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Posted to issues@lucene.apache.org by "Paweł Bugalski (Jira)" <ji...@apache.org> on 2021/02/19 12:45:00 UTC

[jira] [Updated] (LUCENE-9791) Monitor (aka Luwak) has concurrency issues related to BytesRefHash#find

     [ https://issues.apache.org/jira/browse/LUCENE-9791?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Paweł Bugalski updated LUCENE-9791:
-----------------------------------
    Attachment: LUCENE-9791.patch

> Monitor (aka Luwak) has concurrency issues related to BytesRefHash#find
> -----------------------------------------------------------------------
>
>                 Key: LUCENE-9791
>                 URL: https://issues.apache.org/jira/browse/LUCENE-9791
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: core/other
>    Affects Versions: master (9.0), 8.7, 8.8
>            Reporter: Paweł Bugalski
>            Priority: Major
>         Attachments: LUCENE-9791.patch
>
>
> _org.apache.lucene.monitor.Monitor_ can sometimes *NOT* match a document that should be matched by one of registered queries if match operations are run concurrently from multiple threads. 
> This is because sometimes in a concurrent environment _TermFilteredPresearcher_ might not select a query that could later on match one of documents being matched.
> Internally _TermFilteredPresearcher_ is using a term acceptor: an instance of _org.apache.lucene.monitor.QueryIndex.QueryTermFilter_. _QueryTermFilter_ is correctly initialized under lock and its internal state (a map of _org.apache.lucene.util.BytesRefHash_ instances) is correctly published. Later one when those instances are used concurrently a problem with _org.apache.lucene.util.BytesRefHash#find_ is triggered since it is not thread safe.
> _org.apache.lucene.util.BytesRefHash#find_ internally is using a private _org.apache.lucene.util.BytesRefHash#equals_ method, which is using an instance field _scratch1_ as a temporary buffer to compare its _ByteRef_ parameter with contents of _ByteBlockPool_. This is not thread safe and can cause incorrect answers as well as _ArrayOutOfBoundException_. 
> __
>  



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