Work Preserving Recovery for YARN Components

Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)

CDH 5.2 introduces work preserving recovery for the YARN ResourceManager and NodeManager. With work preserving recovery enabled, if a ResourceManager or NodeManager restarts, no in-flight work is lost. You can configure work preserving recovery separately for a ResourceManager or NodeManager. You can enable work preserving recovery whether or not you use ResourceManager High Availability.

Configuring Work Preserving Recovery Using Cloudera Manager

Enabling Work Preserving Recovery on ResourceManager with Cloudera Manager

Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)

If you use Cloudera Manager and you enable YARN (MRv2) ResourceManager High Availability, work preserving recovery is enabled by default for the ResourceManager.

Disabling Work Preserving Recovery on ResourceManager Using Cloudera Manager

To disable Work Preserving Recovery for the ResourceManager:

  1. Go to the YARN service.
  2. Click the Configuration tab.
  3. Search for Enable ResourceManager Recovery.
  4. In the Enable ResourceManager Recovery field, clear the ResourceManager Default Group checkbox.
  5. Click Save Changes.

Enabling Work Preserving Recovery on NodeManager with Cloudera Manager

Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)

The default value for the recovery directory is /var/lib/hadoop-yarn/yarn-nm-recovery.

Work preserving recovery is enabled by default in Cloudera Manager managed clusters.

These are the steps to enable work preserving recovery for a given NodeManager, if needed:
  1. Edit the advanced configuration snippet for yarn-site.xml on that NodeManager, and set the value of yarn.nodemanager.recovery.enabled to true.
  2. Configure the directory on the local filesystem where state information is stored when work preserving recovery is enabled.
    1. Go to the YARN service.
    2. Click the Configuration tab.
    3. Search for NodeManager Recovery Directory.
    4. Enter the directory path in the NodeManager Recovery Directory field (for example, /var/lib/hadoop-yarn/yarn-nm-recovery).
    5. Click Save Changes.

Configuring Work Preserving Recovery Using the Command Line

Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)

After enabling YARN (MRv2) ResourceManager High Availability, add the following property elements to yarn-site.xml on the ResourceManager and all NodeManagers.
  1. Set the value of yarn.resourcemanager.work-preserving-recovery.enabled to true to enable work preserving recovery for the ResourceManager, and set the value of yarn.nodemanager.recovery.enabled to true for the NodeManager.
  2. For each NodeManager, configure the directory on the local filesystem where state information is stored when work preserving recovery is enabled, Set yarn.nodemanager.recovery.dir to a local filesystem directory. The default value is ${hadoop.tmp.dir}/yarn-nm-recovery. This location usually points to the /tmp directory on the local filesystem. Because many operating systems do not preserve the contents of the /tmp directory across a reboot, Cloudera strongly recommends changing the location of yarn.nodemanager.recovery.dir to a directory under the root partition. If the drive which hosts this directory fails, the NodeManager will also fail. The example below uses /home/cloudera/recovery.
  3. Configure a valid RPC address for the NodeManager by setting yarn.nodemanager.address to an address with a specific port number (such as 0.0.0.0:45454). Ephemeral ports (default is port 0) cannot be used for the NodeManager's RPC server; this could cause the NodeManager to use different ports before and after a restart, preventing clients from connecting to the NodeManager. The NodeManager RPC address is also important for auxiliary services that run in a YARN cluster.

Auxiliary services should be designed to support recoverability by reloading the previous state after a NodeManager restarts. An example auxiliary service, the ShuffleHandler service for MapReduce, follows the correct pattern for an auxiliary service that supports work preserving recovery of the NodeManager.

For more information, see Starting, Stopping, and Restarting Services.

Example Configuration for Work Preserving Recovery

Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)

The following example configuration can be used with a Cloudera Manager advanced configuration snippet or added to yarn-site.xml directly if you do not use Cloudera Manager. Adjust the configuration to suit your environment. 
<property>
  <name>yarn.resourcemanager.work-preserving-recovery.enabled</name>
  <value>true</value>
  <description>Whether to enable work preserving recovery for the Resource Manager</description>
</property>
<property>
  <name>yarn.nodemanager.recovery.enabled</name>
  <value>true</value>
  <description>Whether to enable work preserving recovery for the Node Manager</description>
</property>
<property>
  <name>yarn.nodemanager.recovery.dir</name>
  <value>/home/cloudera/recovery</value>
  <description>The location for stored state on the Node Manager, if work preserving recovery 
    is enabled.</description>
</property>
<property>
  <name>yarn.nodemanager.address</name>
  <value>0.0.0.0:45454</value>
</property>