Monitor's ParallelMatcher and PartitionMatcher catch only IOException per query: one registered query that throws an unchecked exception at match time makes Monitor.match throw and lose every match of the batch, and ParallelMatcher blocks forever once all its workers have died
Finding LFV-326Area: monitor / concurrent candidate matchers (ParallelMatcher, PartitionMatcher)Priority: lowImpact: hangNovelty: new
AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.
What it shows
You register queries in a Monitor and match documents with ParallelMatcher or PartitionMatcher, which the package docs offer as a performance option, and one registered query throws an unchecked exception at match time, for example an IntPoint range query meeting a field indexed as LongPoint (IllegalArgumentException). You expect what the default serial matcher does: that query is reported in getErrors() and every other match is returned. Instead the worker threads catch only IOException, so Monitor.match throws RuntimeException('Interrupted during match') and the whole batch's matches are lost, and with ParallelMatcher, once every worker has died, the caller blocks forever in LinkedBlockingQueue.put (executed: 4 threads, one registered query with 4 failing disjuncts plus 1,100 other queries, still blocked after 20 s, 77 interrupts to stop).
The test shows that with PartitionMatcher, a registered query that throws an unchecked exception at match time (an IntPoint query on a field indexed as LongPoint) makes Monitor.match throw, and the other query's match is lost.
Expected vs actual
Expected 1 match ("long") plus an error reported for "int" in getErrors(), as the serial matcher returns; actual: RuntimeException: Interrupted during match (caused by the IllegalArgumentException), with -ea and -da.
Files
Run it
- Tested on Lucene main e1faeba08bde (2026-11-02): still reproduces.
- Tested on Lucene main 645d4fe14a20 (2026-10-28): reproduced.
- Recorded outcome of run 1 on Lucene main 645d4fe14a20: 1 test(s) run, 1 failed.
- How to read the outcome: a failing test is the finding reproducing (the failure message states expected against actual).
- Seeds: a rerun with the same seed replays the same random choices. Assertions off (-da -dsa -Dtests.asserts=false) is the production-like setting.
# Lucene checkout at the tested commit, built with: ./gradlew --no-daemon assemble (JDK 25)
LUCENE=/path/to/lucene; V=12.0.0-SNAPSHOT
CP=$LUCENE/lucene/core/build/libs/lucene-core-$V.jar
CP=$CP:$LUCENE/lucene/codecs/build/libs/lucene-codecs-$V.jar
CP=$CP:$LUCENE/lucene/test-framework/build/libs/lucene-test-framework-$V.jar
CP=$CP:$LUCENE/lucene/analysis/common/build/libs/lucene-analysis-common-$V.jar
CP=$CP:$LUCENE/lucene/memory/build/libs/lucene-memory-$V.jar
CP=$CP:$LUCENE/lucene/monitor/build/libs/lucene-monitor-$V.jar
CP=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar # test-framework dependencies (Maven Central)
CP=$CP:junit-platform-console-standalone-6.1.3.jar # JUnit Platform console launcher (Maven Central)
javac -d classes -cp "$CP" $(find src -name '*.java')
# run 1: assertions on, seed DEADBEEF
java -ea -esa --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -Dtests.seed=DEADBEEF \
-cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
execute --select-class org.apache.lucene.monitor.TestPartitionMatcherUncheckedQueryErrorGradle alternative: copy the test into the matching module's src/test/ tree of the checkout and run ./gradlew -p lucene/<module> test --tests <class> -Ptests.seed=<seed> (add -Ptests.asserts=false for a run without assertions).
Feedback
Open an issue in lucene-ai-bug-hunt. Please do not open issues or pull requests in apache/lucene about this finding unless a Lucene committer agrees it should be filed.
Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.