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author | JoramWilander <jwawilander@gmail.com> | 2018-07-10 15:01:43 -0400 |
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committer | JoramWilander <jwawilander@gmail.com> | 2018-07-10 15:01:43 -0400 |
commit | 6c7dc2d29ccac5f9925402f6be1a4c2a3c46c005 (patch) | |
tree | 5564a47257bf6e85aaef711980c5b0fcb4d07dcc /vendor/google.golang.org/grpc/naming/dns_resolver.go | |
parent | c042ffa460296587579aff54b157a5109e022f7e (diff) | |
parent | 1e1a5e5e85240f25c4faddcb24c5a29a915fe6e4 (diff) | |
download | chat-6c7dc2d29ccac5f9925402f6be1a4c2a3c46c005.tar.gz chat-6c7dc2d29ccac5f9925402f6be1a4c2a3c46c005.tar.bz2 chat-6c7dc2d29ccac5f9925402f6be1a4c2a3c46c005.zip |
Merge branch 'plugins-2'
Diffstat (limited to 'vendor/google.golang.org/grpc/naming/dns_resolver.go')
-rw-r--r-- | vendor/google.golang.org/grpc/naming/dns_resolver.go | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/vendor/google.golang.org/grpc/naming/dns_resolver.go b/vendor/google.golang.org/grpc/naming/dns_resolver.go new file mode 100644 index 000000000..0f8a908ea --- /dev/null +++ b/vendor/google.golang.org/grpc/naming/dns_resolver.go @@ -0,0 +1,290 @@ +/* + * + * Copyright 2017 gRPC authors. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + * + */ + +package naming + +import ( + "errors" + "fmt" + "net" + "strconv" + "time" + + "golang.org/x/net/context" + "google.golang.org/grpc/grpclog" +) + +const ( + defaultPort = "443" + defaultFreq = time.Minute * 30 +) + +var ( + errMissingAddr = errors.New("missing address") + errWatcherClose = errors.New("watcher has been closed") +) + +// NewDNSResolverWithFreq creates a DNS Resolver that can resolve DNS names, and +// create watchers that poll the DNS server using the frequency set by freq. +func NewDNSResolverWithFreq(freq time.Duration) (Resolver, error) { + return &dnsResolver{freq: freq}, nil +} + +// NewDNSResolver creates a DNS Resolver that can resolve DNS names, and create +// watchers that poll the DNS server using the default frequency defined by defaultFreq. +func NewDNSResolver() (Resolver, error) { + return NewDNSResolverWithFreq(defaultFreq) +} + +// dnsResolver handles name resolution for names following the DNS scheme +type dnsResolver struct { + // frequency of polling the DNS server that the watchers created by this resolver will use. + freq time.Duration +} + +// formatIP returns ok = false if addr is not a valid textual representation of an IP address. +// If addr is an IPv4 address, return the addr and ok = true. +// If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true. +func formatIP(addr string) (addrIP string, ok bool) { + ip := net.ParseIP(addr) + if ip == nil { + return "", false + } + if ip.To4() != nil { + return addr, true + } + return "[" + addr + "]", true +} + +// parseTarget takes the user input target string, returns formatted host and port info. +// If target doesn't specify a port, set the port to be the defaultPort. +// If target is in IPv6 format and host-name is enclosed in sqarue brackets, brackets +// are strippd when setting the host. +// examples: +// target: "www.google.com" returns host: "www.google.com", port: "443" +// target: "ipv4-host:80" returns host: "ipv4-host", port: "80" +// target: "[ipv6-host]" returns host: "ipv6-host", port: "443" +// target: ":80" returns host: "localhost", port: "80" +// target: ":" returns host: "localhost", port: "443" +func parseTarget(target string) (host, port string, err error) { + if target == "" { + return "", "", errMissingAddr + } + + if ip := net.ParseIP(target); ip != nil { + // target is an IPv4 or IPv6(without brackets) address + return target, defaultPort, nil + } + if host, port, err := net.SplitHostPort(target); err == nil { + // target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port + if host == "" { + // Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed. + host = "localhost" + } + if port == "" { + // If the port field is empty(target ends with colon), e.g. "[::1]:", defaultPort is used. + port = defaultPort + } + return host, port, nil + } + if host, port, err := net.SplitHostPort(target + ":" + defaultPort); err == nil { + // target doesn't have port + return host, port, nil + } + return "", "", fmt.Errorf("invalid target address %v", target) +} + +// Resolve creates a watcher that watches the name resolution of the target. +func (r *dnsResolver) Resolve(target string) (Watcher, error) { + host, port, err := parseTarget(target) + if err != nil { + return nil, err + } + + if net.ParseIP(host) != nil { + ipWatcher := &ipWatcher{ + updateChan: make(chan *Update, 1), + } + host, _ = formatIP(host) + ipWatcher.updateChan <- &Update{Op: Add, Addr: host + ":" + port} + return ipWatcher, nil + } + + ctx, cancel := context.WithCancel(context.Background()) + return &dnsWatcher{ + r: r, + host: host, + port: port, + ctx: ctx, + cancel: cancel, + t: time.NewTimer(0), + }, nil +} + +// dnsWatcher watches for the name resolution update for a specific target +type dnsWatcher struct { + r *dnsResolver + host string + port string + // The latest resolved address set + curAddrs map[string]*Update + ctx context.Context + cancel context.CancelFunc + t *time.Timer +} + +// ipWatcher watches for the name resolution update for an IP address. +type ipWatcher struct { + updateChan chan *Update +} + +// Next returns the address resolution Update for the target. For IP address, +// the resolution is itself, thus polling name server is unnecessary. Therefore, +// Next() will return an Update the first time it is called, and will be blocked +// for all following calls as no Update exists until watcher is closed. +func (i *ipWatcher) Next() ([]*Update, error) { + u, ok := <-i.updateChan + if !ok { + return nil, errWatcherClose + } + return []*Update{u}, nil +} + +// Close closes the ipWatcher. +func (i *ipWatcher) Close() { + close(i.updateChan) +} + +// AddressType indicates the address type returned by name resolution. +type AddressType uint8 + +const ( + // Backend indicates the server is a backend server. + Backend AddressType = iota + // GRPCLB indicates the server is a grpclb load balancer. + GRPCLB +) + +// AddrMetadataGRPCLB contains the information the name resolver for grpclb should provide. The +// name resolver used by the grpclb balancer is required to provide this type of metadata in +// its address updates. +type AddrMetadataGRPCLB struct { + // AddrType is the type of server (grpc load balancer or backend). + AddrType AddressType + // ServerName is the name of the grpc load balancer. Used for authentication. + ServerName string +} + +// compileUpdate compares the old resolved addresses and newly resolved addresses, +// and generates an update list +func (w *dnsWatcher) compileUpdate(newAddrs map[string]*Update) []*Update { + var res []*Update + for a, u := range w.curAddrs { + if _, ok := newAddrs[a]; !ok { + u.Op = Delete + res = append(res, u) + } + } + for a, u := range newAddrs { + if _, ok := w.curAddrs[a]; !ok { + res = append(res, u) + } + } + return res +} + +func (w *dnsWatcher) lookupSRV() map[string]*Update { + newAddrs := make(map[string]*Update) + _, srvs, err := lookupSRV(w.ctx, "grpclb", "tcp", w.host) + if err != nil { + grpclog.Infof("grpc: failed dns SRV record lookup due to %v.\n", err) + return nil + } + for _, s := range srvs { + lbAddrs, err := lookupHost(w.ctx, s.Target) + if err != nil { + grpclog.Warningf("grpc: failed load banlacer address dns lookup due to %v.\n", err) + continue + } + for _, a := range lbAddrs { + a, ok := formatIP(a) + if !ok { + grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err) + continue + } + addr := a + ":" + strconv.Itoa(int(s.Port)) + newAddrs[addr] = &Update{Addr: addr, + Metadata: AddrMetadataGRPCLB{AddrType: GRPCLB, ServerName: s.Target}} + } + } + return newAddrs +} + +func (w *dnsWatcher) lookupHost() map[string]*Update { + newAddrs := make(map[string]*Update) + addrs, err := lookupHost(w.ctx, w.host) + if err != nil { + grpclog.Warningf("grpc: failed dns A record lookup due to %v.\n", err) + return nil + } + for _, a := range addrs { + a, ok := formatIP(a) + if !ok { + grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err) + continue + } + addr := a + ":" + w.port + newAddrs[addr] = &Update{Addr: addr} + } + return newAddrs +} + +func (w *dnsWatcher) lookup() []*Update { + newAddrs := w.lookupSRV() + if newAddrs == nil { + // If failed to get any balancer address (either no corresponding SRV for the + // target, or caused by failure during resolution/parsing of the balancer target), + // return any A record info available. + newAddrs = w.lookupHost() + } + result := w.compileUpdate(newAddrs) + w.curAddrs = newAddrs + return result +} + +// Next returns the resolved address update(delta) for the target. If there's no +// change, it will sleep for 30 mins and try to resolve again after that. +func (w *dnsWatcher) Next() ([]*Update, error) { + for { + select { + case <-w.ctx.Done(): + return nil, errWatcherClose + case <-w.t.C: + } + result := w.lookup() + // Next lookup should happen after an interval defined by w.r.freq. + w.t.Reset(w.r.freq) + if len(result) > 0 { + return result, nil + } + } +} + +func (w *dnsWatcher) Close() { + w.cancel() +} |