Enable WAL mode and fix TOCTOU race in migrations to prevent database locking errors - #1572
Open
ikatyal2110 wants to merge 1 commit into
Open
Enable WAL mode and fix TOCTOU race in migrations to prevent database locking errors#1572ikatyal2110 wants to merge 1 commit into
ikatyal2110 wants to merge 1 commit into
Conversation
… errors When multiple llm processes start simultaneously they all call migrate() which previously used a check-then-create pattern for the migrations table (a TOCTOU race) and left the database in the default rollback-journal mode where any exclusive write lock blocks all readers. Switching to WAL mode eliminates the reader-blocks-writer problem, and using if_not_exists=True removes the race. Fixes simonw#789
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
When multiple
llmprocesses start at the same time (e.g. viaxargs -P), they each callmigrate(), which left the database in the default rollback-journal mode where any exclusive write lock blocks all readers, and used a check-then-create pattern for_llm_migrationsthat creates a TOCTOU race. The fix enables WAL mode for file-backed databases so concurrent reads are never blocked by a writer, and usesCREATE TABLE IF NOT EXISTS(viaif_not_exists=True) to atomically create the migrations table, eliminating the race. Regression tests confirm WAL mode is set after migration and that callingensure_migrations_tabletwice is safe. Fixes #789Generated by Claude Code