如果是在同一台机器（localhost），Kafka Client工作正常，Producer和Consumer都能正常发送和接收消息，但是一旦部署到两台机器，则默认配置的话不能正常工作。会出现“kafka.common.FailedToSendMessageException: Failed to send messages after 3 tries”的错误。
[2020-01-09 12:42:43,841] ERROR Failed to send requests for topics cache-message with correlation ids in [17,24] (kafka.producer.async.DefaultEventHandler)
[2020-01-09 12:42:43,841] ERROR Error in handling batch of 1 events (kafka.producer.async.ProducerSendThread)
kafka.common.FailedToSendMessageException: Failed to send messages after 3 tries.
at kafka.producer.async.DefaultEventHandler.handle(DefaultEventHandler.scala:90)
at kafka.utils.Utils$.read(Utils.scala:376)
at kafka.network.BoundedByteBufferReceive.readFrom(BoundedByteBufferReceive.scala:54)
at kafka.network.Receive$class.readCompletely(Transmission.scala:56)
at kafka.network.BoundedByteBufferReceive.readCompletely(BoundedByteBufferReceive.scala:29)
at kafka.network.BlockingChannel.receive(BlockingChannel.scala:100)
at kafka.producer.SyncProducer.liftedTree1$1(SyncProducer.scala:74)
at kafka.producer.SyncProducer.kafka$producer$SyncProducer$$doSend(SyncProducer.scala:71)
at kafka.producer.SyncProducer.send(SyncProducer.scala:112)
at kafka.client.ClientUtils$.fetchTopicMetadata(ClientUtils.scala:53)
at kafka.producer.BrokerPartitionInfo.updateInfo(BrokerPartitionInfo.scala:82)
at kafka.producer.BrokerPartitionInfo.getBrokerPartitionInfo(BrokerPartitionInfo.scala:49)
at kafka.producer.async.DefaultEventHandler.kafka$producer$async$DefaultEventHandler$$getPartitionListForTopic(DefaultEventHandler.scala:186)
at kafka.producer.async.DefaultEventHandler$$anonfun$partitionAndCollate$1.apply(DefaultEventHandler.scala:150)
at kafka.producer.async.DefaultEventHandler$$anonfun$partitionAndCollate$1.apply(DefaultEventHandler.scala:149)
at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:60)
at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:47)
at kafka.producer.async.DefaultEventHandler.partitionAndCollate(DefaultEventHandler.scala:149)
at kafka.producer.async.DefaultEventHandler.dispatchSerializedData(DefaultEventHandler.scala:95)
at kafka.producer.async.DefaultEventHandler.handle(DefaultEventHandler.scala:72)
at kafka.producer.async.ProducerSendThread.tryToHandle(ProducerSendThread.scala:104)
at kafka.producer.async.ProducerSendThread$$anonfun$processEvents$3.apply(ProducerSendThread.scala:87)
at kafka.producer.async.ProducerSendThread$$anonfun$processEvents$3.apply(ProducerSendThread.scala:67)
at scala.collection.immutable.Stream.foreach(Stream.scala:526)
at kafka.producer.async.ProducerSendThread.processEvents(ProducerSendThread.scala:66)
at kafka.producer.async.ProducerSendThread.run(ProducerSendThread.scala:44)
[2020-01-09 12:42:43,500] WARN Fetching topic metadata with correlation id 19 for topics [Set(cache-message)] from broker [id:2,host:192.168.0.108,port:2181] failed (kafka.client.ClientUtils$)
java.io.EOFException: Received -1 when reading from channel, socket has likely been closed.
at kafka.utils.Utils$.read(Utils.scala:376)
解决方法其实很简单，只需要在Kafka的配置文件server.properties中，设置好主机名即可：
# Hostname the broker will bind to. If not set, the server will bind to all interfaceshost.name=queue-server1
究其原因，其实从注释里，我们可以知道，这是一个指定broker的地址（严格来说是所监听的网络接口，或者网卡），同时，也可以看出它还和下面的属性相关。
# Hostname the broker will advertise to producers and consumers. If not set, it uses the
# value for “host.name” if configured. Otherwise, it will use the value returned from
# java.net.InetAddress.getCanonicalHostName().
#advertised.host.name=
也就是说，producer和consumer是通过这个主机名（advertised.host.name）来连接broker的，而如果这个值没有设置，则会使用上面的host.name的值，如果上面的host.name也没有设置，则会使用java.net.InetAddress.getCanonicalHostName()获取的值。
从Zookeeper中可以看出，默认的时候该broker是localhost，从其他机器访问当然不可能成功。
