xds: add support for multiple xDS clients, for fallback (#7347)

internal/testutils/xds/e2e/logging.go

@@ -27,14 +27,14 @@ type serverLogger struct {
 }
 
 func (l serverLogger) Debugf(format string, args ...any) {
-	l.logger.Logf(format, args)
+	l.logger.Logf(format, args...)
 }
 func (l serverLogger) Infof(format string, args ...any) {
-	l.logger.Logf(format, args)
+	l.logger.Logf(format, args...)
 }
 func (l serverLogger) Warnf(format string, args ...any) {
-	l.logger.Logf(format, args)
+	l.logger.Logf(format, args...)
 }
 func (l serverLogger) Errorf(format string, args ...any) {
-	l.logger.Logf(format, args)
+	l.logger.Logf(format, args...)
 }

internal/xds/bootstrap/bootstrap.go

@@ -34,7 +34,6 @@ import (
 	"google.golang.org/grpc/credentials/tls/certprovider"
 	"google.golang.org/grpc/internal"
 	"google.golang.org/grpc/internal/envconfig"
-	"google.golang.org/grpc/internal/pretty"
 	"google.golang.org/grpc/xds/bootstrap"
 	"google.golang.org/protobuf/proto"
 	"google.golang.org/protobuf/types/known/structpb"
@@ -213,6 +212,9 @@ func (sc *ServerConfig) Equal(other *ServerConfig) bool {
 // content. It doesn't cover NodeProto because NodeProto isn't used by
 // federation.
 func (sc *ServerConfig) String() string {
+	if len(sc.serverFeatures) == 0 {
+		return fmt.Sprintf("%s-%s", sc.serverURI, sc.selectedCreds.String())
+	}
 	features := strings.Join(sc.serverFeatures, "-")
 	return strings.Join([]string{sc.serverURI, sc.selectedCreds.String(), features}, "-")
 }
@@ -418,6 +420,12 @@ func (c *Config) Equal(other *Config) bool {
 	return true
 }
 
+// String returns a string representation of the Config.
+func (c *Config) String() string {
+	s, _ := c.MarshalJSON()
+	return string(s)
+}
+
 // The following fields correspond 1:1 with the JSON schema for Config.
 type configJSON struct {
 	XDSServers                                []*ServerConfig                      `json:"xds_servers,omitempty"`
@@ -438,7 +446,7 @@ func (c *Config) MarshalJSON() ([]byte, error) {
 		Authorities:                               c.authorities,
 		Node:                                      c.node,
 	}
-	return json.Marshal(config)
+	return json.MarshalIndent(config, " ", " ")
 }
 
 // UnmarshalJSON takes the json data (the complete bootstrap configuration) and
@@ -566,9 +574,7 @@ func newConfigFromContents(data []byte) (*Config, error) {
 	}
 
 	if logger.V(2) {
-		logger.Infof("Bootstrap config for creating xds-client: %v", pretty.ToJSON(config))
-	} else {
-		logger.Infof("Bootstrap config for creating xds-client: %+v", config)
+		logger.Infof("Bootstrap config for creating xds-client: %s", config)
 	}
 	return config, nil
 }
@@ -632,7 +638,7 @@ func NewContentsForTesting(opts ConfigOptionsForTesting) ([]byte, error) {
 		Authorities:                               authorities,
 		Node:                                      node{ID: opts.NodeID},
 	}
-	contents, err := json.Marshal(cfgJSON)
+	contents, err := json.MarshalIndent(cfgJSON, " ", " ")
 	if err != nil {
 		return nil, fmt.Errorf("failed to marshal bootstrap configuration for provided options %+v: %v", opts, err)
 	}

xds/csds/csds.go

@@ -27,7 +27,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"sync"
 
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/grpclog"
@@ -55,22 +54,14 @@ func prefixLogger(s *ClientStatusDiscoveryServer) *internalgrpclog.PrefixLogger
 // https://github.com/grpc/proposal/blob/master/A40-csds-support.md.
 type ClientStatusDiscoveryServer struct {
 	logger *internalgrpclog.PrefixLogger
-
-	mu             sync.Mutex
-	xdsClient      xdsclient.XDSClient
-	xdsClientClose func()
 }
 
 // NewClientStatusDiscoveryServer returns an implementation of the CSDS server
 // that can be registered on a gRPC server.
 func NewClientStatusDiscoveryServer() (*ClientStatusDiscoveryServer, error) {
-	c, close, err := xdsclient.New()
-	if err != nil {
-		logger.Warningf("Failed to create xDS client: %v", err)
-	}
-	s := &ClientStatusDiscoveryServer{xdsClient: c, xdsClientClose: close}
+	s := &ClientStatusDiscoveryServer{}
 	s.logger = prefixLogger(s)
-	s.logger.Infof("Created CSDS server, with xdsClient %p", c)
+	s.logger.Infof("Created CSDS server")
 	return s, nil
 }
 
@@ -104,24 +95,14 @@ func (s *ClientStatusDiscoveryServer) FetchClientStatus(_ context.Context, req *
 //
 // If it returns an error, the error is a status error.
 func (s *ClientStatusDiscoveryServer) buildClientStatusRespForReq(req *v3statuspb.ClientStatusRequest) (*v3statuspb.ClientStatusResponse, error) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-
-	if s.xdsClient == nil {
-		return &v3statuspb.ClientStatusResponse{}, nil
-	}
 	// Field NodeMatchers is unsupported, by design
 	// https://github.com/grpc/proposal/blob/master/A40-csds-support.md#detail-node-matching.
 	if len(req.NodeMatchers) != 0 {
 		return nil, status.Errorf(codes.InvalidArgument, "node_matchers are not supported, request contains node_matchers: %v", req.NodeMatchers)
 	}
 
-	return s.xdsClient.DumpResources()
+	return xdsclient.DumpResources(), nil
 }
 
 // Close cleans up the resources.
-func (s *ClientStatusDiscoveryServer) Close() {
-	if s.xdsClientClose != nil {
-		s.xdsClientClose()
-	}
-}
+func (s *ClientStatusDiscoveryServer) Close() {}