[WRR] fix bugs that caused us to re-enter blackout period upon updates #33694
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yousukseung
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Jul 13, 2023
markdroth
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grpc#33694) As per gRFC A58, when WRR sees a subchannel report READY, it reset the non_empty_since value, thus restarting the blackout period. However, there were two cases where we were incorrectly triggering this code: 1. When WRR got an updated address list that contained addresses that were already present on the old list and whose subchannels were already in READY state, the initial notification for those subchannels on the new list was READY, which incorrectly triggered resetting the non_empty_since value. 2. Due to a bug in the outlier_detection policy, whenever an update was propagated down through the OD policy without actually enabling OD, it would incorrectly send a duplicate connectivity state notification for the subchannels. This meant that a subchannel that was already in state READY would report READY again, which would also incorrectly trigger resetting the non_empty_since value. This PR makes two changes: 1. Fix the bug in outlier_detection that caused it to generate the spurious duplicate READY updates. 2. Fix WRR to reset the non_empty_since value when a subchannel goes READY only if the subchannel has seen a previous state update and only if that previous state was not READY. (The duplicate READY notifications should not actually happen anymore now that the OD policy has been fixed, but better to be defensive.) Fixes b/290983884.
apolcyn
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As per gRFC A58, when WRR sees a subchannel report READY, it reset the non_empty_since value, thus restarting the blackout period. However, there were two cases where we were incorrectly triggering this code:
This PR makes two changes:
Fixes b/290983884.