java - Hbase client can't connect to remote Hbase server

Question

i have written a following hbase client class for remote server:

System.out.println("Hbase Demo Application ");

            // CONFIGURATION

                // ENSURE RUNNING
            try {
                HBaseConfiguration config = new HBaseConfiguration();
                config.clear();
                config.set("hbase.zookeeper.quorum", "192.168.15.20");
                config.set("hbase.zookeeper.property.clientPort","2181");
                config.set("hbase.master", "192.168.15.20:60000");
                //HBaseConfiguration config = HBaseConfiguration.create();
    //config.set("hbase.zookeeper.quorum", "localhost");  // Here we are running zookeeper locally
                HBaseAdmin.checkHBaseAvailable(config);


                System.out.println("HBase is running!");
            //  createTable(config);    
                //creating a new table
                HTable table = new HTable(config, "mytable");
                System.out.println("Table mytable obtained ");  
                addData(table);
            } catch (MasterNotRunningException e) {
                System.out.println("HBase is not running!");
                System.exit(1);
            }catch (Exception ce){ ce.printStackTrace();

it is throwing some exception:

Oct 17, 2011 1:43:54 PM org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation getMaster
INFO: getMaster attempt 0 of 1 failed; no more retrying.
java.net.ConnectException: Connection refused
    at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
    at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:567)
    at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
    at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:404)
    at org.apache.hadoop.hbase.ipc.HBaseClient$Connection.setupIOstreams(HBaseClient.java:328)
    at org.apache.hadoop.hbase.ipc.HBaseClient.getConnection(HBaseClient.java:883)
    at org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:750)
    at org.apache.hadoop.hbase.ipc.HBaseRPC$Invoker.invoke(HBaseRPC.java:257)
    at $Proxy4.getProtocolVersion(Unknown Source)
    at org.apache.hadoop.hbase.ipc.HBaseRPC.getProxy(HBaseRPC.java:419)
    at org.apache.hadoop.hbase.ipc.HBaseRPC.getProxy(HBaseRPC.java:393)
    at org.apache.hadoop.hbase.ipc.HBaseRPC.getProxy(HBaseRPC.java:444)
    at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getMaster(HConnectionManager.java:359)
    at org.apache.hadoop.hbase.client.HBaseAdmin.<init>(HBaseAdmin.java:89)
    at org.apache.hadoop.hbase.client.HBaseAdmin.checkHBaseAvailable(HBaseAdmin.java:1215)
    at com.ifkaar.hbase.HBaseDemo.main(HBaseDemo.java:31)
HBase is not running!

can you tell me why is it throwing an exception, what is wrong with code and how to solve it.

Answer 1

This problem is occuring due to your HBase server's hosts file.
You just need to edit you HBase server's /etc/hosts file.
Remove the localhost entry from that file and put the localhost entry in front of HBase server IP.

For example, your HBase server's /etc/hosts files seems like this:

127.0.0.1 localhost
192.166.66.66 xyz.hbase.com hbase

You have to change it like this by removing localhost:

# 127.0.0.1 localhost # line commented out
192.166.66.66 xyz.hbase.com hbase localhost # note: localhost added here

This is because when remote machine asks hbase server machine where HMaster is running, it tells that it is running on localhost.
So if the entry is 127.0.0.1 then HBase server returns this address and remote machine start to find HMaster on its own machine (locally).
When we change that with the HBase Server IP then everything works fine :)