question Re: HA Hadoop core in Archives of Support Questions (Read Only)

HA Hadoop core

majnam — Tue, 05 Dec 2017 18:05:43 GMT

I'm trying to make HA Hadoop client for Spark job (need for spark warehouse) which will switch from NN1 to NN2 if NN1 breaks down.

public class ConfigFactoryTest {
    public static void main(String [] args) throws IOException {


        HdfsConfiguration conf = new HdfsConfiguration(true);
        conf.set("fs.defaultFS", "hdfs://bigdata5.int.ch:8020");
        conf.set("fs.default.name", conf.get("fs.defaultFS"));
        conf.set("dfs.nameservices","hdfscluster");
        conf.set("dfs.ha.namenodes.nameservice1", "nn1,nn2");
        conf.set("dfs.namenode.rpc-address.hdfscluster.nn1","bigdata1.int.ch:8020");
        conf.set("dfs.namenode.rpc-address.hdfscluster.nn2", "bigdata5.int.ch:8020");
        conf.set("dfs.client.failover.proxy.provider.hdfscluster","org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider");


          FileSystem fs = FileSystem.get(conf);
          while(true){
          FileStatus[] fsStatus =  fs.listStatus(new Path("/"));

          for(int i = 0; i < fsStatus.length; i++) {
              System.out.println(fsStatus[i].getPath().toString());
          }
        }
    }
    }

Or I followed examples but when I tried to turn NN1 while this client is running, I'm getting exception that NN1 isnt available anymore and application is shutting down. Can someone point me in right direction?
Thank you

Re: HA Hadoop core

jsensharma — Tue, 05 Dec 2017 18:15:10 GMT

@Ivan Majnaric

Your following property should be pointing to the NameService instead of the Individual NN host.

Incorrect code:

conf.set("fs.defaultFS", "hdfs://bigdata5.int.ch:8020");
conf.set("dfs.ha.namenodes.nameservice1", "nn1,nn2");

Should be something like following:

conf.set("fs.defaultFS", "hdfs://hdfscluster");
conf.set("dfs.ha.namenodes.hdfscluster", "nn1,nn2");

For more details please refer to: http://henning.kropponline.de/2016/11/27/sample-hdfs-ha-client/

Re: HA Hadoop core

majnam — Tue, 05 Dec 2017 18:45:47 GMT

Thank you very much sir. You solved my case 🙂