Implementation of the xds_experimental resolver.

This resolver doesn't do much at this point, except returning an empty
address list and a hard-coded service config which picks the xds
balancer with a round_robin child policy.

Also moved the xdsConfig struct to the xds/internal package and exported
it as LBConfig, so that both the resolver and the balancer packages can
make use of this.

vet.sh

@@ -111,6 +111,7 @@ google.golang.org/grpc/balancer.go:SA1019
 google.golang.org/grpc/balancer/grpclb/grpclb_remote_balancer.go:SA1019
 google.golang.org/grpc/balancer/roundrobin/roundrobin_test.go:SA1019
 google.golang.org/grpc/xds/internal/balancer/edsbalancer/balancergroup.go:SA1019
+google.golang.org/grpc/xds/internal/resolver/xds_resolver.go:SA1019
 google.golang.org/grpc/xds/internal/balancer/xds.go:SA1019
 google.golang.org/grpc/xds/internal/balancer/xds_client.go:SA1019
 google.golang.org/grpc/balancer_conn_wrappers.go:SA1019

xds/experimental/xds_experimental.go

@@ -24,9 +24,12 @@ package experimental
 
 import (
 	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/resolver"
 	xdsbalancer "google.golang.org/grpc/xds/internal/balancer"
+	xdsresolver "google.golang.org/grpc/xds/internal/resolver"
 )
 
 func init() {
+	resolver.Register(xdsresolver.NewBuilder())
 	balancer.Register(xdsbalancer.NewBalancerBuilder())
 }

xds/internal/balancer/xds.go

@@ -33,16 +33,14 @@ import (
 	"google.golang.org/grpc/grpclog"
 	"google.golang.org/grpc/resolver"
 	"google.golang.org/grpc/serviceconfig"
+	xdsinternal "google.golang.org/grpc/xds/internal"
 	"google.golang.org/grpc/xds/internal/balancer/edsbalancer"
 	"google.golang.org/grpc/xds/internal/balancer/lrs"
 	cdspb "google.golang.org/grpc/xds/internal/proto/envoy/api/v2/cds"
 	edspb "google.golang.org/grpc/xds/internal/proto/envoy/api/v2/eds"
 )
 
-const (
-	defaultTimeout = 10 * time.Second
-	xdsName        = "xds_experimental"
-)
+const defaultTimeout = 10 * time.Second
 
 var (
 	// This field is for testing purpose.
@@ -85,11 +83,11 @@ func (b *xdsBalancerBuilder) Build(cc balancer.ClientConn, opts balancer.BuildOp
 }
 
 func (b *xdsBalancerBuilder) Name() string {
-	return xdsName
+	return xdsinternal.ExperimentalName
 }
 
 func (b *xdsBalancerBuilder) ParseConfig(c json.RawMessage) (serviceconfig.LoadBalancingConfig, error) {
-	var cfg xdsConfig
+	var cfg xdsinternal.LBConfig
 	if err := json.Unmarshal(c, &cfg); err != nil {
 		return nil, fmt.Errorf("unable to unmarshal balancer config %s into xds config", string(c))
 	}
@@ -130,15 +128,15 @@ type xdsBalancer struct {
 	timer           *time.Timer
 	noSubConnAlert  <-chan struct{}
 
-	client           *client    // may change when passed a different service config
-	config           *xdsConfig // may change when passed a different service config
+	client           *client               // may change when passed a different service config
+	config           *xdsinternal.LBConfig // may change when passed a different service config
 	xdsLB            edsBalancerInterface
 	fallbackLB       balancer.Balancer
 	fallbackInitData *resolver.State // may change when HandleResolved address is called
 	loadStore        lrs.Store
 }
 
-func (x *xdsBalancer) startNewXDSClient(u *xdsConfig) {
+func (x *xdsBalancer) startNewXDSClient(u *xdsinternal.LBConfig) {
 	// If the xdsBalancer is in startup stage, then we need to apply the startup timeout for the first
 	// xdsClient to get a response from the traffic director.
 	if x.startup {
@@ -237,7 +235,7 @@ func (x *xdsBalancer) handleGRPCUpdate(update interface{}) {
 			}
 		}
 	case *balancer.ClientConnState:
-		cfg, _ := u.BalancerConfig.(*xdsConfig)
+		cfg, _ := u.BalancerConfig.(*xdsinternal.LBConfig)
 		if cfg == nil {
 			// service config parsing failed. should never happen.
 			return
@@ -497,16 +495,16 @@ func (x *xdsBalancer) cancelFallbackAndSwitchEDSBalancerIfNecessary() {
 	}
 }
 
-func (x *xdsBalancer) buildFallBackBalancer(c *xdsConfig) {
+func (x *xdsBalancer) buildFallBackBalancer(c *xdsinternal.LBConfig) {
 	if c.FallBackPolicy == nil {
-		x.buildFallBackBalancer(&xdsConfig{
-			FallBackPolicy: &loadBalancingConfig{
+		x.buildFallBackBalancer(&xdsinternal.LBConfig{
+			FallBackPolicy: &xdsinternal.LoadBalancingConfig{
 				Name: "round_robin",
 			},
 		})
 		return
 	}
-	// builder will always be non-nil, since when parse JSON into xdsConfig, we check whether the specified
+	// builder will always be non-nil, since when parse JSON into xdsinternal.LBConfig, we check whether the specified
 	// balancer is registered or not.
 	builder := balancer.Get(c.FallBackPolicy.Name)
 
@@ -566,77 +564,3 @@ func createDrainedTimer() *time.Timer {
 	}
 	return timer
 }
-
-type xdsConfig struct {
-	serviceconfig.LoadBalancingConfig
-	BalancerName   string
-	ChildPolicy    *loadBalancingConfig
-	FallBackPolicy *loadBalancingConfig
-}
-
-// When unmarshalling json to xdsConfig, we iterate through the childPolicy/fallbackPolicy lists
-// and select the first LB policy which has been registered to be stored in the returned xdsConfig.
-func (p *xdsConfig) UnmarshalJSON(data []byte) error {
-	var val map[string]json.RawMessage
-	if err := json.Unmarshal(data, &val); err != nil {
-		return err
-	}
-	for k, v := range val {
-		switch k {
-		case "balancerName":
-			if err := json.Unmarshal(v, &p.BalancerName); err != nil {
-				return err
-			}
-		case "childPolicy":
-			var lbcfgs []*loadBalancingConfig
-			if err := json.Unmarshal(v, &lbcfgs); err != nil {
-				return err
-			}
-			for _, lbcfg := range lbcfgs {
-				if balancer.Get(lbcfg.Name) != nil {
-					p.ChildPolicy = lbcfg
-					break
-				}
-			}
-		case "fallbackPolicy":
-			var lbcfgs []*loadBalancingConfig
-			if err := json.Unmarshal(v, &lbcfgs); err != nil {
-				return err
-			}
-			for _, lbcfg := range lbcfgs {
-				if balancer.Get(lbcfg.Name) != nil {
-					p.FallBackPolicy = lbcfg
-					break
-				}
-			}
-		}
-	}
-	return nil
-}
-
-func (p *xdsConfig) MarshalJSON() ([]byte, error) {
-	return nil, nil
-}
-
-type loadBalancingConfig struct {
-	Name   string
-	Config json.RawMessage
-}
-
-func (l *loadBalancingConfig) MarshalJSON() ([]byte, error) {
-	m := make(map[string]json.RawMessage)
-	m[l.Name] = l.Config
-	return json.Marshal(m)
-}
-
-func (l *loadBalancingConfig) UnmarshalJSON(data []byte) error {
-	var cfg map[string]json.RawMessage
-	if err := json.Unmarshal(data, &cfg); err != nil {
-		return err
-	}
-	for name, config := range cfg {
-		l.Name = name
-		l.Config = config
-	}
-	return nil
-}

xds/internal/balancer/xds_lrs_test.go

@@ -33,6 +33,7 @@ import (
 	"google.golang.org/grpc/resolver"
 	"google.golang.org/grpc/status"
 	"google.golang.org/grpc/xds/internal"
+	xdsinternal "google.golang.org/grpc/xds/internal"
 	basepb "google.golang.org/grpc/xds/internal/proto/envoy/api/v2/core/base"
 	lrsgrpc "google.golang.org/grpc/xds/internal/proto/envoy/service/load_stats/v2/lrs"
 	lrspb "google.golang.org/grpc/xds/internal/proto/envoy/service/load_stats/v2/lrs"
@@ -95,7 +96,7 @@ func (s) TestXdsLoadReporting(t *testing.T) {
 		newEDSBalancer = originalNewEDSBalancer
 	}()
 
-	builder := balancer.Get(xdsName)
+	builder := balancer.Get(xdsinternal.ExperimentalName)
 	cc := newTestClientConn()
 	lb, ok := builder.Build(cc, balancer.BuildOptions{Target: resolver.Target{Endpoint: testServiceName}}).(*xdsBalancer)
 	if !ok {
@@ -112,9 +113,9 @@ func (s) TestXdsLoadReporting(t *testing.T) {
 		Nanos:   intervalNano,
 	}
 
-	cfg := &xdsConfig{
+	cfg := &xdsinternal.LBConfig{
 		BalancerName: addr,
-		ChildPolicy:  &loadBalancingConfig{Name: fakeBalancerA}, // Set this to skip cds.
+		ChildPolicy:  &xdsinternal.LoadBalancingConfig{Name: fakeBalancerA}, // Set this to skip cds.
 	}
 	lb.UpdateClientConnState(balancer.ClientConnState{BalancerConfig: cfg})
 	td.sendResp(&response{resp: testEDSRespWithoutEndpoints})