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1/*
2 *
3 * Copyright 2017 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19package grpc
20
21import (
22	"fmt"
23	"strings"
24
25	"google.golang.org/grpc/grpclog"
26	"google.golang.org/grpc/resolver"
27)
28
29// ccResolverWrapper is a wrapper on top of cc for resolvers.
30// It implements resolver.ClientConnection interface.
31type ccResolverWrapper struct {
32	cc       *ClientConn
33	resolver resolver.Resolver
34	addrCh   chan []resolver.Address
35	scCh     chan string
36	done     chan struct{}
37}
38
39// split2 returns the values from strings.SplitN(s, sep, 2).
40// If sep is not found, it returns ("", s, false) instead.
41func split2(s, sep string) (string, string, bool) {
42	spl := strings.SplitN(s, sep, 2)
43	if len(spl) < 2 {
44		return "", "", false
45	}
46	return spl[0], spl[1], true
47}
48
49// parseTarget splits target into a struct containing scheme, authority and
50// endpoint.
51//
52// If target is not a valid scheme://authority/endpoint, it returns {Endpoint:
53// target}.
54func parseTarget(target string) (ret resolver.Target) {
55	var ok bool
56	ret.Scheme, ret.Endpoint, ok = split2(target, "://")
57	if !ok {
58		return resolver.Target{Endpoint: target}
59	}
60	ret.Authority, ret.Endpoint, ok = split2(ret.Endpoint, "/")
61	if !ok {
62		return resolver.Target{Endpoint: target}
63	}
64	return ret
65}
66
67// newCCResolverWrapper parses cc.target for scheme and gets the resolver
68// builder for this scheme and builds the resolver. The monitoring goroutine
69// for it is not started yet and can be created by calling start().
70//
71// If withResolverBuilder dial option is set, the specified resolver will be
72// used instead.
73func newCCResolverWrapper(cc *ClientConn) (*ccResolverWrapper, error) {
74	rb := cc.dopts.resolverBuilder
75	if rb == nil {
76		return nil, fmt.Errorf("could not get resolver for scheme: %q", cc.parsedTarget.Scheme)
77	}
78
79	ccr := &ccResolverWrapper{
80		cc:     cc,
81		addrCh: make(chan []resolver.Address, 1),
82		scCh:   make(chan string, 1),
83		done:   make(chan struct{}),
84	}
85
86	var err error
87	ccr.resolver, err = rb.Build(cc.parsedTarget, ccr, resolver.BuildOption{DisableServiceConfig: cc.dopts.disableServiceConfig})
88	if err != nil {
89		return nil, err
90	}
91	return ccr, nil
92}
93
94func (ccr *ccResolverWrapper) start() {
95	go ccr.watcher()
96}
97
98// watcher processes address updates and service config updates sequentially.
99// Otherwise, we need to resolve possible races between address and service
100// config (e.g. they specify different balancer types).
101func (ccr *ccResolverWrapper) watcher() {
102	for {
103		select {
104		case <-ccr.done:
105			return
106		default:
107		}
108
109		select {
110		case addrs := <-ccr.addrCh:
111			select {
112			case <-ccr.done:
113				return
114			default:
115			}
116			grpclog.Infof("ccResolverWrapper: sending new addresses to cc: %v", addrs)
117			ccr.cc.handleResolvedAddrs(addrs, nil)
118		case sc := <-ccr.scCh:
119			select {
120			case <-ccr.done:
121				return
122			default:
123			}
124			grpclog.Infof("ccResolverWrapper: got new service config: %v", sc)
125			ccr.cc.handleServiceConfig(sc)
126		case <-ccr.done:
127			return
128		}
129	}
130}
131
132func (ccr *ccResolverWrapper) resolveNow(o resolver.ResolveNowOption) {
133	ccr.resolver.ResolveNow(o)
134}
135
136func (ccr *ccResolverWrapper) close() {
137	ccr.resolver.Close()
138	close(ccr.done)
139}
140
141// NewAddress is called by the resolver implemenetion to send addresses to gRPC.
142func (ccr *ccResolverWrapper) NewAddress(addrs []resolver.Address) {
143	select {
144	case <-ccr.addrCh:
145	default:
146	}
147	ccr.addrCh <- addrs
148}
149
150// NewServiceConfig is called by the resolver implemenetion to send service
151// configs to gRPC.
152func (ccr *ccResolverWrapper) NewServiceConfig(sc string) {
153	select {
154	case <-ccr.scCh:
155	default:
156	}
157	ccr.scCh <- sc
158}
159