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:
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-tests Pixi environment.
- Run pixi run -e duckdb-tests test, which executes the offline integration suite with pytest -n 8.
- Several workers may observe that delta is 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 master at 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.
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:
I found the same failure in 3 unrelated Linux CI runs:
The failures affected 2 different DuckDBDelta tests, so this is not tied to one test's behavior.
Steps to reproduce
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
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.