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Fix race condition in subscription/listen - #1327
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Under highly contentious load, there might be a race condition in subscription/listen. Every change broadcast before subscribing to the change feed is lost. Subscription happens on a thread, and writing to the wire happens in another thread. The `ack` might be fully written to the transport, and received by the client, before the changes are subscribed to. A test harness might fire a change right after the test client receives `ack`, but before the changes are subscribed to, and therefore the change is lost. So we need to ensure that: 1. Changes are subscribed to BEFORE the ack 2. But the ACK goes first in any case (and only once) This is mostly a test-harness fix rather than a real-world scenario. Signed-off-by: Daniel Garnier-Moiroux <[email protected]>
Kehrlann
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subscription/listen
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Under highly contentious load, there might be a race condition in subscription/listen. Every change broadcast before subscribing to the change feed is lost. Subscription happens on a thread, and writing to the wire happens in another thread.
The
ackmight be fully written to the transport, and received by the client, before the changes are subscribed to.A test harness might fire a change right after the test client receives
ack, but before the changes are subscribed to, and therefore the change is lost.So we need to ensure that:
This is mostly a test-harness fix rather than a real-world scenario.