fix: TimeoutTicker returns wrong value/timeout pair when timeouts are… #67
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… scheduled at ~approximately the same time (backport cometbft#3092) (cometbft#3107) cometbft#3091 The problem is we have an edge case where we should drain the timer channel, but we "let it slide" in certain race conditions when two timeouts are scheduled near each other. This means we can have unsafe timeout behavior as demonstrated in the github issue, and likely more spots in consensus. Notice that aside from NewTimer and OnStop, all timer accesses are from the same thread. In NewTimer we can block until the timer is drained (very quickly up to goroutine scheduling). In OnStop we don't need to guarantee draining before the method ends, we can just launch something into the channel that will kill it. In the main timer goroutine, we can safely maintain this "timerActive" variable, and force drain when its active. This removes the edge case. The test I created does fail on main. --- #### PR checklist - [X] Tests written/updated - [x] Changelog entry added in `.changelog` (we use [unclog](https://github.com/informalsystems/unclog) to manage our changelog) - [x] Updated relevant documentation (`docs/` or `spec/`) and code comments - [X] Title follows the [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) spec <hr>This is an automatic backport of pull request cometbft#3092 done by [Mergify](https://mergify.com). --------- Co-authored-by: Dev Ojha <[email protected]> Co-authored-by: Sergio Mena <[email protected]> Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
ValarDragon
approved these changes
May 23, 2024
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… scheduled at ~approximately the same time (backport cometbft#3092) (cometbft#3107)
cometbft#3091
The problem is we have an edge case where we should drain the timer channel, but we "let it slide" in certain race conditions when two timeouts are scheduled near each other. This means we can have unsafe timeout behavior as demonstrated in the github issue, and likely more spots in consensus.
Notice that aside from NewTimer and OnStop, all timer accesses are from the same thread. In NewTimer we can block until the timer is drained (very quickly up to goroutine scheduling). In OnStop we don't need to guarantee draining before the method ends, we can just launch something into the channel that will kill it.
In the main timer goroutine, we can safely maintain this "timerActive" variable, and force drain when its active. This removes the edge case.
The test I created does fail on main.
PR checklist
.changelog(we use unclog to manage our changelog)docs/orspec/) and code commentsThis is an automatic backport of pull request fix: TimeoutTicker returns wrong value/timeout pair when timeouts are scheduled at ~approximately the same time cometbft/cometbft#3092 done by Mergify.
PR checklist
.changelog(we use unclog to manage our changelog)docs/orspec/) and code comments