DirectoryTaxonomyWriter.close() skips its own cleanup when its commit fails: after an I/O error that closes the internal IndexWriter every close() throws and the writer's near-real-time reader keeps its segment files open, and after an fsync error inside close() the IndexWriter and the taxonomy write lock stay held until close() is retried or rollback() is called (every release since 5.0.0)

Finding LFV-555Area: facet / taxonomy writer: DirectoryTaxonomyWriter.close() (failure cleanup)Priority: lowImpact: minorNovelty: new

Finding page for LFV-555

AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

You add categories to a DirectoryTaxonomyWriter, a commit fails with an I/O error (for example a full disk while the new segment is written), and you then call close(), whose javadoc says it 'Frees used resources as well as closes the underlying IndexWriter'. You expect close() to release the writer's resources even when it throws, as IndexWriter.close() has done since LUCENE-4246. Instead close() is 'commit(); indexWriter.close(); doClose();' with no try/finally, so it throws AlreadyClosedException from its own commit() on every call and never closes its internal near-real-time reader, whose segment file stays open; when the error is an fsync inside close(), the internal IndexWriter and the taxonomy's write lock also stay held until close() is retried or rollback() is called.

The test shows that after a commit fails with an I/O error (an aborting segment-write error that closes the internal IndexWriter), DirectoryTaxonomyWriter.close() throws from its own commit() and never closes its near-real-time reader.

Expected vs actual

Expected: close() frees the reader (as its javadoc says), so MockDirectoryWrapper.close() succeeds. Actual: MockDirectoryWrapper: cannot close: there are still 1 open files: {_0.cfs=1} (-ea and -da).

Files

Run it

# 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/facet/build/libs/lucene-facet-$V.jar
CP=$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.facet.taxonomy.directory.TestDirectoryTaxonomyWriterCloseAfterFailure

The module(s) facet also need their third-party runtime jars; ./gradlew -p lucene/<module> dependencies lists them.

Gradle 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.