Slave nodes not in Yarn ResourceManager

Question

I've set up a 3 node Apache Hadoop cluster. On master node, I can see

[hadoop-conf]$ jps
16856 DataNode
17051 SecondaryNameNode
16701 NameNode
21601 ResourceManager
21742 NodeManager
18335 JobHistoryServer

and on slave nodes, I see

[fedora20-template dfs]$ jps
28677 Jps
28510 NodeManager
27449 DataNode

I can see three live nodes from master:50070. However, in the ResourceManager Web UI (http://master:8088/cluster/nodes), I can see only master node. Why are the two slave nodes not in the resource manager? Does that mean they are not part of resources that are used to do mapreduce?

Answer 1

Problem solved. Some configuration should be done in yarn-site.xml to let the nodemanager know where is the resource manager. Specifically, I added this property into yarn-site.xml:

  <property>
    <name>yarn.resourcemanager.hostname</name>
    <value>master</value>
  </property>

Reason: the default value in yarn-default.xml is 0.0.0.0, and many properties use this hostname to contact resource manager, such as

<property>
    <name>yarn.resourcemanager.address</name>
    <value>${yarn.resourcemanager.hostname}:8032</value>
</property>

Answer credits: https://stackoverflow.com/a/22125279/3209177

Answer 2

Ideally yes, the slave nodes are not part of your cluster. Probably because of incorrect cluster setup. But just to be sure run the following command in your shell

hdfs dfsadmin -report

You should be able to get the stats of the data nodes.