mvcc: avoid negative watcher count metrics #11879
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jackkleeman
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The watch count metrics are not robust to duplicate cancellations. These cause the count to be decremented twice, leading eventually to negative counts. We are seeing this in production. The duplicate cancellations themselves are not themselves a big problem (except performance), but they are caused by the new proactive cancellation logic (etcd-io#11850). As it turns out, w.closingc seems to receive two messages for a cancellation. I have added a fix which ensures that we won't send duplicate cancel requests.
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see #11882 for revised fix, the client changes here weren't quite right |
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The watch count metrics are not robust to duplicate cancellations. These
cause the count to be decremented twice, leading eventually to negative
counts. We are seeing this in production. The duplicate cancellations
themselves are not themselves a big problem (except performance), but
they are caused by the new proactive cancellation logic (#11850). As it
turns out, w.closingc seems to receive two messages for a cancellation.
I have added a fix which ensures that we won't send duplicate cancel
requests.