grpclb: only force update picker when cache is used #2843
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dfawley
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May 30, 2019
menghanl
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Only when sub-balancer is round-robin (not pick-first), subconns are cached.
The actual problem solved by this:
If pick-first is set as the sub-balancer, when switching sub-balancer from round-robin to pick-first, the first subconn creation will fail because no address is available (
grpclb: failed to create new SubConn: grpc: cannot create SubConn with empty address list).What should happen is, no picker is updated, and all RPCs block and wait. But because we will always regenerate and update picker, a TransientFailure error picker will be set and all RPCs will fail.