[ZEPPELIN-2414] Memory leak under scoped mode of SparkInterpreter caused by inapproprately setting Thread.contextClassLoader

[hammertank]

What is this PR for?

Fix memory leak under scoped mode of SparkInterpreter which is caused by inapproprately setting Thread.contextClassLoader.

What type of PR is it?

Bug Fix

Todos

Rest Thread.contextClassLoader in Methods:

• - Wraps interpreters with ClassLoader with ClassLoaderInterpreter in RemoteInterpreterServer.createInterpreter

What is the Jira issue?

https://issues.apache.org/jira/browse/ZEPPELIN-2414

How should this be tested?

Questions:

• Does the licenses files need update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

[hammertank]

@jongyoul Ready to review. Please help. This PR is based on commits from #2262. Maybe this PR can wait until #2262 is merged.

[Leemoonsoo]

Thanks @hammertank for the contribution.

What do you think wrap interpreter using ClassLoaderInterpreter instead of modifying individual interpreter?

Interpreter is being instantiated from RemoteInterpreterServer, so this is place where ClassLoaderInterpreter can wrap Interpreter. Like Interpreter factory does

[hammertank]

@Leemoonsoo Changed the code as you suggested. But I find it difficult to write a testcase to validate the modification.

[Leemoonsoo]

#2262 has been merged. so now, could you try include commit only related to this contributions?

[hammertank]

@Leemoonsoo re-commit as required. Please review again.
Jenkins did not get the final travis-ci results successfully. Is there a way to trigger Jenkins to fetch again without a push?

[Leemoonsoo]

You can close/reopen the issue to trigger Jenkins

[hammertank]

Found "ClassNotFoundException" after applying this fix. This is caused by SparkContext using the first TranslatingClassLoader to deserialize TaskResult.
Sorry to say that I haven't figure out a solution yet. 😭
I'm quite busy with my work recently.