Add test for HTTP2 CONNECT termination #3655
Merged
+76
−0
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
howardjohn
added a commit
to howardjohn/h2
that referenced
this pull request
May 1, 2024
See hyperium/hyper#3652. What I have found is the final reference to a stream being dropped after the `maybe_close_connection_if_no_streams` but before the `inner.poll()` completes can lead to the connection dangling forever without any forward progress. No streams/references are alive, but the connection is not complete and never wakes up again. This seems like a classic TOCTOU race condition. In this fix, I check again at the end of poll and if this state is detected, wake up the task again. Wth the test in hyperium/hyper#3655, on my machine, it fails about 5% of the time: ``` 1876 runs so far, 100 failures (94.94% pass rate). 95.197349ms avg, 1.097347435s max, 5.398457ms min ``` With that PR, this test is 100% reliable ``` 64010 runs so far, 0 failures (100.00% pass rate). 44.484057ms avg, 121.454709ms max, 1.872657ms min ``` Note: we also have reproduced this using `h2` directly outside of `hyper`, which is what gives me confidence this issue lies in `h2` and not `hyper`.
This was referenced May 1, 2024
seanmonstar
pushed a commit
to hyperium/h2
that referenced
this pull request
May 2, 2024
See hyperium/hyper#3652. What I have found is the final reference to a stream being dropped after the `maybe_close_connection_if_no_streams` but before the `inner.poll()` completes can lead to the connection dangling forever without any forward progress. No streams/references are alive, but the connection is not complete and never wakes up again. This seems like a classic TOCTOU race condition. In this fix, I check again at the end of poll and if this state is detected, wake up the task again. Wth the test in hyperium/hyper#3655, on my machine, it fails about 5% of the time: ``` 1876 runs so far, 100 failures (94.94% pass rate). 95.197349ms avg, 1.097347435s max, 5.398457ms min ``` With that PR, this test is 100% reliable ``` 64010 runs so far, 0 failures (100.00% pass rate). 44.484057ms avg, 121.454709ms max, 1.872657ms min ``` Note: we also have reproduced this using `h2` directly outside of `hyper`, which is what gives me confidence this issue lies in `h2` and not `hyper`.
seanmonstar
approved these changes
May 3, 2024
|
Thank you! I was waiting to release |
|
Ah makes sense. Thanks! |
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.
For #3652.
In #3647, I thought I tracked down the root cause of #3652. However, with the help of @seanmonstar in #3652 (comment) I realized that this was too forcefully terminating the connection even if things other than SendRequest were still alive. I also realized the original test case I wrote was just wrong and failed to properly reproduce the issue.
This adds a test that properly reproduces the issue. On my machine, it fails about 5% of the time:
With further investigation, I believe this bug actually originates in
h2itself. hyperium/h2#772. With that PR, this test is 100% reliable