Chapter 21. Configuring Include File Management for HDFS and YARN

Both HDFS and YARN have the ability to control which hosts in the cluster should be included and excluded from participating in the cluster. HDFS uses the dfs.hosts, and dfs.hosts.exclude properties to control which set of datanodes are allowed to connect to the NameNode. YARN uses user-definable files configured through the yarn.resourcemanager.nodes.include-path and yarn.resourcemanager.nodes.exclude-path properties to control which nodes running the NodeManager component are allowed to communicate with the ResourceManager. When the contents of these files are modified both the HDFS NameNode and YARN ResourceManager need to be notified of these changes by invoking the -refreshNodes commands through dfsadmin for HDFS and rmadmin for YARN.

You can configure Ambari to manage these include files for both YARN and HDFS. This feature can be enabled just for HDFS or YARN, or enabled for both services. When enabled, Ambari will manage the associated include/exclude files and update their contents based on the state of hosts within Ambari. When the files are changed, Ambari will also call the necessary refreshNodes commands to update the state of the NameNode and/or ResourceManager.

The table below describes the actions Ambari will take for the following operations:

Add Component: Adding a NodeManager, or DataNode
Delete Component: Removing a NodeManager, or DataNode
Decommission Component: Decommissioning a NodeManager, or DataNode
Recommission Component: Recommissioning a NodeManager, or DataNode

Operation	Include File Actions	Exclude File Actions	Refresh Nodes Call	Triggers Master Restart Indicator
Add Component	Add hostname	Remove hostname	Yes	No
Delete Component	Remove hostname	Remove hostname	No	No
Decommission Component	Remove hostname (YARN only)	Add hostname	Yes	No
Recommission Component	Add hostname (YARN only)	Remove hostname	Yes	No

Enable Include File Management for HDFS

To enable Include File Management for HDFS:

In Ambari, add the manage.include.files=true property to the Advanced hdfs-site configuration section.
Ensure that the dfs.hosts property is configured in the Custom hdfs-site and that it is set to a valid location on the filesystem of the HDFS NameNode. Ensure that the file exists and is owned by the user being used to run the NameNode.
Restart services as prompted by Ambari.

Example Configuration

In Advanced hdfs-site, set manage.include.files=true
In Custom hdfs-site, set dfs.hosts=/etc/hadoop/conf/dfs.include

Enable Include File Management for Yarn

To enable Include File Management for Yarn:

In Ambari, add the manage.include.files=true property to the Advanced yarn-site configuration section.
Ensure that the yarn.resourcemanager.nodes.include-path is set to a valid location on the filesystem of the YARN Resource Manager. If the yarn.resourcemanager.nodes.include-path is not set, add it to the Custom yarn-site configuration.
Restart services as prompted by Ambari.

Example Configuration

In Advanced yarn-site, set manage.include.files=true
In Custom yarn-site, set yarn.resourcemanager.nodes.include-path=/etc/hadoop/conf/yarn.include

Disable Include File Management for HDFS

To disable Include File Management for HDFS:

In Ambari, set the manage.include.files=false property in the Custom hdfs-site configuration section.
In the same configuration section, remove the dfs.hosts property if configured and you no longer want HDFS to use include files for host management.
Restart services as prompted by Ambari.

Disable Include File Management for Yarn

To disable Include File Management for Yarn:

In Ambari, set the manage.include.files=false property in the Custom yarn-site configuration section.
In the same configuration section, remove the yarn.resourcemanager.nodes.include-path property if configured and you no longer want YARN to use include files for host management.
Restart services as prompted by Ambari.