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https://issues.apache.org/jira/browse/SPARK-24918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16595020#comment-16595020
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Sean Owen commented on SPARK-24918:
-----------------------------------
Wait, why doesn't a static init "run everywhere"? is "everywhere" the same as
"on every executor that will run a task"? and why would an executor be able to
init without touching a static initializer that the user code touches? Yes you
just call it somewhere in any task that needs the init. There's no overhead in
checking the init and initting if not. Therein is the issue, I suppose: you
have to put some reference to a class or method in every task. The upshot is it
requires no additional mechanism or reasoning about what thread runs what.
> Executor Plugin API
> -------------------
>
> Key: SPARK-24918
> URL: https://issues.apache.org/jira/browse/SPARK-24918
> Project: Spark
> Issue Type: New Feature
> Components: Spark Core
> Affects Versions: 2.4.0
> Reporter: Imran Rashid
> Priority: Major
> Labels: SPIP, memory-analysis
>
> It would be nice if we could specify an arbitrary class to run within each
> executor for debugging and instrumentation. Its hard to do this currently
> because:
> a) you have no idea when executors will come and go with DynamicAllocation,
> so don't have a chance to run custom code before the first task
> b) even with static allocation, you'd have to change the code of your spark
> app itself to run a special task to "install" the plugin, which is often
> tough in production cases when those maintaining regularly running
> applications might not even know how to make changes to the application.
> For example, https://github.com/squito/spark-memory could be used in a
> debugging context to understand memory use, just by re-running an application
> with extra command line arguments (as opposed to rebuilding spark).
> I think one tricky part here is just deciding the api, and how its versioned.
> Does it just get created when the executor starts, and thats it? Or does it
> get more specific events, like task start, task end, etc? Would we ever add
> more events? It should definitely be a {{DeveloperApi}}, so breaking
> compatibility would be allowed ... but still should be avoided. We could
> create a base class that has no-op implementations, or explicitly version
> everything.
> Note that this is not needed in the driver as we already have SparkListeners
> (even if you don't care about the SparkListenerEvents and just want to
> inspect objects in the JVM, its still good enough).
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