reproduce signal delivery ordering misunderstaning #251
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jkachmar
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📊 Code Coverage ReportCurrent PR CoverageOverall Coverage: 🟠 57.9%
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🟢 ≥80% 🟡 ≥60% 🟠 ≥40% 🔴 <40% 📈 Coverage Comparison vs. Main✅ Coverage increased by .1% (57.8% → 57.9%) Main Branch Coverage (for comparison)Overall Coverage: 🟠 57.8%
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jkachmar
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Nov 21, 2025
sdk/test/IntegrationSpec.hs
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| signalWithArgs | ||
| 1 | ||
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| -- liftIO $ threadDelay 1_000 |
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the test succeeds if this line is uncommented, so it looks like there is some sort of window of time affecting how state var changes get sequenced
jkachmar
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Nov 21, 2025
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| t <- now | ||
| readStateVar var >>= \s -> writeStateVar var (MinPQueue.insert t i s) |
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the fact that this works implies that things are getting processed in-order, so it looks like statevar operations are messed up.
fwiw i also tried this with modifyStateVar & it reproduced the issue which means it's not a read *> write sequence issue.
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description
this reproduces signal delivery ordering behavior we observed in production code, where
signalWithStartfollowed bysignalin short succession does not necessarily guarantee in-order modification ofStateVars.signals are, however, processed in-order: if the signal handler gets the time at which it is processed with
Workflow.nowand uses that as a priority ordering key then things look the way that we expect them to.6c0e06b fails with the same thing we saw in prod:
failure
...but 2946fc5 succeeds when it uses a priority queue to insert according to received timestamp:
success