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https://issues.apache.org/jira/browse/TOREE-374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15856880#comment-15856880
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Jakob Odersky commented on TOREE-374:
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Thanks for the reproduction steps, [~dtaieb].
The reason why results aren't garbage collected is due to the way the Scala
REPL represents evaluated expressions. This is true for both in the standard
object-wrapped repl as well as the class based one used by Toree.
Unfortunately I can't think of an easy fix that we could quickly get into
upstream. How severe is this bug in a typical use-case? Are cells reevaluated
enough without a kernel restart for it to become a problem?
[~mariusvniekerk] do you know if/how zeppelin has worked around this?
> Variables declared on the Notebook are not garbage collected
> ------------------------------------------------------------
>
> Key: TOREE-374
> URL: https://issues.apache.org/jira/browse/TOREE-374
> Project: TOREE
> Issue Type: Bug
> Affects Versions: 0.1.0
> Reporter: David Taieb
>
> I'm not sure if it's a bug or a limitation of the underlying scala REPL.
> As part of supporting PixieDust (https://github.com/ibm-cds-labs/pixiedust)
> auto-visualization feature within Scala gateway, I have implemented a weak
> hashmap that tracks objects declared on the Scala REPL. However, I have found
> that objects are not correctly gc'ed when the object is declared in a cell
> with a val or var keyword and then the cell is ran again. One would expect
> that the original object has no more references and should be gc'ed but it's
> not.
> However, when the object is declare with var keyword and then set to null in
> another cell, then it is correctly gc'ed.
> I'm concerned that users who run the same cell multiple times would
> unwittingly have memory leaks which can eventually lead to OOM errors.
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