[jira] [Commented] (TINKERPOP-2126) toString() methods not thread-safe

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TINKERPOP-2126?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16750434#comment-16750434 ] 

ASF GitHub Bot commented on TINKERPOP-2126:
-------------------------------------------

dkuppitz commented on pull request #1044: TINKERPOP-2126 Fixed concurrency issue in `ObjectWritable::toString()`.
URL: https://github.com/apache/tinkerpop/pull/1044
 
 
   https://issues.apache.org/jira/browse/TINKERPOP-2126
   
   So, apparently, Spark 2.4.0 has some background logging going on, where it takes objects out of memory and dumps their `toString()` into the log. I don't think we can control when Spark is going to do that, so we have to work around it by making our `toString()` methods thread-safe or handle each `ConcurrentModificationException`. Guaranteeing thread-safety was easy for `TraverserSet` but turned out to be tricky (impossible?) for `ObjectWritable` as it's totally unclear where the objects are coming from and/or where they get modified while Spark is trying to log them.
   
   I don't think we can make any arbitrary object thread-safe, but we can easily catch the `ConcurrentModificationException` and retry until we succeed. `while (true)` looks a bit scary, but I don't think that this can ever become an infinite loop.
   
   `docker/build.sh -t -i -n` passed (as well as the external provider tests that consistently triggered the concurrency exceptions).
   
   VOTE +1
 
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> toString() methods not thread-safe
> ----------------------------------
>
>                 Key: TINKERPOP-2126
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2126
>             Project: TinkerPop
>          Issue Type: Bug
>          Components: process
>    Affects Versions: 3.3.5
>            Reporter: Daniel Kuppitz
>            Assignee: Daniel Kuppitz
>            Priority: Major
>             Fix For: 3.3.6, 3.4.1
>
>
> {{TraverserSet::toString()}} is not thread-safe as it uses an iterator on the internal map, which could concurrently be modified (most likely in OLAP environments).



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