UnknownHostException kafka

问题:

I am trying to setup a Kafka cluster (the first node in the cluster actually).

I have a single node zookeeper cluster setup. I am setting up kafka on a separate node.

Both running CentOS 6.4, running IPV6 which is a bit of a PITA. I verified that the machines can talk to each other using netcat.

When I startup kafka, I am getting the following exception (which causes kafka to shut down). EDIT: I got kafka starting, I had to set the host.name property in the server.config file.

I was able to create a test topic and send messages just fine from the kafka server.

However, I get the same error when trying to consume the messages.

Any help, suggestions?

bin/kafka-console-consumer.sh --zookeeper zk1:2181 --topic test --from-beginning Exception in thread "main" java.net.UnknownHostException: kafka: kafka: Name or service not known at java.net.InetAddress.getLocalHost(InetAddress.java:1473) at kafka.consumer.ZookeeperConsumerConnector.<init>(ZookeeperConsumerConnector.scala:107) at kafka.consumer.ZookeeperConsumerConnector.<init>(ZookeeperConsumerConnector.scala:128) at kafka.consumer.Consumer$.create(ConsumerConnector.scala:89) at kafka.consumer.ConsoleConsumer$.main(ConsoleConsumer.scala:178) at kafka.consumer.ConsoleConsumer.main(ConsoleConsumer.scala) Caused by: java.net.UnknownHostException: kafka: Name or service not known at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:901) at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1293) at java.net.InetAddress.getLocalHost(InetAddress.java:1469) ... 5 more

回答1:

When you run > bin/kafka-console-consumer.sh command kafka loads a ConsoleConsumer, which will attempt to create a consumer with an auto generated consumer id. The way Kafka generates the consumer id is to concatenate the name of the local host to it. So, in the problem was the fact that java could not resolve the ip address for local host on the Open Stack VM I am working with.

So the answer was that the Open Stack VM was resolving the local host name to kafka, which is the name of the VM. I had everything setup in the Kafka and Zookeeper instances as kafka1.

So, when java was calling getLocalHost, it was trying to find the IP Address for kafka, which I did not have in my /etc/hosts file.

I simply added an entry for kafka in my /etc/hosts file and everything started working wonderfully!!!

I would have thought it would resolve to localhost, but it did not, it resolved to the name of the vm, kafka.

回答2:

As noplay pointed out the issue was that Kafka wasn't able to resolve the correct IP, this may happen for example on you EC2 instances running in private subnets without assignment of public IP. The solution summarized:

hostname

Which will show you the host name, something like ip-10-180-128-217. Then just update your /etc/hosts

sudo nano /etc/hosts

edit, e.g.

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4 ip-10-180-128-217