Support Questions

Find answers, ask questions, and share your expertise
Announcements
Celebrating as our community reaches 100,000 members! Thank you!

Renaming NameNode HA logical Name "dfs.nameservices" in an existing cluster

avatar
Expert Contributor

Is it supported to modify an existing cluster's NameNode logical name (dfs.nameservices) in an HA configuration ?

I was able to get dfs.nameservices renamed using the following steps, but I want to confirm if this could have some issues that I'm unaware of at this time. The steps involved re-creating the NN HA znode, re-initializing the shared edits for the journal node and performing the bootstrap again for the standby NameNode:

(run the commands as hdfs user)

1) Turn on safemode $ hdfs dfsadmin -safemode enter Safe mode is ON in rm-hdp23n1.novalocal/172.25.17.33:8020 Safe mode is ON in rm-hdp23n3.novalocal/172.25.16.71:8020

2) Perform namenode checkpointing:

$ hdfs dfsadmin -saveNamespace Save namespace successful for rm-hdp23n1.novalocal/172.25.17.33:8020 Save namespace successful for rm-hdp23n3.novalocal/172.25.16.71:8020

3) From Ambari stop all HDFS services.

4) Make the appropriate changes with the properties.

Update "fs.defaultFS" in core-file.xml, And then all the properties in hdfs-site.xml that are related to the HA servicename be modified. For instance, in my cluster I changed the following properties or their values:

"dfs.client.failover.proxy.provider.cluster456" : "org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider",

"dfs.ha.namenodes.cluster456" : "nn1,nn2",

"dfs.namenode.http-address.cluster456.nn1" : "rm-hdp23n1.novalocal:50070",

"dfs.namenode.http-address.cluster456.nn2" : "rm-hdp23n3.novalocal:50070",

"dfs.namenode.https-address.cluster456.nn1" : "rm-hdp23n1.novalocal:50470",

"dfs.namenode.https-address.cluster456.nn2" : "rm-hdp23n3.novalocal:50470",

"dfs.namenode.rpc-address.cluster456.nn1" : "rm-hdp23n1.novalocal:8020",

"dfs.namenode.rpc-address.cluster456.nn2" : "rm-hdp23n3.novalocal:8020",

"dfs.namenode.shared.edits.dir" : "qjournal://rm-hdp23n2.novalocal:8485;rm-hdp23n3.novalocal:8485;rm-hdp23n1.novalocal:8485/cluster456",

"dfs.nameservices" : "cluster456",

5) And then start only the journal nodes (With ZKFC and both NameNodes still in Stopped state) and re-initialize shared edits:

$ hdfs namenode -initializeSharedEdits -force

6) initialize zk node for NN HA: hdfs zkfc -formatZK -force

7) And then start the NameNodes and zkfc on both the nodes.

1 ACCEPTED SOLUTION

avatar
@rmaruthiyodan the steps look fine to me. I actually had to do this myself recently (see this article https://community.hortonworks.com/articles/4632/changing-dfsnameservices-value-after-hdfs-ha-has-b.h...l). I didn't encounter any issues after changing the logical name. Just make sure you also update the Hive Metastore and I think if you use HBase there are some additional changes necessary.

View solution in original post

2 REPLIES 2

avatar
@rmaruthiyodan the steps look fine to me. I actually had to do this myself recently (see this article https://community.hortonworks.com/articles/4632/changing-dfsnameservices-value-after-hdfs-ha-has-b.h...l). I didn't encounter any issues after changing the logical name. Just make sure you also update the Hive Metastore and I think if you use HBase there are some additional changes necessary.

avatar
Master Guru

@rmaruthiyodan, @Jonas Straub

Agreed! We might need to run hive metatool to update existing nameservice URI.