Ensuring each action is only generated once in service config, even

if the same one is referred to multiple times by routes.

Added this test case in existing test case.

src/core/ext/filters/client_channel/xds/xds_client.cc

@@ -2068,10 +2068,14 @@ grpc_error* XdsClient::CreateServiceConfig(
       "    { \"xds_routing_experimental\":{\n"
       "      \"actions\":{\n");
   std::vector<std::string> actions_vector;
+  std::set<std::string> actions_set;
   for (size_t i = 0; i < rds_update.routes.size(); ++i) {
     auto route = rds_update.routes[i];
-    actions_vector.push_back(
+    if (actions_set.find(route.cluster_name) == actions_set.end()) {
-        CreateServiceConfigActionCluster(route.cluster_name.c_str()));
+      actions_vector.push_back(
+          CreateServiceConfigActionCluster(route.cluster_name.c_str()));
+      actions_set.emplace(route.cluster_name);
+    }
   }
   config_parts.push_back(absl::StrJoin(actions_vector, ",\n"));
   config_parts.push_back(

test/cpp/end2end/xds_end2end_test.cc

@@ -2576,6 +2576,9 @@ TEST_P(LdsTest, XdsRoutingPathMatching) {
   auto* route2 = new_route_config.mutable_virtual_hosts(0)->add_routes();
   route2->mutable_match()->set_path("/grpc.testing.EchoTest2Service/Echo2");
   route2->mutable_route()->set_cluster(kNewCluster2Name);
+  auto* route3 = new_route_config.mutable_virtual_hosts(0)->add_routes();
+  route3->mutable_match()->set_path("/grpc.testing.EchoTest3Service/Echo3");
+  route3->mutable_route()->set_cluster(kDefaultResourceName);
   auto* default_route = new_route_config.mutable_virtual_hosts(0)->add_routes();
   default_route->mutable_match()->set_prefix("");
   default_route->mutable_route()->set_cluster(kDefaultResourceName);