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DuckDB delta extension install races across parallel tests #6743
Description
Expected Behavior
The DuckDB offline integration suite should run reliably with 8 pytest-xdist workers on a fresh runner.
Current Behavior
DuckDBDelta tests intermittently fail while several workers auto-install the delta extension into the shared ~/.duckdb/extensions directory. The losing worker reports:
_duckdb.IOException: IO Error: Could not set lock on file ".../delta.duckdb_extension.tmp-...duckdb_extension.info": Conflicting lock is held in .../python3.10 (PID ...)
I found the same failure in 3 unrelated Linux CI runs:
- https://github.com/feast-dev/feast/actions/runs/31946521769
- https://github.com/feast-dev/feast/actions/runs/30604216643
- https://github.com/feast-dev/feast/actions/runs/30477658759
The failures affected 2 different DuckDBDelta tests, so this is not tied to one test's behavior.
Steps to reproduce
- Start with an empty DuckDB extension cache on Linux.
- Install the locked
duckdb-testsPixi environment. - Run
pixi run -e duckdb-tests test, which executes the offline integration suite withpytest -n 8. - Several workers may observe that
deltais not installed and attempt to install it into the same extension directory.
The race is intermittent. I could not reproduce the lock failure on Apple Silicon macOS, including 80 synchronized cold-cache extension loads, but the 3 GitHub-hosted Linux runs above provide independent positive reproductions.
Specifications
- Version: current
masterat f771ea4 - Platform: GitHub-hosted Linux,
linux_amd64 - Subsystem: DuckDB offline integration tests
- Locked dependencies: Python 3.10.20, DuckDB 1.5.4, Ibis 12.0.0, pytest-xdist 3.8.0
Possible Solution
Install delta once before starting the parallel test workers. For example, add a serial Pixi task dependency that runs:
python -c "import duckdb; duckdb.connect().install_extension('delta')"I validated this against a separate cold cache. A fresh Ibis connection reported delta as installed but not loaded, then load_extension("delta") changed only the loaded state. This avoids Ibis's per-worker INSTALL path. The full 8-worker Feast suite then passed with 84 tests passed and 5 skipped.
Worker-specific extension directories would also avoid contention, but would download and install the same extension once per worker.
Activity
larrysingleton007 commentedon Aug 16, 2026
Implementation plan
The 8 pytest workers can all decide the DuckDB
deltaextension is missing and race to install it into the same cache directory.I'll add a small Pixi task that installs
delta, then make the existing DuckDB integration test task depend on it. Pixi will complete that task before starting pytest, so workers only need to load the installed extension.The only source change should be
pyproject.toml. I'll verify the task graph, use a separate empty home directory to prove the extension is installed before pytest starts, and run the complete locked DuckDB integration task.larrysingleton007 commentedon Aug 16, 2026
Implementation is in #6744.
The DuckDB test task now depends on a serial
deltaextension install, so pytest workers start after the shared extension cache is populated.Validation used an empty DuckDB cache. Pixi completed the install task before pytest, a fresh connection saw
deltaas installed and not loaded, and the complete 8-worker suite passed with 84 tests passed and 5 skipped.fix: Preinstall DuckDB delta extension for tests
fix: Preinstall DuckDB delta extension for tests
chore(release): release 0.66.0
fix: Preinstall DuckDB delta extension for tests
chore(release): release 0.66.0