Unhandled exception caught in InterBrokerSendThread

In kraft mode, if listeners and advertised.listeners are not configured with host addresses, the host parameter value of Listener in BrokerRegistrationRequestData will be null. When the broker is started, a null pointer exception will be thrown, causing startup failure.

A feasible solution is to replace the empty host of endPoint in advertisedListeners with InetAddress.getLocalHost.getCanonicalHostName in Broker Server when building networkListeners.

The following is the debug log:

before fixing:

[2021-04-21 14:15:20,032] DEBUG (broker-2-to-controller-send-thread org.apache.kafka.clients.NetworkClient 522) [broker-2-to-controller] Sending BROKER_REGISTRATION request with header RequestHeader(apiKey=BROKER_REGIS
TRATION, apiVersion=0, clientId=2, correlationId=6) and timeout 30000 to node 2: BrokerRegistrationRequestData(brokerId=2, clusterId='nCqve6D1TEef3NpQniA0Mg', incarnationId=X8w4_1DFT2yUjOm6asPjIQ, listeners=[Listener(n
ame='PLAINTEXT', host=null, port=9092, securityProtocol=0)], features=[], rack=null)
[2021-04-21 14:15:20,033] ERROR (broker-2-to-controller-send-thread kafka.server.BrokerToControllerRequestThread 76) [broker-2-to-controller-send-thread]: unhandled exception caught in InterBrokerSendThread
java.lang.NullPointerException
at org.apache.kafka.common.message.BrokerRegistrationRequestData$Listener.addSize(BrokerRegistrationRequestData.java:515)
at org.apache.kafka.common.message.BrokerRegistrationRequestData.addSize(BrokerRegistrationRequestData.java:216)
at org.apache.kafka.common.protocol.SendBuilder.buildSend(SendBuilder.java:218)
at org.apache.kafka.common.protocol.SendBuilder.buildRequestSend(SendBuilder.java:187)
at org.apache.kafka.common.requests.AbstractRequest.toSend(AbstractRequest.java:101)
at org.apache.kafka.clients.NetworkClient.doSend(NetworkClient.java:525)
at org.apache.kafka.clients.NetworkClient.doSend(NetworkClient.java:501)
at org.apache.kafka.clients.NetworkClient.send(NetworkClient.java:461)
at kafka.common.InterBrokerSendThread.$anonfun$sendRequests$1(InterBrokerSendThread.scala:104)
at kafka.common.InterBrokerSendThread.$anonfun$sendRequests$1$adapted(InterBrokerSendThread.scala:99)
at kafka.common.InterBrokerSendThread$$Lambda$259/910445654.apply(Unknown Source)
at scala.collection.IterableOnceOps.foreach(IterableOnce.scala:563)
at scala.collection.IterableOnceOps.foreach$(IterableOnce.scala:561)
at scala.collection.AbstractIterable.foreach(Iterable.scala:919)
at kafka.common.InterBrokerSendThread.sendRequests(InterBrokerSendThread.scala:99)
at kafka.common.InterBrokerSendThread.pollOnce(InterBrokerSendThread.scala:73)
at kafka.server.BrokerToControllerRequestThread.doWork(BrokerToControllerChannelManager.scala:368)
at kafka.utils.ShutdownableThread.run(ShutdownableThread.scala:96)
[2021-04-21 14:15:20,034] INFO (broker-2-to-controller-send-thread kafka.server.BrokerToControllerRequestThread 66) [broker-2-to-controller-send-thread]: Stopped

after fixing:

[2021-04-21 15:05:01,095] DEBUG (BrokerToControllerChannelManager broker=2 name=heartbeat org.apache.kafka.clients.NetworkClient 512) [BrokerToControllerChannelManager broker=2 name=heartbeat] Sending BROKER_REGISTRATI
ON request with header RequestHeader(apiKey=BROKER_REGISTRATION, apiVersion=0, clientId=2, correlationId=0) and timeout 30000 to node 2: BrokerRegistrationRequestData(brokerId=2, clusterId='nCqve6D1TEef3NpQniA0Mg', inc
arnationId=xF29h_IRR1KzrERWwssQ2w, listeners=[Listener(name='PLAINTEXT', host='hdpxxx.cn', port=9092, securityProtocol=0)], features=[], rack=null)