mirror of https://github.com/grpc/grpc-go.git
115 lines
3.2 KiB
Go
115 lines
3.2 KiB
Go
/*
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*
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* Copyright 2021 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 clusterresolver
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import (
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"fmt"
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"google.golang.org/grpc/resolver"
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"google.golang.org/grpc/serviceconfig"
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)
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var (
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newDNS = func(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
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// The dns resolver is registered by the grpc package. So, this call to
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// resolver.Get() is never expected to return nil.
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return resolver.Get("dns").Build(target, cc, opts)
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}
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)
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// dnsDiscoveryMechanism watches updates for the given DNS hostname.
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//
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// It implements resolver.ClientConn interface to work with the DNS resolver.
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type dnsDiscoveryMechanism struct {
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target string
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topLevelResolver *resourceResolver
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r resolver.Resolver
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addrs []string
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updateReceived bool
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}
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func newDNSResolver(target string, topLevelResolver *resourceResolver) *dnsDiscoveryMechanism {
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ret := &dnsDiscoveryMechanism{
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target: target,
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topLevelResolver: topLevelResolver,
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}
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r, err := newDNS(resolver.Target{Scheme: "dns", Endpoint: target}, ret, resolver.BuildOptions{})
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if err != nil {
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select {
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case <-topLevelResolver.updateChannel:
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default:
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}
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topLevelResolver.updateChannel <- &resourceUpdate{err: err}
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}
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ret.r = r
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return ret
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}
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func (dr *dnsDiscoveryMechanism) lastUpdate() (interface{}, bool) {
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if !dr.updateReceived {
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return nil, false
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}
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return dr.addrs, true
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}
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func (dr *dnsDiscoveryMechanism) resolveNow() {
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dr.r.ResolveNow(resolver.ResolveNowOptions{})
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}
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func (dr *dnsDiscoveryMechanism) stop() {
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dr.r.Close()
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}
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// dnsDiscoveryMechanism needs to implement resolver.ClientConn interface to receive
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// updates from the real DNS resolver.
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func (dr *dnsDiscoveryMechanism) UpdateState(state resolver.State) error {
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dr.topLevelResolver.mu.Lock()
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defer dr.topLevelResolver.mu.Unlock()
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addrs := make([]string, len(state.Addresses))
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for i, a := range state.Addresses {
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addrs[i] = a.Addr
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}
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dr.addrs = addrs
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dr.updateReceived = true
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dr.topLevelResolver.generate()
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return nil
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}
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func (dr *dnsDiscoveryMechanism) ReportError(err error) {
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select {
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case <-dr.topLevelResolver.updateChannel:
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default:
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}
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dr.topLevelResolver.updateChannel <- &resourceUpdate{err: err}
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}
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func (dr *dnsDiscoveryMechanism) NewAddress(addresses []resolver.Address) {
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dr.UpdateState(resolver.State{Addresses: addresses})
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}
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func (dr *dnsDiscoveryMechanism) NewServiceConfig(string) {
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// This method is deprecated, and service config isn't supported.
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}
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func (dr *dnsDiscoveryMechanism) ParseServiceConfig(string) *serviceconfig.ParseResult {
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return &serviceconfig.ParseResult{Err: fmt.Errorf("service config not supported")}
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}
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