Configuring HMS for high availability

To provide failover to a secondary Hive metastore if your primary instance goes down, you need to know how to add a Metastore role in Cloudera Manager and configure a property.

Multiple HMS instances run in active/active mode. No load balancing occurs. An HMS client always hits the first instance unless it is down. In this case, the client scans the hive.metastore.uris property that lists the HMS instances for a replacement HMS. The second HMS is the designated replacement if hive.metastore.uri.selection is set to SEQUENTIAL (recommended and the default); otherwise, the replacement is selected randomly from the list if hive.metastore.uri.selection is set to RANDOM.
Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)
  1. In Cloudera Manager, click Clusters > Hive > Configuration.
  2. Take one of the following actions:
    • If you have a cluster secured by Kerberos, search for Hive Delegation Token Store, which specifies storage for the Kerberos token as described below.
    • If you have an unsecured cluster, skip the next step.
  3. Select org.apache.hadoop.hive.thrift.DBTokenStore, and save the change.
    Storage for the Kerberos delegation token is defined by the hive.cluster.delegation.token.store.class property. The available choices are Zookeeper, the Metastore, and memory. Cloudera recommends using the database by setting the org.apache.hadoop.hive.thrift.DBTokenStore property.
  4. Click Instances > Actions > Add Role Instances
  5. In Assign Roles, in Metastore Server, click Select Hosts.
  6. In Hosts Selected, scroll and select the host that you want to serve as the backup Metastore, and click OK.
  7. Click Continue until you exit the wizard.
  8. Start the Metastore role on the host from the Actions menu.
    The hive.metastore.uris property is updated automatically.
  9. To check or to change the hive.metastore.uri.selection property, go to Clusters > Hive > Configurations, and search for Hive Service Advanced Configuration Snippet (Safety Valve) for hive-site.xml.
  10. Add the property and value (SEQUENTIAL or RANDOM).