fix(data): Prevent semaphore deadlock within PersistentMutationOutbox #3115
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# Conflicts: # aws-datastore/src/main/java/com/amplifyframework/datastore/syncengine/PersistentMutationOutbox.kt
mattcreaser
reviewed
Aug 22, 2025
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Concept looks good. Instead of repeating the logic could we make an extension function like this?
fun Completable.acquireSemaphore(semaphore: Semaphore): Completable {
val semaphoreReleased = AtomicBoolean(false)
return this.doOnSubscribe { semaphore.acquire() }
.doOnTerminate {
if (semaphoreReleased.compareAndSet(false, true)) {
semaphore.release()
}
}
.doFinally {
if (semaphoreReleased.compareAndSet(false, true)) {
semaphore.release()
}
}
}
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Good suggestion. Done |
Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #3115 +/- ##
=======================================
Coverage 54.22% 54.23%
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Files 1038 1038
Lines 31989 32002 +13
Branches 4702 4704 +2
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+ Hits 17346 17356 +10
- Misses 12795 12799 +4
+ Partials 1848 1847 -1 🚀 New features to boost your workflow:
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mattcreaser
previously approved these changes
Aug 25, 2025
mattcreaser
approved these changes
Aug 25, 2025
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Issue #, if available:
Description of changes:
There's a scenario here that can happen with constant start/stops where neither
doOnTerminateanddoOnErrorget called to release the semaphore. If a completable is unsubscribed, doOnTerminate does not get called.doFinallywill always get called, however, it runs on a different thread. This should be safe, and seemed to work ok if we replaceddoOnTerminateentirely, but given the threading model, its best to release indoOnTerminate. ThedoFinallyis a new safety check that will only release if the semaphore was not already released indoOnTerminate.How did you test these changes?
(Please add a line here how the changes were tested)
Documentation update required?
General Checklist
fix(storage): message,feat(auth): message,chore(all): message)By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.