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-rw-r--r--vendor/google.golang.org/grpc/naming/dns_resolver.go293
1 files changed, 293 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..fd8cd3b5a
--- /dev/null
+++ b/vendor/google.golang.org/grpc/naming/dns_resolver.go
@@ -0,0 +1,293 @@
+/*
+ *
+ * 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 (
+ "context"
+ "errors"
+ "fmt"
+ "net"
+ "strconv"
+ "time"
+
+ "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")
+
+ lookupHost = net.DefaultResolver.LookupHost
+ lookupSRV = net.DefaultResolver.LookupSRV
+)
+
+// 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()
+}