mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-11-23 20:26:39 +00:00
248 lines
8.8 KiB
Go
248 lines
8.8 KiB
Go
/*
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*
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* Copyright 2017 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 grpc
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import (
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"context"
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"strings"
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"sync"
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"google.golang.org/grpc/balancer"
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"google.golang.org/grpc/internal/channelz"
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"google.golang.org/grpc/internal/grpcsync"
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"google.golang.org/grpc/internal/pretty"
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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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// resolverStateUpdater wraps the single method used by ccResolverWrapper to
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// report a state update from the actual resolver implementation.
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type resolverStateUpdater interface {
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updateResolverState(s resolver.State, err error) error
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}
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// ccResolverWrapper is a wrapper on top of cc for resolvers.
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// It implements resolver.ClientConn interface.
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type ccResolverWrapper struct {
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// The following fields are initialized when the wrapper is created and are
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// read-only afterwards, and therefore can be accessed without a mutex.
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cc resolverStateUpdater
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channelzID *channelz.Identifier
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ignoreServiceConfig bool
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opts ccResolverWrapperOpts
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serializer *grpcsync.CallbackSerializer // To serialize all incoming calls.
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serializerCancel context.CancelFunc // To close the serializer, accessed only from close().
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// All incoming (resolver --> gRPC) calls are guaranteed to execute in a
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// mutually exclusive manner as they are scheduled on the serializer.
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// Fields accessed *only* in these serializer callbacks, can therefore be
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// accessed without a mutex.
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curState resolver.State
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// mu guards access to the below fields.
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mu sync.Mutex
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closed bool
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resolver resolver.Resolver // Accessed only from outgoing calls.
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}
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// ccResolverWrapperOpts wraps the arguments to be passed when creating a new
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// ccResolverWrapper.
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type ccResolverWrapperOpts struct {
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target resolver.Target // User specified dial target to resolve.
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builder resolver.Builder // Resolver builder to use.
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bOpts resolver.BuildOptions // Resolver build options to use.
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channelzID *channelz.Identifier // Channelz identifier for the channel.
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}
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// newCCResolverWrapper uses the resolver.Builder to build a Resolver and
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// returns a ccResolverWrapper object which wraps the newly built resolver.
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func newCCResolverWrapper(cc resolverStateUpdater, opts ccResolverWrapperOpts) (*ccResolverWrapper, error) {
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ctx, cancel := context.WithCancel(context.Background())
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ccr := &ccResolverWrapper{
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cc: cc,
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channelzID: opts.channelzID,
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ignoreServiceConfig: opts.bOpts.DisableServiceConfig,
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opts: opts,
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serializer: grpcsync.NewCallbackSerializer(ctx),
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serializerCancel: cancel,
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}
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// Cannot hold the lock at build time because the resolver can send an
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// update or error inline and these incoming calls grab the lock to schedule
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// a callback in the serializer.
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r, err := opts.builder.Build(opts.target, ccr, opts.bOpts)
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if err != nil {
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cancel()
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return nil, err
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}
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// Any error reported by the resolver at build time that leads to a
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// re-resolution request from the balancer is dropped by grpc until we
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// return from this function. So, we don't have to handle pending resolveNow
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// requests here.
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ccr.mu.Lock()
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ccr.resolver = r
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ccr.mu.Unlock()
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return ccr, nil
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}
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func (ccr *ccResolverWrapper) resolveNow(o resolver.ResolveNowOptions) {
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ccr.mu.Lock()
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defer ccr.mu.Unlock()
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// ccr.resolver field is set only after the call to Build() returns. But in
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// the process of building, the resolver may send an error update which when
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// propagated to the balancer may result in a re-resolution request.
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if ccr.closed || ccr.resolver == nil {
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return
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}
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ccr.resolver.ResolveNow(o)
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}
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func (ccr *ccResolverWrapper) close() {
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ccr.mu.Lock()
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if ccr.closed {
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ccr.mu.Unlock()
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return
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}
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channelz.Info(logger, ccr.channelzID, "Closing the name resolver")
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// Close the serializer to ensure that no more calls from the resolver are
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// handled, before actually closing the resolver.
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ccr.serializerCancel()
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ccr.closed = true
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r := ccr.resolver
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ccr.mu.Unlock()
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// Give enqueued callbacks a chance to finish.
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<-ccr.serializer.Done()
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// Spawn a goroutine to close the resolver (since it may block trying to
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// cleanup all allocated resources) and return early.
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go r.Close()
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}
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// serializerScheduleLocked is a convenience method to schedule a function to be
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// run on the serializer while holding ccr.mu.
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func (ccr *ccResolverWrapper) serializerScheduleLocked(f func(context.Context)) {
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ccr.mu.Lock()
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ccr.serializer.Schedule(f)
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ccr.mu.Unlock()
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}
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// UpdateState is called by resolver implementations to report new state to gRPC
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// which includes addresses and service config.
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func (ccr *ccResolverWrapper) UpdateState(s resolver.State) error {
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errCh := make(chan error, 1)
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if s.Endpoints == nil {
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s.Endpoints = make([]resolver.Endpoint, 0, len(s.Addresses))
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for _, a := range s.Addresses {
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ep := resolver.Endpoint{Addresses: []resolver.Address{a}, Attributes: a.BalancerAttributes}
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ep.Addresses[0].BalancerAttributes = nil
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s.Endpoints = append(s.Endpoints, ep)
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}
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}
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ok := ccr.serializer.Schedule(func(context.Context) {
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ccr.addChannelzTraceEvent(s)
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ccr.curState = s
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if err := ccr.cc.updateResolverState(ccr.curState, nil); err == balancer.ErrBadResolverState {
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errCh <- balancer.ErrBadResolverState
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return
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}
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errCh <- nil
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})
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if !ok {
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// The only time when Schedule() fail to add the callback to the
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// serializer is when the serializer is closed, and this happens only
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// when the resolver wrapper is closed.
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return nil
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}
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return <-errCh
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}
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// ReportError is called by resolver implementations to report errors
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// encountered during name resolution to gRPC.
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func (ccr *ccResolverWrapper) ReportError(err error) {
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ccr.serializerScheduleLocked(func(_ context.Context) {
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channelz.Warningf(logger, ccr.channelzID, "ccResolverWrapper: reporting error to cc: %v", err)
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ccr.cc.updateResolverState(resolver.State{}, err)
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})
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}
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// NewAddress is called by the resolver implementation to send addresses to
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// gRPC.
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func (ccr *ccResolverWrapper) NewAddress(addrs []resolver.Address) {
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ccr.serializerScheduleLocked(func(_ context.Context) {
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ccr.addChannelzTraceEvent(resolver.State{Addresses: addrs, ServiceConfig: ccr.curState.ServiceConfig})
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ccr.curState.Addresses = addrs
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ccr.cc.updateResolverState(ccr.curState, nil)
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})
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}
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// NewServiceConfig is called by the resolver implementation to send service
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// configs to gRPC.
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func (ccr *ccResolverWrapper) NewServiceConfig(sc string) {
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ccr.serializerScheduleLocked(func(_ context.Context) {
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channelz.Infof(logger, ccr.channelzID, "ccResolverWrapper: got new service config: %s", sc)
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if ccr.ignoreServiceConfig {
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channelz.Info(logger, ccr.channelzID, "Service config lookups disabled; ignoring config")
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return
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}
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scpr := parseServiceConfig(sc)
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if scpr.Err != nil {
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channelz.Warningf(logger, ccr.channelzID, "ccResolverWrapper: error parsing service config: %v", scpr.Err)
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return
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}
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ccr.addChannelzTraceEvent(resolver.State{Addresses: ccr.curState.Addresses, ServiceConfig: scpr})
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ccr.curState.ServiceConfig = scpr
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ccr.cc.updateResolverState(ccr.curState, nil)
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})
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}
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// ParseServiceConfig is called by resolver implementations to parse a JSON
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// representation of the service config.
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func (ccr *ccResolverWrapper) ParseServiceConfig(scJSON string) *serviceconfig.ParseResult {
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return parseServiceConfig(scJSON)
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}
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// addChannelzTraceEvent adds a channelz trace event containing the new
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// state received from resolver implementations.
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func (ccr *ccResolverWrapper) addChannelzTraceEvent(s resolver.State) {
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var updates []string
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var oldSC, newSC *ServiceConfig
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var oldOK, newOK bool
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if ccr.curState.ServiceConfig != nil {
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oldSC, oldOK = ccr.curState.ServiceConfig.Config.(*ServiceConfig)
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}
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if s.ServiceConfig != nil {
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newSC, newOK = s.ServiceConfig.Config.(*ServiceConfig)
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}
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if oldOK != newOK || (oldOK && newOK && oldSC.rawJSONString != newSC.rawJSONString) {
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updates = append(updates, "service config updated")
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}
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if len(ccr.curState.Addresses) > 0 && len(s.Addresses) == 0 {
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updates = append(updates, "resolver returned an empty address list")
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} else if len(ccr.curState.Addresses) == 0 && len(s.Addresses) > 0 {
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updates = append(updates, "resolver returned new addresses")
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}
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channelz.Infof(logger, ccr.channelzID, "Resolver state updated: %s (%v)", pretty.ToJSON(s), strings.Join(updates, "; "))
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}
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