[HADOOP-4340] "hadoop jar" always returns exit code 0 (success) to the shell when jar throws a fatal exception

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.18.1, 0.19.0, 0.20.0
• Fix Version/s: 0.18.2

Environment

Ubuntu 8.04 Server, 7 Hadoop nodes, GNU bash, version 3.2.39(1)-release (i486-pc-linux-gnu)

• Hadoop Flags: Reviewed
• Assignee: Arun Murthy
• Reporter: David Litster
• Created: 03/Oct/08 22:40
• Updated: 08/Jul/09 17:06
• Resolved: 29/Oct/08 23:10

Description

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.

Please let me know what other information I can include about my setup

Thanks.

Issue Links

• relates to: MAPREDUCE-421 mapred pipes might return exit code 0 even when failing