[MAPREDUCE-7251] Present friendlier error for non-static main

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.9.2
• Labels: pull-request-available
• Assignee: Unassigned
• Reporter: Connor Taffe
• Created: 10/Dec/19 17:09
• Updated: 28/Jan/22 05:39

Description

When running a jar with hadoop jar, e.g. when submitting using gcloud dataproc jobs submit hadoop, a JAR with a non-static main gives a cryptic error message that could be clearer. The current error message in Hadoop 2.9.2 looks like:

Exception in thread "main" java.lang.NullPointerException
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:498)
  at org.apache.hadoop.util.RunJar.run(RunJar.java:244)
  at org.apache.hadoop.util.RunJar.main(RunJar.java:158)
  at com.google.cloud.hadoop.services.agent.job.shim.HadoopRunJarShim.main(HadoopRunJarShim.java:12)

Instead, it would be more helpful to show an error message like "Method main must be static: foo.bar.BazMR".

Issue Links

• links to: GitHub Pull Request #1751