127 lines
4.0 KiB
Go
127 lines
4.0 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 manual defines a resolver that can be used to manually send resolved
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// addresses to ClientConn.
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package manual
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import (
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"sync"
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"google.golang.org/grpc/resolver"
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)
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// NewBuilderWithScheme creates a new manual resolver builder with the given
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// scheme. Every instance of the manual resolver may only ever be used with a
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// single grpc.ClientConn. Otherwise, bad things will happen.
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func NewBuilderWithScheme(scheme string) *Resolver {
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return &Resolver{
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BuildCallback: func(resolver.Target, resolver.ClientConn, resolver.BuildOptions) {},
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UpdateStateCallback: func(error) {},
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ResolveNowCallback: func(resolver.ResolveNowOptions) {},
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CloseCallback: func() {},
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scheme: scheme,
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}
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}
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// Resolver is also a resolver builder.
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// It's build() function always returns itself.
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type Resolver struct {
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// BuildCallback is called when the Build method is called. Must not be
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// nil. Must not be changed after the resolver may be built.
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BuildCallback func(resolver.Target, resolver.ClientConn, resolver.BuildOptions)
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// UpdateStateCallback is called when the UpdateState method is called on
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// the resolver. The value passed as argument to this callback is the value
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// returned by the resolver.ClientConn. Must not be nil. Must not be
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// changed after the resolver may be built.
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UpdateStateCallback func(err error)
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// ResolveNowCallback is called when the ResolveNow method is called on the
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// resolver. Must not be nil. Must not be changed after the resolver may
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// be built.
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ResolveNowCallback func(resolver.ResolveNowOptions)
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// CloseCallback is called when the Close method is called. Must not be
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// nil. Must not be changed after the resolver may be built.
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CloseCallback func()
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scheme string
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// Fields actually belong to the resolver.
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// Guards access to below fields.
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mu sync.Mutex
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CC resolver.ClientConn
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// Storing the most recent state update makes this resolver resilient to
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// restarts, which is possible with channel idleness.
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lastSeenState *resolver.State
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}
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// InitialState adds initial state to the resolver so that UpdateState doesn't
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// need to be explicitly called after Dial.
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func (r *Resolver) InitialState(s resolver.State) {
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r.lastSeenState = &s
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}
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// Build returns itself for Resolver, because it's both a builder and a resolver.
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func (r *Resolver) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
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r.BuildCallback(target, cc, opts)
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r.mu.Lock()
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defer r.mu.Unlock()
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r.CC = cc
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if r.lastSeenState != nil {
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err := r.CC.UpdateState(*r.lastSeenState)
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go r.UpdateStateCallback(err)
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}
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return r, nil
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}
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// Scheme returns the manual resolver's scheme.
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func (r *Resolver) Scheme() string {
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return r.scheme
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}
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// ResolveNow is a noop for Resolver.
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func (r *Resolver) ResolveNow(o resolver.ResolveNowOptions) {
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r.ResolveNowCallback(o)
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}
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// Close is a noop for Resolver.
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func (r *Resolver) Close() {
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r.CloseCallback()
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}
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// UpdateState calls CC.UpdateState.
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func (r *Resolver) UpdateState(s resolver.State) {
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r.mu.Lock()
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defer r.mu.Unlock()
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var err error
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if r.CC == nil {
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panic("cannot update state as grpc.Dial with resolver has not been called")
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}
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err = r.CC.UpdateState(s)
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r.lastSeenState = &s
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r.UpdateStateCallback(err)
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}
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// ReportError calls CC.ReportError.
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func (r *Resolver) ReportError(err error) {
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r.mu.Lock()
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defer r.mu.Unlock()
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if r.CC == nil {
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panic("cannot report error as grpc.Dial with resolver has not been called")
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}
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r.CC.ReportError(err)
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}
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