Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 1 | /* |
| 2 | * |
| 3 | * Copyright 2018 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 | |
| 19 | // Package dns implements a dns resolver to be installed as the default resolver |
| 20 | // in grpc. |
| 21 | package dns |
| 22 | |
| 23 | import ( |
| 24 | "context" |
| 25 | "encoding/json" |
| 26 | "errors" |
| 27 | "fmt" |
| 28 | "net" |
| 29 | "os" |
| 30 | "strconv" |
| 31 | "strings" |
| 32 | "sync" |
| 33 | "time" |
| 34 | |
| 35 | "google.golang.org/grpc/grpclog" |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 36 | "google.golang.org/grpc/internal/envconfig" |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 37 | "google.golang.org/grpc/internal/grpcrand" |
| 38 | "google.golang.org/grpc/resolver" |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 39 | "google.golang.org/grpc/serviceconfig" |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 40 | ) |
| 41 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 42 | // EnableSRVLookups controls whether the DNS resolver attempts to fetch gRPCLB |
| 43 | // addresses from SRV records. Must not be changed after init time. |
| 44 | var EnableSRVLookups = false |
| 45 | |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 46 | func init() { |
| 47 | resolver.Register(NewBuilder()) |
| 48 | } |
| 49 | |
| 50 | const ( |
| 51 | defaultPort = "443" |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 52 | defaultDNSSvrPort = "53" |
| 53 | golang = "GO" |
| 54 | // txtPrefix is the prefix string to be prepended to the host name for txt record lookup. |
| 55 | txtPrefix = "_grpc_config." |
| 56 | // In DNS, service config is encoded in a TXT record via the mechanism |
| 57 | // described in RFC-1464 using the attribute name grpc_config. |
| 58 | txtAttribute = "grpc_config=" |
| 59 | ) |
| 60 | |
| 61 | var ( |
| 62 | errMissingAddr = errors.New("dns resolver: missing address") |
| 63 | |
| 64 | // Addresses ending with a colon that is supposed to be the separator |
| 65 | // between host and port is not allowed. E.g. "::" is a valid address as |
| 66 | // it is an IPv6 address (host only) and "[::]:" is invalid as it ends with |
| 67 | // a colon as the host and port separator |
| 68 | errEndsWithColon = errors.New("dns resolver: missing port after port-separator colon") |
| 69 | ) |
| 70 | |
| 71 | var ( |
| 72 | defaultResolver netResolver = net.DefaultResolver |
| 73 | // To prevent excessive re-resolution, we enforce a rate limit on DNS |
| 74 | // resolution requests. |
| 75 | minDNSResRate = 30 * time.Second |
| 76 | ) |
| 77 | |
| 78 | var customAuthorityDialler = func(authority string) func(ctx context.Context, network, address string) (net.Conn, error) { |
| 79 | return func(ctx context.Context, network, address string) (net.Conn, error) { |
| 80 | var dialer net.Dialer |
| 81 | return dialer.DialContext(ctx, network, authority) |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | var customAuthorityResolver = func(authority string) (netResolver, error) { |
| 86 | host, port, err := parseTarget(authority, defaultDNSSvrPort) |
| 87 | if err != nil { |
| 88 | return nil, err |
| 89 | } |
| 90 | |
| 91 | authorityWithPort := net.JoinHostPort(host, port) |
| 92 | |
| 93 | return &net.Resolver{ |
| 94 | PreferGo: true, |
| 95 | Dial: customAuthorityDialler(authorityWithPort), |
| 96 | }, nil |
| 97 | } |
| 98 | |
| 99 | // NewBuilder creates a dnsBuilder which is used to factory DNS resolvers. |
| 100 | func NewBuilder() resolver.Builder { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 101 | return &dnsBuilder{} |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 102 | } |
| 103 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 104 | type dnsBuilder struct{} |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 105 | |
| 106 | // Build creates and starts a DNS resolver that watches the name resolution of the target. |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 107 | func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) { |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 108 | host, port, err := parseTarget(target.Endpoint, defaultPort) |
| 109 | if err != nil { |
| 110 | return nil, err |
| 111 | } |
| 112 | |
| 113 | // IP address. |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 114 | if ipAddr, ok := formatIP(host); ok { |
| 115 | addr := []resolver.Address{{Addr: ipAddr + ":" + port}} |
| 116 | cc.UpdateState(resolver.State{Addresses: addr}) |
| 117 | return deadResolver{}, nil |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 118 | } |
| 119 | |
| 120 | // DNS address (non-IP). |
| 121 | ctx, cancel := context.WithCancel(context.Background()) |
| 122 | d := &dnsResolver{ |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 123 | host: host, |
| 124 | port: port, |
| 125 | ctx: ctx, |
| 126 | cancel: cancel, |
| 127 | cc: cc, |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 128 | rn: make(chan struct{}, 1), |
| 129 | disableServiceConfig: opts.DisableServiceConfig, |
| 130 | } |
| 131 | |
| 132 | if target.Authority == "" { |
| 133 | d.resolver = defaultResolver |
| 134 | } else { |
| 135 | d.resolver, err = customAuthorityResolver(target.Authority) |
| 136 | if err != nil { |
| 137 | return nil, err |
| 138 | } |
| 139 | } |
| 140 | |
| 141 | d.wg.Add(1) |
| 142 | go d.watcher() |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 143 | d.ResolveNow(resolver.ResolveNowOptions{}) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 144 | return d, nil |
| 145 | } |
| 146 | |
| 147 | // Scheme returns the naming scheme of this resolver builder, which is "dns". |
| 148 | func (b *dnsBuilder) Scheme() string { |
| 149 | return "dns" |
| 150 | } |
| 151 | |
| 152 | type netResolver interface { |
| 153 | LookupHost(ctx context.Context, host string) (addrs []string, err error) |
| 154 | LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error) |
| 155 | LookupTXT(ctx context.Context, name string) (txts []string, err error) |
| 156 | } |
| 157 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 158 | // deadResolver is a resolver that does nothing. |
| 159 | type deadResolver struct{} |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 160 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 161 | func (deadResolver) ResolveNow(resolver.ResolveNowOptions) {} |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 162 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 163 | func (deadResolver) Close() {} |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 164 | |
| 165 | // dnsResolver watches for the name resolution update for a non-IP target. |
| 166 | type dnsResolver struct { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 167 | host string |
| 168 | port string |
| 169 | resolver netResolver |
| 170 | ctx context.Context |
| 171 | cancel context.CancelFunc |
| 172 | cc resolver.ClientConn |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 173 | // rn channel is used by ResolveNow() to force an immediate resolution of the target. |
| 174 | rn chan struct{} |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 175 | // wg is used to enforce Close() to return after the watcher() goroutine has finished. |
| 176 | // Otherwise, data race will be possible. [Race Example] in dns_resolver_test we |
| 177 | // replace the real lookup functions with mocked ones to facilitate testing. |
| 178 | // If Close() doesn't wait for watcher() goroutine finishes, race detector sometimes |
| 179 | // will warns lookup (READ the lookup function pointers) inside watcher() goroutine |
| 180 | // has data race with replaceNetFunc (WRITE the lookup function pointers). |
| 181 | wg sync.WaitGroup |
| 182 | disableServiceConfig bool |
| 183 | } |
| 184 | |
| 185 | // ResolveNow invoke an immediate resolution of the target that this dnsResolver watches. |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 186 | func (d *dnsResolver) ResolveNow(resolver.ResolveNowOptions) { |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 187 | select { |
| 188 | case d.rn <- struct{}{}: |
| 189 | default: |
| 190 | } |
| 191 | } |
| 192 | |
| 193 | // Close closes the dnsResolver. |
| 194 | func (d *dnsResolver) Close() { |
| 195 | d.cancel() |
| 196 | d.wg.Wait() |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 197 | } |
| 198 | |
| 199 | func (d *dnsResolver) watcher() { |
| 200 | defer d.wg.Done() |
| 201 | for { |
| 202 | select { |
| 203 | case <-d.ctx.Done(): |
| 204 | return |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 205 | case <-d.rn: |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 206 | } |
| 207 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 208 | state, err := d.lookup() |
| 209 | if err != nil { |
| 210 | d.cc.ReportError(err) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 211 | } else { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 212 | d.cc.UpdateState(*state) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 213 | } |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 214 | |
| 215 | // Sleep to prevent excessive re-resolutions. Incoming resolution requests |
| 216 | // will be queued in d.rn. |
| 217 | t := time.NewTimer(minDNSResRate) |
| 218 | select { |
| 219 | case <-t.C: |
| 220 | case <-d.ctx.Done(): |
| 221 | t.Stop() |
| 222 | return |
| 223 | } |
| 224 | } |
| 225 | } |
| 226 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 227 | func (d *dnsResolver) lookupSRV() ([]resolver.Address, error) { |
| 228 | if !EnableSRVLookups { |
| 229 | return nil, nil |
| 230 | } |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 231 | var newAddrs []resolver.Address |
| 232 | _, srvs, err := d.resolver.LookupSRV(d.ctx, "grpclb", "tcp", d.host) |
| 233 | if err != nil { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 234 | err = handleDNSError(err, "SRV") // may become nil |
| 235 | return nil, err |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 236 | } |
| 237 | for _, s := range srvs { |
| 238 | lbAddrs, err := d.resolver.LookupHost(d.ctx, s.Target) |
| 239 | if err != nil { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 240 | err = handleDNSError(err, "A") // may become nil |
| 241 | if err == nil { |
| 242 | // If there are other SRV records, look them up and ignore this |
| 243 | // one that does not exist. |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 244 | continue |
| 245 | } |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 246 | return nil, err |
| 247 | } |
| 248 | for _, a := range lbAddrs { |
| 249 | ip, ok := formatIP(a) |
| 250 | if !ok { |
| 251 | return nil, fmt.Errorf("dns: error parsing A record IP address %v", a) |
| 252 | } |
| 253 | addr := ip + ":" + strconv.Itoa(int(s.Port)) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 254 | newAddrs = append(newAddrs, resolver.Address{Addr: addr, Type: resolver.GRPCLB, ServerName: s.Target}) |
| 255 | } |
| 256 | } |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 257 | return newAddrs, nil |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 258 | } |
| 259 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 260 | var filterError = func(err error) error { |
| 261 | if dnsErr, ok := err.(*net.DNSError); ok && !dnsErr.IsTimeout && !dnsErr.IsTemporary { |
| 262 | // Timeouts and temporary errors should be communicated to gRPC to |
| 263 | // attempt another DNS query (with backoff). Other errors should be |
| 264 | // suppressed (they may represent the absence of a TXT record). |
| 265 | return nil |
| 266 | } |
| 267 | return err |
| 268 | } |
| 269 | |
| 270 | func handleDNSError(err error, lookupType string) error { |
| 271 | err = filterError(err) |
| 272 | if err != nil { |
| 273 | err = fmt.Errorf("dns: %v record lookup error: %v", lookupType, err) |
| 274 | grpclog.Infoln(err) |
| 275 | } |
| 276 | return err |
| 277 | } |
| 278 | |
| 279 | func (d *dnsResolver) lookupTXT() *serviceconfig.ParseResult { |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 280 | ss, err := d.resolver.LookupTXT(d.ctx, txtPrefix+d.host) |
| 281 | if err != nil { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 282 | if envconfig.TXTErrIgnore { |
| 283 | return nil |
| 284 | } |
| 285 | if err = handleDNSError(err, "TXT"); err != nil { |
| 286 | return &serviceconfig.ParseResult{Err: err} |
| 287 | } |
| 288 | return nil |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 289 | } |
| 290 | var res string |
| 291 | for _, s := range ss { |
| 292 | res += s |
| 293 | } |
| 294 | |
| 295 | // TXT record must have "grpc_config=" attribute in order to be used as service config. |
| 296 | if !strings.HasPrefix(res, txtAttribute) { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 297 | grpclog.Warningf("dns: TXT record %v missing %v attribute", res, txtAttribute) |
| 298 | // This is not an error; it is the equivalent of not having a service config. |
| 299 | return nil |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 300 | } |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 301 | sc := canaryingSC(strings.TrimPrefix(res, txtAttribute)) |
| 302 | return d.cc.ParseServiceConfig(sc) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 303 | } |
| 304 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 305 | func (d *dnsResolver) lookupHost() ([]resolver.Address, error) { |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 306 | var newAddrs []resolver.Address |
| 307 | addrs, err := d.resolver.LookupHost(d.ctx, d.host) |
| 308 | if err != nil { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 309 | err = handleDNSError(err, "A") |
| 310 | return nil, err |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 311 | } |
| 312 | for _, a := range addrs { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 313 | ip, ok := formatIP(a) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 314 | if !ok { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 315 | return nil, fmt.Errorf("dns: error parsing A record IP address %v", a) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 316 | } |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 317 | addr := ip + ":" + d.port |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 318 | newAddrs = append(newAddrs, resolver.Address{Addr: addr}) |
| 319 | } |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 320 | return newAddrs, nil |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 321 | } |
| 322 | |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 323 | func (d *dnsResolver) lookup() (*resolver.State, error) { |
| 324 | srv, srvErr := d.lookupSRV() |
| 325 | addrs, hostErr := d.lookupHost() |
| 326 | if hostErr != nil && (srvErr != nil || len(srv) == 0) { |
| 327 | return nil, hostErr |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 328 | } |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 329 | state := &resolver.State{ |
| 330 | Addresses: append(addrs, srv...), |
| 331 | } |
| 332 | if !d.disableServiceConfig { |
| 333 | state.ServiceConfig = d.lookupTXT() |
| 334 | } |
| 335 | return state, nil |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 336 | } |
| 337 | |
| 338 | // formatIP returns ok = false if addr is not a valid textual representation of an IP address. |
| 339 | // If addr is an IPv4 address, return the addr and ok = true. |
| 340 | // If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true. |
| 341 | func formatIP(addr string) (addrIP string, ok bool) { |
| 342 | ip := net.ParseIP(addr) |
| 343 | if ip == nil { |
| 344 | return "", false |
| 345 | } |
| 346 | if ip.To4() != nil { |
| 347 | return addr, true |
| 348 | } |
| 349 | return "[" + addr + "]", true |
| 350 | } |
| 351 | |
| 352 | // parseTarget takes the user input target string and default port, returns formatted host and port info. |
| 353 | // If target doesn't specify a port, set the port to be the defaultPort. |
| 354 | // If target is in IPv6 format and host-name is enclosed in square brackets, brackets |
| 355 | // are stripped when setting the host. |
| 356 | // examples: |
| 357 | // target: "www.google.com" defaultPort: "443" returns host: "www.google.com", port: "443" |
| 358 | // target: "ipv4-host:80" defaultPort: "443" returns host: "ipv4-host", port: "80" |
| 359 | // target: "[ipv6-host]" defaultPort: "443" returns host: "ipv6-host", port: "443" |
| 360 | // target: ":80" defaultPort: "443" returns host: "localhost", port: "80" |
| 361 | func parseTarget(target, defaultPort string) (host, port string, err error) { |
| 362 | if target == "" { |
| 363 | return "", "", errMissingAddr |
| 364 | } |
| 365 | if ip := net.ParseIP(target); ip != nil { |
| 366 | // target is an IPv4 or IPv6(without brackets) address |
| 367 | return target, defaultPort, nil |
| 368 | } |
| 369 | if host, port, err = net.SplitHostPort(target); err == nil { |
| 370 | if port == "" { |
| 371 | // If the port field is empty (target ends with colon), e.g. "[::1]:", this is an error. |
| 372 | return "", "", errEndsWithColon |
| 373 | } |
| 374 | // target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port |
| 375 | if host == "" { |
| 376 | // Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed. |
| 377 | host = "localhost" |
| 378 | } |
| 379 | return host, port, nil |
| 380 | } |
| 381 | if host, port, err = net.SplitHostPort(target + ":" + defaultPort); err == nil { |
| 382 | // target doesn't have port |
| 383 | return host, port, nil |
| 384 | } |
| 385 | return "", "", fmt.Errorf("invalid target address %v, error info: %v", target, err) |
| 386 | } |
| 387 | |
| 388 | type rawChoice struct { |
| 389 | ClientLanguage *[]string `json:"clientLanguage,omitempty"` |
| 390 | Percentage *int `json:"percentage,omitempty"` |
| 391 | ClientHostName *[]string `json:"clientHostName,omitempty"` |
| 392 | ServiceConfig *json.RawMessage `json:"serviceConfig,omitempty"` |
| 393 | } |
| 394 | |
| 395 | func containsString(a *[]string, b string) bool { |
| 396 | if a == nil { |
| 397 | return true |
| 398 | } |
| 399 | for _, c := range *a { |
| 400 | if c == b { |
| 401 | return true |
| 402 | } |
| 403 | } |
| 404 | return false |
| 405 | } |
| 406 | |
| 407 | func chosenByPercentage(a *int) bool { |
| 408 | if a == nil { |
| 409 | return true |
| 410 | } |
| 411 | return grpcrand.Intn(100)+1 <= *a |
| 412 | } |
| 413 | |
| 414 | func canaryingSC(js string) string { |
| 415 | if js == "" { |
| 416 | return "" |
| 417 | } |
| 418 | var rcs []rawChoice |
| 419 | err := json.Unmarshal([]byte(js), &rcs) |
| 420 | if err != nil { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 421 | grpclog.Warningf("dns: error parsing service config json: %v", err) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 422 | return "" |
| 423 | } |
| 424 | cliHostname, err := os.Hostname() |
| 425 | if err != nil { |
Arjun E K | 57a7fcb | 2020-01-30 06:44:45 +0000 | [diff] [blame] | 426 | grpclog.Warningf("dns: error getting client hostname: %v", err) |
Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 427 | return "" |
| 428 | } |
| 429 | var sc string |
| 430 | for _, c := range rcs { |
| 431 | if !containsString(c.ClientLanguage, golang) || |
| 432 | !chosenByPercentage(c.Percentage) || |
| 433 | !containsString(c.ClientHostName, cliHostname) || |
| 434 | c.ServiceConfig == nil { |
| 435 | continue |
| 436 | } |
| 437 | sc = string(*c.ServiceConfig) |
| 438 | break |
| 439 | } |
| 440 | return sc |
| 441 | } |