fix(python): commit read-only sessions to avoid spurious rollbacks#408
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fix(python): commit read-only sessions to avoid spurious rollbacks#408
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Every GET request opened an implicit PostgreSQL transaction that was rolled back when the session closed, generating ~200/s rollbacks visible in transaction count metrics during benchmarks. Wrapping the session yield in try/commit/except/rollback ensures: - Read-only transactions are committed (no-op for data, counts as commit in pg metrics instead of rollback) - Write operations that already committed inside the repository have no active transaction left, so the outer commit is a no-op - Exceptions still trigger an explicit rollback and re-raise Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Pull request overview
This pull request fixes an issue where read-only database operations (GET requests) were being rolled back instead of committed, causing spurious rollback metrics during benchmarking (~200/s rollbacks vs ~20/s commits). The fix wraps the session yield in a try/commit/except/rollback pattern so that all successful transactions, including read-only ones, are properly committed.
Changes:
- Modified the
get_sessionmethod inDatabaseManagerto explicitly commit successful transactions and rollback on exceptions - This change affects all database operations routed through FastAPI's dependency injection system
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Summary
GETrequest opened an implicit PostgreSQL transaction that was rolled back when the SQLAlchemy session closed (viaasync with session_factory() as session→session.close()→ implicit rollback)yieldintry/commit/except/rollbackso read-only transactions are committed rather than rolled backHow it works
GET /v1/lampsGET /v1/lamps/{id}POST /v1/lampsPUT /v1/lamps/{id}DELETE /v1/lamps/{id}Note: the
create()missing-commit bug was separately fixed in #407.Test plan
cd src/python && poetry run pytest🤖 Generated with Claude Code