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From "Xu Zhang (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-72) Porting Pig unit tests to use MiniDFSCluster and MiniMRCluster on the local machine
Date Wed, 23 Jan 2008 23:28:34 GMT
Porting Pig unit tests to use MiniDFSCluster and MiniMRCluster on the local machine
-----------------------------------------------------------------------------------

                 Key: PIG-72
                 URL: https://issues.apache.org/jira/browse/PIG-72
             Project: Pig
          Issue Type: Test
          Components: tools
            Reporter: Xu Zhang


We have the need to port the Pig unit tests to use MiniDFSCluster and MiniMRCluster, so that
tests can be executed with the DFS and MR threads on the local machine.   This feature will
eliminate the need to set up a real distributed hadoop cluster before running the unit tests,
as everything will now be carried out with the (mini) cluster on the user's local machine.
 

One prerequisite for using this feature is a hadoop jar that has the class files for MiniDFSCluster,
MiniMRCluster and other supporting components.  I have been able to generate such a jar file
with a special target added by myself to hadoop's build.xml and have also logged a hadoop
jira to request this target be a permanent part of that build file.  If possible, we can just
replace hadoop15.jar with this jar file on the SVN source tree and then the users will never
need to worry about the availability of this jar file. Please find such a hadoop jar file
in the attachment.

To use the feature in unit tests, the user just need to call MiniClusterBuilder.buildCluster()
before a PigServer instance is created with the string "mapreduce" as the parameter to its
constructor.  Here is an example of how the MiniClusterBuilder is used in a test case class:

        public class TestWhatEver extends TestCase {
	        private String initString = "mapreduce";
	        private MiniClusterBuilder cluster = MiniClusterBuilder.buildCluster();
	
                @Test
                public void testGroupCountWithMultipleFields() throws Exception {
                        PigServer pig = new PigServer(initString);
                        // Do something with the pig server, such as registering and executing
Pig 
                        // queries. The queries will executed with the local cluster. 
                }
     
                // More test cases if needed
        }

To run the unit tests with the local cluster, under the top directory of the source tree,
issue the command "ant test". Notice that you do not need to specify the location of the hadoop-site.xml
file with the command line option "-Djunit.hadoop.conf=<dir>" anymore. 

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