What is the method for switching the primary node in Hadoop?
The method for switching the main node in Hadoop involves manually executing the following steps:
- Stop the current master node: First, it is necessary to stop the current master node. You can use the command “hadoop-daemon.sh stop namenode” to stop the NameNode service.
- Backing up and restoring data: Before switching the primary node, it is important to ensure that data backup and recovery have been completed. You can use Hadoop’s HDFS command line tool or other tools for backing up and restoring data.
- Modify the configuration file: Open the hdfs-site.xml file in the Hadoop configuration file, and locate the dfs.namenode.rpc-address property. Change the value of this property to the hostname and port number of the new master node.
- Format the new master node: Perform a formatting operation on the new master node to ensure that the metadata is correctly initialized on the new master node. You can use the command hdfs namenode -format to format the new master node.
- Start the new master node: Use the command start-dfs.sh to start the new master node. This will launch the NameNode and its related services.
- Verify the switch: Use the command ‘hadoop dfsadmin -report’ to confirm that the master node has successfully switched. Ensure that the new master node is running and has taken over the functions of the previous master node.
Please note that switching the primary node may have an impact on the Hadoop cluster, so thorough planning and testing should be done before performing this operation.
