Question

I have a jar file with predefined entry point in its manifest file. And it can successfully be executed.

hadoop jar hadoop-test-1.0.2.jar -write -nrFiles 1 -fileSize 10
TestDFSIO.0.0.4
12/06/11 21:35:09 INFO fs.TestDFSIO: nrFiles = 1
12/06/11 21:35:09 INFO fs.TestDFSIO: fileSize (MB) = 10
12/06/11 21:35:09 INFO fs.TestDFSIO: bufferSize = 1000000
12/06/11 21:35:09 INFO fs.TestDFSIO: creating control file: 10 mega bytes, 1 files
12/06/11 21:35:09 INFO fs.TestDFSIO: created control files for: 1 files
12/06/11 21:35:10 INFO mapred.FileInputFormat: Total input paths to process : 1
12/06/11 21:35:10 INFO mapred.JobClient: Running job: job_201206110904_0029
12/06/11 21:35:11 INFO mapred.JobClient:  map 0% reduce 0%
12/06/11 21:35:25 INFO mapred.JobClient:  map 100% reduce 0%
12/06/11 21:35:37 INFO mapred.JobClient:  map 100% reduce 100%
...

Now my concern is how to execute the jar without the options.
I mean I just want to invoke:

hadoop jar hadoop-test-1.0.2.jar

I need to somehow define the arguments like "-write -nrFiles 1 -fileSize 10" inside the jar file. But how?

How can I define it in the manifest file? I know that I can generate a class of my own which then initiates the test class with these parameters. But is there any other workaround?

Surprisingly: Defined a class which calls the required class with the args.

Execution try:

hadoop jar hadoop-test-1.0.2.jar 
RunJar jarFile [mainClass] args...

With the name of the class as arg, it works!

hadoop jar hadoop-test-1.0.2.jar Start
TestDFSIO.0.0.4
12/06/12 01:05:11 INFO fs.TestDFSIO: nrFiles = 10
12/06/12 01:05:11 INFO fs.TestDFSIO: fileSize (MB) = 1000
12/06/12 01:05:11 INFO fs.TestDFSIO: bufferSize = 1000000
12/06/12 01:05:11 INFO fs.TestDFSIO: creating control file: 1000 mega bytes, 10 files
12/06/12 01:05:11 INFO fs.TestDFSIO: created control files for: 10 files
12/06/12 01:05:11 INFO mapred.FileInputFormat: Total input paths to process : 10
12/06/12 01:05:12 INFO mapred.JobClient: Running job: job_201206110904_0033
...

Content of my Manifest:

Manifest-Version: 1.0
Ant-Version: Apache Ant 1.7.1
Created-By: 20.1-b02 (Sun Microsystems Inc.)
Main-Class: Start

Name: org/apache/hadoop
Implementation-Title: Hadoop
Implementation-Version: 1.0.2
Implementation-Vendor: Apache

The content of the Start.java:

import org.apache.hadoop.fs.TestDFSIO;
public class Start {

        public static void main(String[] args) throws Exception{
                String [] myargs  = {"-write","-nrFiles","10","-fileSize","1000"};

                TestDFSIO.main(myargs);

        }
}

What am I doing wrong? Why am I not able to execute Start using the jar file without args to execute the original class TestDFIO? Thx!

Answer 1

Nope. You can either create a new main method or get the arguments from somewhere else, for example, a config file, environment variables, etc.

You could also just write a wrapping shell script that does that part.

Without knowing why you need to do this it’s more difficult to provide actionable ideas.