MONGOID-5823 Use proper thread-local variables instead of fiber-local variables #5891
Conversation
This file contains 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
Using fiber-local variables instead of thread-local variables has the potential to introduce difficult bugs when Mongoid's internal state is not visible to Fiber-wrapped cascading callbacks.
comandeo-mongo
approved these changes
Oct 24, 2024
jamis
added a commit
to jamis/mongoid
that referenced
this pull request
Oct 24, 2024
… variables (mongodb#5891) * MONGOID-5823 Use proper thread-local variables Using fiber-local variables instead of thread-local variables has the potential to introduce difficult bugs when Mongoid's internal state is not visible to Fiber-wrapped cascading callbacks. * remove cruft from an earlier experient * *grumble* rubocop *grumble* * fix test failures * compensate for jruby
jamis
added a commit
that referenced
this pull request
Oct 25, 2024
… variables (#5891) (#5896) * MONGOID-5823 Use proper thread-local variables Using fiber-local variables instead of thread-local variables has the potential to introduce difficult bugs when Mongoid's internal state is not visible to Fiber-wrapped cascading callbacks. * remove cruft from an earlier experient * *grumble* rubocop *grumble* * fix test failures * compensate for jruby
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Outdated suggestions cannot be applied.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.
MONGOID-5688 introduced a new way of processing cascading callbacks on embedded children, using Fibers to linearize the recursive calls. This proved very effective in avoiding
SystemStackErrorexceptions caused by large numbers of embedded documents.However, it turns out that
Thread#[]andThread#[]=get and set fiber-local variables, and not thread-local variables. Mongoid was using these methods quite a bit to set and manage its own internal state, which meant that any cascading callback on embedded children would be executed in a context that lacked all of Mongoid's state from the parent thread.This PR fixes this issue by changing Mongoid's state handling routines (
Mongoid::Threaded) to use actual thread-local storage (Thread#thread_variable_getandThread#thread_variable_set) instead of the fiber-local variables.