xds: Plumb locality in xds_cluster_impl and weighted_target #11133
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As part of gRFC A78:
> To support the locality label in the WRR metrics, we will extend the
> `weighted_target` LB policy (see A28) to define a resolver attribute
> that indicates the name of its child. This attribute will be passed
> down to each of its children with the appropriate value, so that any
> LB policy that sits underneath the `weighted_target` policy will be
> able to use it.
xds_cluster_impl is involved because it uses the child names in the
AddressFilter, which must match the names used by weighted_target.
Instead of using Locality.toString() in multiple policies and assuming
the policies agree, we now have xds_cluster_impl decide the locality's
name and pass it down explicitly. This allows us to change the name
format to match gRFC A78:
> If locality information is available, the value of this label will be
> of the form `{region="${REGION}", zone="${ZONE}",
> sub_zone="${SUB_ZONE}"}`, where `${REGION}`, `${ZONE}`, and
> `${SUB_ZONE}` are replaced with the actual values. If no locality
> information is available, the label will be set to the empty string.
larry-safran
approved these changes
May 2, 2024
larry-safran
approved these changes
May 3, 2024
ejona86
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TODO:backport
ejona86
removed
the
TODO:backport
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As part of gRFC A78:
xds_cluster_impl is involved because it uses the child names in the AddressFilter, which must match the names used by weighted_target. Instead of using Locality.toString() in multiple policies and assuming the policies agree, we now have xds_cluster_impl decide the locality's name and pass it down explicitly. This allows us to change the name format to match gRFC A78:
CC @DNVindhya, @temawi. The API exposed to WRR will be
WeightedTargetLoadBalancer.CHILD_NAME