[LB policies] fix handling of UpdateLocked() result #36463
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markdroth
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…lazy_child_creation
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eugeneo
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May 1, 2024
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It isn't really observable from the outside, because these cases can't happen today. I am adding the plumbing just as a defense against potential future changes that could introduce such cases. |
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This fixes some TODOs added in #30809 for cases where LB policies lazily create child policies. Credit to @ejona86 for pointing out that simply calling
RequestReresolution()in this case will ultimately result in the exponential backoff behavior we want.This also adds some missing plumbing in code added as part of the dualstack work (in the endpoint_list library and in ring_hash) to propagate non-OK statuses from
UpdateLocked(). When I first made the dualstack changes, I didn't bother with this plumbing, because there are no cases today where these code-paths will actually see a non-OK status (EndpointAddresseswon't allow creating an endpoint with 0 addresses, and that's the only case where pick_first will return a non-OK status), and I wasn't sure if we would stick with the approach of returning status fromUpdateLocked()due to the aforementioned lazy creation case. However, now that we have a good solution for the lazy creation case, I've added the necessary plumbing, just so that we don't have a bug if in the future pick_first winds up returning non-OK status in some other case.I have not bothered to fix the propagation in the grpclb policy, since that looked like it would be slightly more work than it's really worth at this point.