Hadoop Distributed File System (HDFS) is a distributed file system designed to run on commodity hardware. It is highly fault-tolerant and designed to be deployed on low-cost hardware. HDFS provides high throughput access to application data and is suitable for applications that have large data sets.
In a Hadoop High Availability (HA) setup, you might encounter an error where the Namenode metadata fails to sync between the active and standby Namenodes. This issue is often indicated by error messages in the logs or a failure in the failover process.
The issue HDFS-043: Namenode Metadata Sync Failure arises when there is a failure in syncing metadata between Namenodes in an HA setup. This can lead to inconsistencies and potential data loss if not addressed promptly. The root cause is often related to misconfiguration or connectivity issues with Zookeeper, which is used to manage the HA state.
To resolve the Namenode metadata sync failure, follow these steps:
Ensure that the HA configuration is correctly set up in the hdfs-site.xml file. Check for the following properties:
<property>
<name>dfs.nameservices</name>
<value>mycluster</value>
</property>
<property>
<name>dfs.ha.namenodes.mycluster</name>
<value>namenode1,namenode2</value>
</property>
Ensure that each Namenode is correctly listed and configured.
Verify that the Zookeeper ensemble is running and reachable. Use the following command to check the status:
zkServer.sh status
Ensure that all Zookeeper nodes are in a healthy state and can communicate with each other.
Ensure that there are no network issues preventing communication between the Namenodes and Zookeeper. Use tools like ping or telnet to verify connectivity.
If the configuration and network are correct, try restarting the Namenodes to re-establish the sync process:
hadoop-daemon.sh stop namenode
hadoop-daemon.sh start namenode
For more detailed information on configuring HA in Hadoop, refer to the official Hadoop High Availability Guide. Additionally, check the Zookeeper Administration Guide for managing Zookeeper ensembles.
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