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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