Fix: Prevent Flask hot reload from hanging due to early thread startup #7966
Conversation
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
Fix: Prevent Flask hot reload from hanging due to early thread startup
dosubot
bot
added
size:S
4 tasks
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
Fix: Prevent Flask hot reload from hanging due to early thread startup
What problem does this PR solve?
When running the Flask server with
use_reloader=True(enabled during debug mode), modifying a Python source file would trigger a reload detection (Detected change in ...), but the application would hang instead of restarting cleanly.This was caused by the
update_progressbackground thread being started too early, often within the main module scope.This issue was reported in #7498.
Type of change
Summary of changes:
update_progresslaunch in athreading.Timerwith delay to avoid premature thread execution.daemon=Trueto avoid blocking process exit.WERKZEUG_RUN_MAINenvironment check to ensure background threads only run in the reloader child process (the actual Flask app).debug=False).