Paweł Bugalski created LUCENE-9791:
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Summary: 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: 8.8, 8.7, master (9.0)
Reporter: Paweł Bugalski
_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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