title: Kafka Controller could not connect to brokers
body: <p>I've a 3 node Kafka cluster(version 0.10.1.0). I've followed the steps on <a href="https://kafka.apache.org/documentation#security" rel="noreferrer">kafka security documentation</a>. Here are the related configurations of one of my Kafka servers.</p>
  <pre><code>listeners=SSL://myhostname:9093
  security.inter.broker.protocol=SSL
  advertised.listeners=SSL://myhostname:9093
  # In order to enable hostname verification
  ssl.endpoint.identification.algorithm=HTTPS
  
  ssl.client.auth=required
  
  # certificate file locations
  ssl.keystore.location=/location/server1.keystore.jks
  ssl.keystore.password=changeit
  ssl.key.password=changeit
  ssl.truststore.location=/location/server.truststore.jks
  ssl.truststore.password=changeit
  
  # Supported TLS versions
  ssl.enabled.protocols=TLSv1.2,TLSv1.1,TLSv1
  </code></pre>
  <p>I've defined 3 different keystores for all my Kafka servers and signed them with the same CA. When I start the Kafka servers the controller log constantly logs the following warning log.</p>
  <pre><code>WARN [Controller-0-to-broker-2-send-thread], Controller 0's connection to broker host3:9093 (id: 2 rack: null) was unsuccessful (kafka.controller.RequestSendThread)
  java.io.IOException: Connection to host3:9093 (id: 2 rack: null) failed
      at kafka.utils.NetworkClientBlockingOps$.awaitReady$1(NetworkClientBlockingOps.scala:83)
      at kafka.utils.NetworkClientBlockingOps$.blockingReady$extension(NetworkClientBlockingOps.scala:93)
      at kafka.controller.RequestSendThread.brokerReady(ControllerChannelManager.scala:230)
      at kafka.controller.RequestSendThread.liftedTree1$1(ControllerChannelManager.scala:182)
      at kafka.controller.RequestSendThread.doWork(ControllerChannelManager.scala:181)
      at kafka.utils.ShutdownableThread.run(ShutdownableThread.scala:63)
  WARN [Controller-0-to-broker-0-send-thread], Controller 0's connection to broker host1:9093 (id: 0 rack: null) was unsuccessful (kafka.controller.RequestSendThread)
  java.io.IOException: Connection to host1:9093 (id: 0 rack: null) failed
      at kafka.utils.NetworkClientBlockingOps$.awaitReady$1(NetworkClientBlockingOps.scala:83)
      at kafka.utils.NetworkClientBlockingOps$.blockingReady$extension(NetworkClientBlockingOps.scala:93)
      at kafka.controller.RequestSendThread.brokerReady(ControllerChannelManager.scala:230)
      at kafka.controller.RequestSendThread.liftedTree1$1(ControllerChannelManager.scala:182)
      at kafka.controller.RequestSendThread.doWork(ControllerChannelManager.scala:181)
      at kafka.utils.ShutdownableThread.run(ShutdownableThread.scala:63)
  WARN [Controller-0-to-broker-1-send-thread], Controller 0's connection to broker host2:9093 (id: 1 rack: null) was unsuccessful (kafka.controller.RequestSendThread)
  java.io.IOException: Connection to host2:9093 (id: 1 rack: null) failed
      at kafka.utils.NetworkClientBlockingOps$.awaitReady$1(NetworkClientBlockingOps.scala:83)
      at kafka.utils.NetworkClientBlockingOps$.blockingReady$extension(NetworkClientBlockingOps.scala:93)
      at kafka.controller.RequestSendThread.brokerReady(ControllerChannelManager.scala:230)
      at kafka.controller.RequestSendThread.liftedTree1$1(ControllerChannelManager.scala:182)
      at kafka.controller.RequestSendThread.doWork(ControllerChannelManager.scala:181)
      at kafka.utils.ShutdownableThread.run(ShutdownableThread.scala:63)
  </code></pre>
  <p>It seems to me more serious than a warning.</p>
  <p>Do you have any idea what may be the problem?</p>
  <p>Thanks in advance.</p>