xds, pickfirst: Enable additional addresses in xDS, set new pick_first as default (grpc#8126)

Author: arjan-bal

.github/workflows/coverage.yml

@@ -19,8 +19,8 @@ jobs:
       - name: Run coverage
         run: go test -coverprofile=coverage.out -coverpkg=./... ./...
 
-      - name: Run coverage with new pickfirst
-        run: GRPC_EXPERIMENTAL_ENABLE_NEW_PICK_FIRST=true go test -coverprofile=coverage_new_pickfirst.out -coverpkg=./... ./...
+      - name: Run coverage with old pickfirst
+        run: GRPC_EXPERIMENTAL_ENABLE_NEW_PICK_FIRST=false go test -coverprofile=coverage_old_pickfirst.out -coverpkg=./... ./...
 
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@v4

internal/envconfig/envconfig.go

@@ -51,10 +51,10 @@ var (
 	// xDS server in the list of server configs will be used.
 	XDSFallbackSupport = boolFromEnv("GRPC_EXPERIMENTAL_XDS_FALLBACK", true)
 	// NewPickFirstEnabled is set if the new pickfirst leaf policy is to be used
-	// instead of the exiting pickfirst implementation. This can be enabled by
+	// instead of the exiting pickfirst implementation. This can be disabled by
 	// setting the environment variable "GRPC_EXPERIMENTAL_ENABLE_NEW_PICK_FIRST"
-	// to "true".
-	NewPickFirstEnabled = boolFromEnv("GRPC_EXPERIMENTAL_ENABLE_NEW_PICK_FIRST", false)
+	// to "false".
+	NewPickFirstEnabled = boolFromEnv("GRPC_EXPERIMENTAL_ENABLE_NEW_PICK_FIRST", true)
 )
 
 func boolFromEnv(envVar string, def bool) bool {

internal/envconfig/xds.go

@@ -56,7 +56,7 @@ var (
 
 	// XDSDualstackEndpointsEnabled is true if gRPC should read the
 	// "additional addresses" in the xDS endpoint resource.
-	XDSDualstackEndpointsEnabled = boolFromEnv("GRPC_EXPERIMENTAL_XDS_DUALSTACK_ENDPOINTS", false)
+	XDSDualstackEndpointsEnabled = boolFromEnv("GRPC_EXPERIMENTAL_XDS_DUALSTACK_ENDPOINTS", true)
 
 	// XDSSystemRootCertsEnabled is true when xDS enabled gRPC clients can use
 	// the system's default root certificates for TLS certificate validation.