89 lines
2.5 KiB
Go
89 lines
2.5 KiB
Go
/*
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*
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* Copyright 2019 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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// Package resolver implements the xds resolver.
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//
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// At this point, the resolver is named xds-experimental, and doesn't do very
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// much at all, except for returning a hard-coded service config which selects
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// the xds_experimental balancer.
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package resolver
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import (
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"fmt"
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"google.golang.org/grpc/resolver"
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)
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const (
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// The JSON form of the hard-coded service config which picks the
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// xds_experimental balancer with round_robin as the child policy.
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jsonSC = `{
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"loadBalancingConfig":[
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{
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"xds_experimental":{
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"childPolicy":[
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{
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"round_robin": {}
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}
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]
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}
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}
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]
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}`
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// xDS balancer name is xds_experimental while resolver scheme is
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// xds-experimental since "_" is not a valid character in the URL.
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xdsScheme = "xds-experimental"
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)
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// NewBuilder creates a new implementation of the resolver.Builder interface
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// for the xDS resolver.
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func NewBuilder() resolver.Builder {
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return &xdsBuilder{}
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}
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type xdsBuilder struct{}
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// Build helps implement the resolver.Builder interface.
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func (b *xdsBuilder) Build(t resolver.Target, cc resolver.ClientConn, o resolver.BuildOptions) (resolver.Resolver, error) {
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// The xds balancer must have been registered at this point for the service
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// config to be parsed properly.
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scpr := cc.ParseServiceConfig(jsonSC)
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if scpr.Err != nil {
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panic(fmt.Sprintf("error parsing service config %q: %v", jsonSC, scpr.Err))
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}
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// We return a resolver which bacically does nothing. The hard-coded service
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// config returned here picks the xds balancer.
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cc.UpdateState(resolver.State{ServiceConfig: scpr})
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return &xdsResolver{}, nil
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}
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// Name helps implement the resolver.Builder interface.
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func (*xdsBuilder) Scheme() string {
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return xdsScheme
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}
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type xdsResolver struct{}
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// ResolveNow is a no-op at this point.
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func (*xdsResolver) ResolveNow(o resolver.ResolveNowOptions) {}
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// Close is a no-op at this point.
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func (*xdsResolver) Close() {}
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