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From "David Litster (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-4340) "hadoop jar" always returns exit code 0 (sucess) to the shell when jar throws a fatal exception
Date Fri, 03 Oct 2008 22:41:44 GMT
"hadoop jar" always returns exit code 0 (sucess) to the shell when jar throws a fatal exception

------------------------------------------------------------------------------------------------

                 Key: HADOOP-4340
                 URL: https://issues.apache.org/jira/browse/HADOOP-4340
             Project: Hadoop Core
          Issue Type: Bug
    Affects Versions: 0.18.1
         Environment: Ubuntu 8.04 Server, 7 Hadoop nodes,  
            Reporter: David Litster


Running "hadoop jar" always returns 0 (success) when the jar dies with a stack trace.  As
an example, run these commands:

/usr/local/hadoop/bin/hadoop jar /usr/local/hadoop/hadoop-0.18.1-examples.jar pi 10 10 2>&1;
echo $?
exits with 0

/usr/local/hadoop/bin/hadoop jar /usr/local/hadoop/hadoop-0.18.1-examples.jar pi 2>&1;
echo $?
exits with 255

/usr/local/hadoop/bin/hadoop jar /usr/local/hadoop/hadoop-0.18.1-examples.jar  2>&1;
echo $?
exits with 0 

This seems to be expected behavior.  However, running:

/usr/local/hadoop/bin/hadoop jar /usr/local/hadoop/hadoop-0.18.1-examples.jar pi 10 badparam
2>&1; echo $?
java.lang.NumberFormatException: For input string: "badparam"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
        at java.lang.Long.parseLong(Long.java:403)
        at java.lang.Long.parseLong(Long.java:461)
        at org.apache.hadoop.examples.PiEstimator.run(PiEstimator.java:241)
        at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
        at org.apache.hadoop.examples.PiEstimator.main(PiEstimator.java:252)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:68)
        at org.apache.hadoop.util.ProgramDriver.driver(ProgramDriver.java:139)
        at org.apache.hadoop.examples.ExampleDriver.main(ExampleDriver.java:53)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.util.RunJar.main(RunJar.java:155)
        at org.apache.hadoop.mapred.JobShell.run(JobShell.java:54)
        at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
        at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:79)
        at org.apache.hadoop.mapred.JobShell.main(JobShell.java:68)
exits with 0.

In my opinion, if a jar throws an exception that kills the program being run, and the developer
doesn't catch the exception and do a sane exit with a exit code, hadoop should at least exit
with a non-zero exit code.

As another example, while running a main class that exits with an exit code of 201, Hadoop
will preserve the correct exit code:

    public static void main(String[] args) throws Exception {
    System.exit(201);
  }

But when deliberately creating a null pointer exception, Hadoop exits with 0.

  public static void main(String[] args) throws Exception {
	Object o = null;
	o.toString();
    System.exit(201);
  }

This behaviour makes it very difficult, if not impossible, to use Hadoop programatically with
tools such as HOD or non-Java data processing frameworks, since if a jar crashes with an unhandled
exception, Hadoop doesn't inform the calling program in a well-bahaved way (polling stderr
for output is not a very good way to detect application failure).     

I'm not a Java programmer, so I don't know what the best code to signal failure would be.

Thanks. 





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