Formal models and scripts: reader-open-leaf-sorter-failure-leaks

Tools: TLA+/TLC

These are the working models and scripts this part of the hunt used. Some encode the code as it is (a counterexample is the expected result), others a fixed or correct variant; read the header comment of each file. Paths inside them were replaced by placeholders such as $LUCENE (a Lucene checkout) and $WORK.

Findings

• A failed NRT reader open (DirectoryReader.open(IndexWriter), openIfChanged over the writer, or a SearcherManager/ReaderManager refresh) whose IndexWriterConfig leaf sorter throws never releases the IndexFileDeleter reference it took, so the still-open writer keeps every segment file of that point in time on disk for the rest of its life (finding LFV-1067; repro · finding page)

Files

• nrt-open-leaf-sorter-failure-keeps-deleter-references/model/NrtOpen.tla (used for LFV-1067)

How to run

• TLA+ with TLC: java -cp tla2tools.jar tlc2.TLC -config <Model>.cfg <Model>.tla (a counterexample trace is the finding when the model encodes the current code).

Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.