[jira] [Created] (NIFI-3406) Multiple Improvements needed to ExecuteScript ScriptEngines configuration/information

["Joseph Percivall (JIRA)" <ji...@apache.org>]

Joseph Percivall created NIFI-3406:
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             Summary: Multiple Improvements needed to ExecuteScript ScriptEngines configuration/information
                 Key: NIFI-3406
                 URL: https://issues.apache.org/jira/browse/NIFI-3406
             Project: Apache NiFi
          Issue Type: Improvement
    Affects Versions: 1.1.1
            Reporter: Joseph Percivall
            Priority: Blocker


The issue prompting this is that JRuby's default configuration uses a Singleton scope[1]. So all threads will see the same runtime and variables. This means if a FlowFile is currently running within the body of a script, and a new one comes in, the first thread will use the new variables (session, flowfile, etc.). This is obviously a problem and can lead "flowfile not known in this session" and livelocks in the FF repo due to multiple sessions updating the same flowfile[2].

ExecuteScript needs to 
   1: give more information about the script engine being run
   2: provide more configuration options for the script engine it self
   3: warn the user about the nuances of script engines and how they are not maintained by Apache NiFi so may not follow our best practices.

[1] https://github.com/jruby/jruby/blob/master/core/src/main/java/org/jruby/embed/ScriptingContainer.java#L198

Specifically the line: "However, the default, singleton local context scope behave slightly different. If Ruby runtime has been already instantiated by another ScriptingContainer, application, etc, the same runtime will be used."
[2] https://github.com/JPercivall/nifi/blob/1be08714731f01347ac1f98e18047fe7d9ab8afd/nifi-commons/nifi-write-ahead-log/src/main/java/org/wali/MinimalLockingWriteAheadLog.java#L69-L69



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