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Issues with region servers in Azure HDInsight

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This article describes troubleshooting steps and possible resolutions for issues when interacting with Azure HDInsight clusters.

Scenario: Unassigned regions

Issue

When running hbase hbck command, you see an error message similar to:

multiple regions being unassigned or holes in the chain of regions

From the Apache HBase Master UI, you can see the number of regions that are unbalanced across all region servers. Then, you can run hbase hbck command to see holes in the region chain.

Cause

Holes may be the result of offline regions.

Resolution

Fix the assignments. Follow the steps below to bring the unassigned regions back to normal state:

  1. Sign in to the HDInsight HBase cluster using SSH.

  2. Run hbase zkcli command to connect with ZooKeeper shell.

  3. Run rmr /hbase/regions-in-transition or rmr /hbase-unsecure/regions-in-transition command.

  4. Exit zookeeper shell by using exit command.

  5. Open the Apache Ambari UI, and then restart the Active HBase Master service.

  6. Run hbase hbck command again (without any further options). Check the output and ensure that all regions are being assigned.

Scenario: Dead region servers

Issue

Region servers fail to start.

Cause

Multiple splitting WAL directories.

  1. Get list of current WALs: hadoop fs -ls -R /hbase/WALs/ > /tmp/wals.out.

  2. Inspect the wals.out file. If there are too many splitting directories (starting with *-splitting), the region server is probably failing because of these directories.

Resolution

  1. Stop HBase from Ambari portal.

  2. Execute hadoop fs -ls -R /hbase/WALs/ > /tmp/wals.out to get fresh list of WALs.

  3. Move the *-splitting directories to a temporary folder, splitWAL, and delete the *-splitting directories.

  4. Execute hbase zkcli command to connect with zookeeper shell.

  5. Execute rmr /hbase-unsecure/splitWAL.

  6. Restart HBase service.

Next steps

If you didn't see your problem or are unable to solve your issue, visit one of the following channels for more support:

  • Get answers from Azure experts through Azure Community Support.

  • Connect with @AzureSupport - the official Microsoft Azure account for improving customer experience. Connecting the Azure community to the right resources: answers, support, and experts.

  • If you need more help, you can submit a support request from the Azure portal. Select Support from the menu bar or open the Help + support hub. For more detailed information, review How to create an Azure support request. Access to Subscription Management and billing support is included with your Microsoft Azure subscription, and Technical Support is provided through one of the Azure Support Plans.