[xds] Remove variable protection from custom LB policies (#32888)

doc/grpc_xds_features.md

@@ -68,4 +68,4 @@ Support for [xDS v2 APIs](https://www.envoyproxy.io/docs/envoy/latest/api/api_su
 [Security](https://www.envoyproxy.io/docs/envoy/latest/configuration/security/security):<br>Uses [certificate providers](https://github.com/grpc/proposal/blob/master/A29-xds-tls-security.md#certificate-provider-plugin-framework) instead of SDS | [A29](https://github.com/grpc/proposal/blob/master/A29-xds-tls-security.md) | v1.41.0<br>(C++ and Python) | v1.41.0 | 1.41.0 | |
 [Authorization (RBAC)](https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/filters/http/rbac/v3/rbac.proto):<br><ul><li>`LOG` action has no effect<li>CEL unsupported and rejected</ul> | [A41](https://github.com/grpc/proposal/blob/master/A41-xds-rbac.md) | v1.51.0<br>(C++ and Python) | v1.42.0 | 1.42.0 | |
 [Outlier Detection](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/upstream/outlier):<br>Only the following detection types are supported:<ul><li>Success Rate</li><li>Failure Percentage</li></ul> | [A50](https://github.com/grpc/proposal/blob/master/A50-xds-outlier-detection.md) | v1.51.0 | v1.49.0 | v1.50.0 | v1.7.0 | |
-[Custom Load Balancer Configuration](https://github.com/envoyproxy/envoy/blob/57be3189ffa3372b34e9480d1f02b2d165e49077/api/envoy/config/cluster/v3/cluster.proto#L1208)<br> | [A52](https://github.com/grpc/proposal/blob/master/A52-xds-custom-lb-policies.md) | | v1.47.0 | | |
+[Custom Load Balancer Configuration](https://github.com/envoyproxy/envoy/blob/57be3189ffa3372b34e9480d1f02b2d165e49077/api/envoy/config/cluster/v3/cluster.proto#L1208)<br> | [A52](https://github.com/grpc/proposal/blob/master/A52-xds-custom-lb-policies.md) | v1.55.0 | v1.47.0 | | |

src/core/ext/xds/xds_cluster.cc

@@ -68,15 +68,6 @@
 
 namespace grpc_core {
 
-// TODO(roth): Remove once custom LB policy support is no longer experimental.
-bool XdsCustomLbPolicyEnabled() {
-  auto value = GetEnv("GRPC_EXPERIMENTAL_XDS_CUSTOM_LB_CONFIG");
-  if (!value.has_value()) return false;
-  bool parsed_value;
-  bool parse_succeeded = gpr_parse_bool_value(value->c_str(), &parsed_value);
-  return parse_succeeded && parsed_value;
-}
-
 // TODO(eostroukhov): Remove once this feature is no longer experimental.
 bool XdsOverrideHostEnabled() {
   auto value = GetEnv("GRPC_EXPERIMENTAL_XDS_ENABLE_OVERRIDE_HOST");
@@ -323,28 +314,25 @@ void ParseLbPolicyConfig(const XdsResourceType::DecodeContext& context,
                          XdsClusterResource* cds_update,
                          ValidationErrors* errors) {
   // First, check the new load_balancing_policy field.
-  if (XdsCustomLbPolicyEnabled()) {
-    const auto* load_balancing_policy =
-        envoy_config_cluster_v3_Cluster_load_balancing_policy(cluster);
-    if (load_balancing_policy != nullptr) {
-      const auto& registry =
-          static_cast<const GrpcXdsBootstrap&>(context.client->bootstrap())
-              .lb_policy_registry();
-      ValidationErrors::ScopedField field(errors, ".load_balancing_policy");
-      const size_t original_error_count = errors->size();
-      cds_update->lb_policy_config = registry.ConvertXdsLbPolicyConfig(
-          context, load_balancing_policy, errors);
-      // If there were no conversion errors, validate that the converted config
-      // parses with the gRPC LB policy registry.
-      if (original_error_count == errors->size()) {
-        auto config =
-            CoreConfiguration::Get()
-                .lb_policy_registry()
-                .ParseLoadBalancingConfig(cds_update->lb_policy_config);
-        if (!config.ok()) errors->AddError(config.status().message());
-      }
-      return;
+  const auto* load_balancing_policy =
+      envoy_config_cluster_v3_Cluster_load_balancing_policy(cluster);
+  if (load_balancing_policy != nullptr) {
+    const auto& registry =
+        static_cast<const GrpcXdsBootstrap&>(context.client->bootstrap())
+            .lb_policy_registry();
+    ValidationErrors::ScopedField field(errors, ".load_balancing_policy");
+    const size_t original_error_count = errors->size();
+    cds_update->lb_policy_config = registry.ConvertXdsLbPolicyConfig(
+        context, load_balancing_policy, errors);
+    // If there were no conversion errors, validate that the converted config
+    // parses with the gRPC LB policy registry.
+    if (original_error_count == errors->size()) {
+      auto config = CoreConfiguration::Get()
+                        .lb_policy_registry()
+                        .ParseLoadBalancingConfig(cds_update->lb_policy_config);
+      if (!config.ok()) errors->AddError(config.status().message());
     }
+    return;
   }
   // Didn't find load_balancing_policy field, so fall back to the old
   // lb_policy enum field.

src/core/ext/xds/xds_cluster.h

@@ -47,7 +47,6 @@
 
 namespace grpc_core {
 
-bool XdsCustomLbPolicyEnabled();
 bool XdsOverrideHostEnabled();
 
 struct XdsClusterResource : public XdsResourceType::ResourceData {

test/core/xds/xds_cluster_resource_type_test.cc

@@ -779,7 +779,6 @@ TEST_F(LbPolicyTest, EnumUnsupportedPolicy) {
 }
 
 TEST_F(LbPolicyTest, LoadBalancingPolicyField) {
-  ScopedExperimentalEnvVar env_var("GRPC_EXPERIMENTAL_XDS_CUSTOM_LB_CONFIG");
   Cluster cluster;
   cluster.set_name("foo");
   cluster.set_type(cluster.EDS);
@@ -810,38 +809,10 @@ TEST_F(LbPolicyTest, LoadBalancingPolicyField) {
             "\"childPolicy\":[{\"round_robin\":{}}]}}]");
 }
 
-TEST_F(LbPolicyTest, LoadBalancingPolicyFieldIgnoredUnlessEnabled) {
-  Cluster cluster;
-  cluster.set_name("foo");
-  cluster.set_type(cluster.EDS);
-  cluster.mutable_eds_cluster_config()->mutable_eds_config()->mutable_self();
-  // New field says to use round_robin, but the old enum field says to use
-  // ring_hash.  The env var is not enabled, so we use the old enum field.
-  cluster.mutable_load_balancing_policy()
-      ->add_policies()
-      ->mutable_typed_extension_config()
-      ->mutable_typed_config()
-      ->PackFrom(RoundRobin());
-  cluster.set_lb_policy(cluster.RING_HASH);
-  std::string serialized_resource;
-  ASSERT_TRUE(cluster.SerializeToString(&serialized_resource));
-  auto* resource_type = XdsClusterResourceType::Get();
-  auto decode_result =
-      resource_type->Decode(decode_context_, serialized_resource);
-  ASSERT_TRUE(decode_result.resource.ok()) << decode_result.resource.status();
-  ASSERT_TRUE(decode_result.name.has_value());
-  EXPECT_EQ(*decode_result.name, "foo");
-  auto& resource = static_cast<XdsClusterResource&>(**decode_result.resource);
-  EXPECT_EQ(JsonDump(Json{resource.lb_policy_config}),
-            "[{\"ring_hash_experimental\":{"
-            "\"maxRingSize\":8388608,\"minRingSize\":1024}}]");
-}
-
 // This tests that we're passing along errors from XdsLbPolicyRegistry.
 // A complete list of error cases for that class is in
 // xds_lb_policy_registry_test.
 TEST_F(LbPolicyTest, XdsLbPolicyRegistryConversionFails) {
-  ScopedExperimentalEnvVar env_var("GRPC_EXPERIMENTAL_XDS_CUSTOM_LB_CONFIG");
   Cluster cluster;
   cluster.set_name("foo");
   cluster.set_type(cluster.EDS);
@@ -870,7 +841,6 @@ TEST_F(LbPolicyTest, XdsLbPolicyRegistryConversionFails) {
 }
 
 TEST_F(LbPolicyTest, ConvertedCustomPolicyFailsValidation) {
-  ScopedExperimentalEnvVar env_var("GRPC_EXPERIMENTAL_XDS_CUSTOM_LB_CONFIG");
   Cluster cluster;
   cluster.set_name("foo");
   cluster.set_type(cluster.EDS);

test/cpp/end2end/xds/xds_wrr_end2end_test.cc

@@ -48,7 +48,6 @@ INSTANTIATE_TEST_SUITE_P(XdsTest, WrrTest, ::testing::Values(XdsTestType()),
                          &XdsTestType::Name);
 
 TEST_P(WrrTest, Basic) {
-  ScopedExperimentalEnvVar env_var1("GRPC_EXPERIMENTAL_XDS_CUSTOM_LB_CONFIG");
   ScopedExperimentalEnvVar env_var2("GRPC_EXPERIMENTAL_XDS_WRR_LB");
   CreateAndStartBackends(3);
   // Expected weights = qps / (cpu_util + (eps/qps)) =