to anyone else than you as it is likely using some custom Helm Chart you have and nobody knows what does it actually creates. You should probabl share the custom resource you use instead.
• OneCricketeer: You should use kraft mode anyway