core: round robin should ignore name resolution error for channel state change when there are READY subchannels #7595
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…READY subchannels.
ejona86
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Nov 4, 2020
dfawley
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Jan 15, 2021
…te change when there are READY subchannels (grpc#7595) Round robin is keeping use of READY subchannels even if there is name resolution error. However, it moves Channel state to TRANSIENT_ERROR. In hierarchical load balancers, the upstream LB policy may need to aggregate pickers from multiple downstream round_robin LB policy while filtering out non-ready subchannels. It cannot infer if the subchannel can be used just from the SubchannelPicker interface. It relies on the state that the round_robin intends to set channel to. So the change is to match the readiness of the picker/subchannel with the state that round_robin tries to update. It will completely ignore name resolution error if there are READY subchannels.
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Round robin is keeping use of READY subchannels even if there is name resolution error. However, it moves Channel state to TRANSIENT_ERROR.
In hierarchical load balancers, the upstream LB policy may need to aggregate pickers from multiple downstream round_robin LB policy while filtering out non-ready subchannels. It cannot infer if the subchannel can be used just from the
SubchannelPickerinterface. It relies on the state that the round_robin intends to set channel to.So the change is to match the readiness of the picker/subchannel with the state that round_robin tries to update. It will completely ignore name resolution error if there are READY subchannels.
/cc @zhangkun83