Test flake chase: MQTT: fix a very timing-sensitive behavior around Last Will and Testament message delivery#15995
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michaelklishin merged 2 commits intomainfrom Apr 10, 2026
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When Will-Delay-Interval >= Session-Expiry-Interval, the will queue's x-expires and the will message TTL were only ~5 ms apart. Under a loaded scheduler the queue could be deleted before the dead-letter path ran, silently dropping the will. Extend x-expires by a fixed 1 s margin. Strictly additive; the SessionExpiry = infinity case is unchanged.
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Apr 10, 2026
Test flake chase: MQTT: fix a very timing-sensitive behavior around Last Will and Testament message delivery (backport #15995)
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One change is just a bump of an unreasonably short timeout.
Another is a legitimate but very hard to reproduce bug in the MQTT plugin: avoid
a race condition between session expiry and the message expiry timer.
It takes quite a few runs to reproduce unless you pin the runtime to only use one scheduler.
The behavior change is reasonable given how specific the scenario is (two TTLs are at play, and the margin is fixed at 1s).