[ZEPPELIN-2216] general solution to precode. refactoring jdbc precode

[tinkoff-dwh]

What is this PR for?

General solution to execute precode. Refactoring jdbc precode using general solution. Task contains to subtasks: executeAfterOpen, executeBeforeClose. executeBeforeClose not done because we need the context so there is a solution only for executeAfterOpen.

What type of PR is it?

Feature | Refactoring

What is the Jira issue?

https://issues.apache.org/jira/browse/ZEPPELIN-2216

How should this be tested?

1. Add parameter zeppelin.PySparkInterpreter.precode someVar='text'
2. Execute

%pyspark
print(someVar)

Questions:

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

[tinkoff-dwh]

ready to review

[tinkoff-dwh]

@Leemoonsoo
prevous discussion #2096

[Leemoonsoo]

Let me take a look in this weekend!

[Leemoonsoo]

Shouldn't RemoteInterpreterServer.open() also call executePrecode()?

[tinkoff-dwh]

it must be called once per instance of the interprete

[tinkoff-dwh]

@Leemoonsoo
works same as the previous jdbc precode.
case:
user: some_user
JDBC interpreter (per user)

1. there is precode CREATE table IF NOT EXISTS tbl_#{user}
2. user executes insert into tbm_some_user ...
   • execute precode
   • execute paragraph text
3. user executes select *from tbm_some_user
   • execute paragraph text

Spark

1. there is precode var someConst = 12 ...
2. User executes var result = 1 + someConst
   • execute precode
   • execute paragraph text
3. User executes var

result2 = 2 + someConts
print(result2)

• execute only paragraph text

[Leemoonsoo]

Thanks for explain.

Currently, unittest https://github.com/apache/zeppelin/pull/2221/files#diff-9c5e6fbaa5b23bc0192b4fedc12b2680R445 executes jdbcInterpreter.executePrecode(interpreterContext); manually after open().

Shell we have other unittest that does not call executePrecode() manually? so lazy.executePrecode in InterpreterServer can be verified.

zeppelin-interpreter/src/test/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreterTest.java is one place the unittest actually creates RemoteInterpreter process and test against it. This place might be the place you can locate test for this feature.

[tinkoff-dwh]

@Leemoonsoo
fix it, if I understand correctly your comment

ci green https://travis-ci.org/tinkoff-dwh/zeppelin/builds/225094590

[Leemoonsoo]

LGTM and merge to master if no further discussions.