Hadoop Multi-Node Cluster: exception: java.net.ConnectException: Connection refused

Question

I have set up 4 nodes hadoop cluster using http://pingax.com/install-apache-hadoop-ubuntu-cluster-setup/ :

Namenode: node04 Datanode: node01 Datanode: node02 Datanode: node03

I can see only two nodes(node01,node03) running in my cluster. Node02 has an log with error message as:

2015-12-11 10:15:18,698 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: node04/127.17.0.224:9000. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2015-12-11 10:15:19,699 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: node04/127.17.0.224:9000. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2015-12-11 10:15:20,699 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: node04/127.17.0.224:9000. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)

Every nodes /etc/hosts contains following:

127.0.0.1       localhost

127.17.0.221    node01
127.17.0.222    node02
127.17.0.223    node03
127.17.0.224    node04
# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

And /etc/hadoop/masters contains node04 , /etc/hadoop/slaves contains node01 node02 and node03

Would you please help me understand how to get to it? Thanks!

Answer 1

Perform these actions:

1. Go to node02 and run telnet node04 9000 and ping node04 commands to confirm there is connectivity between node02 and node04
2. On all nodes check whether core-site.xml and hdfs-site.xml have the same contents

Answer 2

1. Check ssh and sshd
2. ssh connection between the nodes
3. Check port binding details ( Hadoop Datanodes cannot find NameNode )

Also refer https://wiki.apache.org/hadoop/ServerNotAvailable