AUTH-2105: Adds support for local forwarding. Refactor auditlogger creation.

AUTH-2088: Adds dynamic destination routing

vendor/google.golang.org/grpc/resolver/dns/dns_resolver.go

@@ -66,6 +66,9 @@ var (
 
 var (
 	defaultResolver netResolver = net.DefaultResolver
+	// To prevent excessive re-resolution, we enforce a rate limit on DNS
+	// resolution requests.
+	minDNSResRate = 30 * time.Second
 )
 
 var customAuthorityDialler = func(authority string) func(ctx context.Context, network, address string) (net.Conn, error) {
@@ -241,7 +244,13 @@ func (d *dnsResolver) watcher() {
 			return
 		case <-d.t.C:
 		case <-d.rn:
+			if !d.t.Stop() {
+				// Before resetting a timer, it should be stopped to prevent racing with
+				// reads on it's channel.
+				<-d.t.C
+			}
 		}
+
 		result, sc := d.lookup()
 		// Next lookup should happen within an interval defined by d.freq. It may be
 		// more often due to exponential retry on empty address list.
@@ -254,6 +263,16 @@ func (d *dnsResolver) watcher() {
 		}
 		d.cc.NewServiceConfig(sc)
 		d.cc.NewAddress(result)
+
+		// Sleep to prevent excessive re-resolutions. Incoming resolution requests
+		// will be queued in d.rn.
+		t := time.NewTimer(minDNSResRate)
+		select {
+		case <-t.C:
+		case <-d.ctx.Done():
+			t.Stop()
+			return
+		}
 	}
 }
 

vendor/google.golang.org/grpc/resolver/resolver.go

@@ -20,6 +20,10 @@
 // All APIs in this package are experimental.
 package resolver
 
+import (
+	"google.golang.org/grpc/serviceconfig"
+)
+
 var (
 	// m is a map from scheme to resolver builder.
 	m = make(map[string]Builder)
@@ -100,11 +104,12 @@ type BuildOption struct {
 
 // State contains the current Resolver state relevant to the ClientConn.
 type State struct {
-	Addresses     []Address // Resolved addresses for the target
-	ServiceConfig string    // JSON representation of the service config
+	Addresses []Address // Resolved addresses for the target
+	// ServiceConfig is the parsed service config; obtained from
+	// serviceconfig.Parse.
+	ServiceConfig serviceconfig.Config
 
 	// TODO: add Err error
-	// TODO: add ParsedServiceConfig interface{}
 }
 
 // ClientConn contains the callbacks for resolver to notify any updates
@@ -132,6 +137,21 @@ type ClientConn interface {
 
 // Target represents a target for gRPC, as specified in:
 // https://github.com/grpc/grpc/blob/master/doc/naming.md.
+// It is parsed from the target string that gets passed into Dial or DialContext by the user. And
+// grpc passes it to the resolver and the balancer.
+//
+// If the target follows the naming spec, and the parsed scheme is registered with grpc, we will
+// parse the target string according to the spec. e.g. "dns://some_authority/foo.bar" will be parsed
+// into &Target{Scheme: "dns", Authority: "some_authority", Endpoint: "foo.bar"}
+//
+// If the target does not contain a scheme, we will apply the default scheme, and set the Target to
+// be the full target string. e.g. "foo.bar" will be parsed into
+// &Target{Scheme: resolver.GetDefaultScheme(), Endpoint: "foo.bar"}.
+//
+// If the parsed scheme is not registered (i.e. no corresponding resolver available to resolve the
+// endpoint), we set the Scheme to be the default scheme, and set the Endpoint to be the full target
+// string. e.g. target string "unknown_scheme://authority/endpoint" will be parsed into
+// &Target{Scheme: resolver.GetDefaultScheme(), Endpoint: "unknown_scheme://authority/endpoint"}.
 type Target struct {
 	Scheme    string
 	Authority string