Addressing code review comments.

src/core/ext/filters/client_channel/lb_policy/xds/xds_routing.cc

@@ -22,6 +22,7 @@
 
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_split.h"
+#include "absl/strings/string_view.h"
 
 #include <grpc/grpc.h>
 
@@ -52,24 +53,26 @@ class XdsRoutingLbConfig : public LoadBalancingPolicy::Config {
   struct ChildConfig {
     RefCountedPtr<LoadBalancingPolicy::Config> config;
   };
-
-  using Matcher = std::pair<std::string, std::string>;
-  using RouteVector = std::vector<std::pair<Matcher, std::string>>;
+  struct Matcher {
+    std::string service;
+    std::string method;
+  };
+  using RouteTable = std::vector<std::pair<Matcher, std::string>>;
   using ActionMap = std::map<std::string, ChildConfig>;
 
-  explicit XdsRoutingLbConfig(ActionMap action_map, RouteVector route_vector)
+  XdsRoutingLbConfig(ActionMap action_map, RouteTable route_table)
       : action_map_(std::move(action_map)),
-        route_vector_(std::move(route_vector)) {}
+        route_table_(std::move(route_table)) {}
 
   const char* name() const override { return kXdsRouting; }
 
   const ActionMap& action_map() const { return action_map_; }
 
-  const RouteVector& route_vector() const { return route_vector_; }
+  const RouteTable& route_table() const { return route_table_; }
 
  private:
   ActionMap action_map_;
-  RouteVector route_vector_;
+  RouteTable route_table_;
 };
 
 // xds_routing LB policy.
@@ -87,39 +90,37 @@ class XdsRoutingLb : public LoadBalancingPolicy {
   // A simple wrapper for ref-counting a picker from the child policy.
   class ChildPickerWrapper : public RefCounted<ChildPickerWrapper> {
    public:
-    explicit ChildPickerWrapper(const std::string& name,
+    ChildPickerWrapper(std::string name,
                        std::unique_ptr<SubchannelPicker> picker)
-        : name_(name), picker_(std::move(picker)) {}
+        : name_(std::move(name)), picker_(std::move(picker)) {}
     PickResult Pick(PickArgs args) { return picker_->Pick(std::move(args)); }
 
-    std::string name() { return name_; }
+    const std::string& name() { return name_; }
 
    private:
     std::string name_;
     std::unique_ptr<SubchannelPicker> picker_;
   };
 
-  // Picks a child using stateless WRR and then delegates to that
+  // Picks a child using prefix or path matching and then delegates to that
   // child's picker.
-  class XdsRoutingPicker : public SubchannelPicker {
+  class RoutePicker : public SubchannelPicker {
    public:
-    // Maintains a xds_routing list of pickers from each child that is in
-    // ready state. The first element in the pair represents the end of a
-    // range proportional to the child's weight. The start of the range
-    // is the previous value in the vector and is 0 for the first element.
-    using PickerList = InlinedVector<RefCountedPtr<ChildPickerWrapper>, 1>;
+    struct Route {
+      XdsRoutingLbConfig::Matcher matcher;
+      RefCountedPtr<ChildPickerWrapper> picker;
+    };
 
-    using PickerMap = std::map<std::string, RefCountedPtr<ChildPickerWrapper>>;
+    // Maintains an ordered xds route table as provided by RDS response.
+    using RouteTable = std::vector<Route>;
 
-    XdsRoutingPicker(RefCountedPtr<XdsRoutingLb> parent, PickerMap pickers)
-        : parent_(std::move(parent)), pickers_(std::move(pickers)) {}
-    ~XdsRoutingPicker() { parent_.reset(DEBUG_LOCATION, "XdsRoutingPicker"); }
+    RoutePicker(RouteTable route_table)
+        : route_table_(std::move(route_table)) {}
 
     PickResult Pick(PickArgs args) override;
 
    private:
-    RefCountedPtr<XdsRoutingLb> parent_;
-    PickerMap pickers_;
+    RouteTable route_table_;
   };
 
   // Each XdsRoutingChild holds a ref to its parent XdsRoutingLb.
@@ -145,8 +146,6 @@ class XdsRoutingLb : public LoadBalancingPolicy {
       return picker_wrapper_;
     }
 
-    std::string name() const { return name_; }
-
    private:
     class Helper : public ChannelControlHelper {
      public:
@@ -211,35 +210,29 @@ class XdsRoutingLb : public LoadBalancingPolicy {
 };
 
 //
-// XdsRoutingLb::XdsRoutingPicker
+// XdsRoutingLb::RoutePicker
 //
 
-XdsRoutingLb::PickResult XdsRoutingLb::XdsRoutingPicker::Pick(PickArgs args) {
-  std::string path;
+XdsRoutingLb::PickResult XdsRoutingLb::RoutePicker::Pick(PickArgs args) {
+  absl::string_view path;
   for (const auto& p : *(args.initial_metadata)) {
-    if (memcmp(p.first.data(), ":path", static_cast<int>(p.first.size())) ==
-        0) {
-      path = std::string(p.second.data(), static_cast<int>(p.second.size()));
+    if (p.first == ":path") {
+      path = p.second;
       break;
     }
   }
-  std::vector<std::string> v = absl::StrSplit(path, '/');
-  GPR_DEBUG_ASSERT(v.size() == 3);
-  std::string service = v[1];
-  std::string method = v[2];
-  for (int i = 0; i < parent_->config_->route_vector().size(); ++i) {
-    if (service == parent_->config_->route_vector()[i].first.first &&
-        ("" == parent_->config_->route_vector()[i].first.second ||
-         method == parent_->config_->route_vector()[i].first.second)) {
-      auto picker = pickers_.find(parent_->config_->route_vector()[i].second);
-      if (picker != pickers_.end()) {
-        gpr_log(GPR_INFO, "XdsRouting Picked: %s for path %s",
-                picker->first.c_str(), path.c_str());
-        return picker->second.get()->Pick(args);
+  std::vector<absl::string_view> v = absl::StrSplit(path.substr(1), '/');
+  for (int i = 0; i < route_table_.size(); ++i) {
+    if (v[0] == route_table_[i].matcher.service &&
+        ("" == route_table_[i].matcher.method ||
+         v[1] == route_table_[i].matcher.method)) {
+      auto picker = route_table_[i].picker;
+      if (picker != nullptr) {
+        return picker.get()->Pick(args);
       }
     }
   }
-  return pickers_.begin()->second.get()->Pick(args);
+  return route_table_[route_table_.size() - 1].picker.get()->Pick(args);
 }
 
 //
@@ -313,11 +306,7 @@ void XdsRoutingLb::UpdateLocked(UpdateArgs args) {
 }
 
 void XdsRoutingLb::UpdateStateLocked() {
-  // Construct a new picker which maintains a map of all child pickers
-  // that are ready. Each child is represented by a portion of the range
-  // proportional to its weight, such that the total range is the sum of the
-  // weights of all children.
-  XdsRoutingPicker::PickerMap picker_map;
+  std::map<std::string, RefCountedPtr<ChildPickerWrapper>> picker_map;
   // Also count the number of children in each state, to determine the
   // overall state.
   size_t num_connecting = 0;
@@ -367,10 +356,19 @@ void XdsRoutingLb::UpdateStateLocked() {
             ConnectivityStateName(connectivity_state));
   }
   std::unique_ptr<SubchannelPicker> picker;
+  RoutePicker::RouteTable route_table;
   switch (connectivity_state) {
     case GRPC_CHANNEL_READY:
-      picker = absl::make_unique<XdsRoutingPicker>(
-          Ref(DEBUG_LOCATION, "XdsRoutingPicker"), std::move(picker_map));
+      for (int i = 0; i < config_->route_table().size(); ++i) {
+        RoutePicker::Route route;
+        route.matcher = config_->route_table()[i].first;
+        auto child_picker = picker_map.find(config_->route_table()[i].second);
+        if (child_picker != picker_map.end()) {
+          route.picker = child_picker->second;
+        }
+        route_table.push_back(std::move(route));
+      }
+      picker = absl::make_unique<RoutePicker>(std::move(route_table));
       break;
     case GRPC_CHANNEL_CONNECTING:
     case GRPC_CHANNEL_IDLE:
@@ -460,6 +458,7 @@ void XdsRoutingLb::XdsRoutingChild::UpdateLocked(
   // Update child weight.
   // Reactivate if needed.
   if (delayed_removal_timer_callback_pending_) {
+    delayed_removal_timer_callback_pending_ = false;
     grpc_timer_cancel(&delayed_removal_timer_);
   }
   // Create child policy if needed.
@@ -530,7 +529,6 @@ void XdsRoutingLb::XdsRoutingChild::OnDelayedRemovalTimerLocked(
 RefCountedPtr<SubchannelInterface>
 XdsRoutingLb::XdsRoutingChild::Helper::CreateSubchannel(
     const grpc_channel_args& args) {
-  gpr_log(GPR_INFO, "XdsRoutingChild::Helper::CreateSubchannel");
   if (xds_routing_child_->xds_routing_policy_->shutting_down_) return nullptr;
   return xds_routing_child_->xds_routing_policy_->channel_control_helper()
       ->CreateSubchannel(args);
@@ -538,12 +536,15 @@ XdsRoutingLb::XdsRoutingChild::Helper::CreateSubchannel(
 
 void XdsRoutingLb::XdsRoutingChild::Helper::UpdateState(
     grpc_connectivity_state state, std::unique_ptr<SubchannelPicker> picker) {
-  gpr_log(GPR_INFO, "XdsRoutingChild::Helper::UpdateState %s",
-          xds_routing_child_->name().c_str());
+  if (GRPC_TRACE_FLAG_ENABLED(grpc_xds_routing_lb_trace)) {
+    gpr_log(GPR_INFO,
+            "XdsRoutingChild::Helper::UpdateState child %s, state %d, piker %p",
+            xds_routing_child_->name_.c_str(), state, picker.get());
+  }
   if (xds_routing_child_->xds_routing_policy_->shutting_down_) return;
   // Cache the picker in the XdsRoutingChild.
   xds_routing_child_->picker_wrapper_ = MakeRefCounted<ChildPickerWrapper>(
-      xds_routing_child_->name(), std::move(picker));
+      xds_routing_child_->name_, std::move(picker));
   // Decide what state to report for aggregation purposes.
   // If we haven't seen a failure since the last time we were in state
   // READY, then we report the state change as-is.  However, once we do see
@@ -607,87 +608,67 @@ class XdsRoutingLbFactory : public LoadBalancingPolicyFactory {
     if (it == json.object_value().end()) {
       error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
           "field:actions error:required field not present"));
-    } else if (it->second.type() != Json::Type::ARRAY) {
+    } else if (it->second.type() != Json::Type::OBJECT) {
       error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-          "field:actions error:type should be array"));
+          "field:actions error:type should be object"));
     } else {
-      for (const auto& p : it->second.array_value()) {
-        auto it_cds = p.object_value().find("cds");
-        auto it_weighted_target = p.object_value().find("weighted_target");
-        if (it_cds == p.object_value().end() &&
-            it_weighted_target == p.object_value().end()) {
-          error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-              "field:actions error: each action needs to be either cds or "
-              "weighted target"));
-        }
-        auto it_name =
-            (it_cds == p.object_value().end() ? it_weighted_target : it_cds);
-        auto it_child_policy = p.object_value().find("child_policy");
-        if (it_child_policy == p.object_value().end()) {
-          error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-              "field:actions error: each action needs child policies"));
-        }
+      for (const auto& p : it->second.object_value()) {
         XdsRoutingLbConfig::ChildConfig child_config;
         std::vector<grpc_error*> child_errors =
-            ParseChildConfig(it_child_policy->second, &child_config);
+            ParseChildConfig(p.second, &child_config);
         if (!child_errors.empty()) {
           // Can't use GRPC_ERROR_CREATE_FROM_VECTOR() here, because the error
           // string is not static in this case.
           grpc_error* error = GRPC_ERROR_CREATE_FROM_COPIED_STRING(
-              absl::StrCat("field:actions name:",
-                           it_name->second.string_value())
-                  .c_str());
+              absl::StrCat("field:actions name:", p.first).c_str());
           for (grpc_error* child_error : child_errors) {
             error = grpc_error_add_child(error, child_error);
           }
           error_list.push_back(error);
         } else {
-          action_map[it_name->second.string_value()] = std::move(child_config);
+          action_map[p.first] = std::move(child_config);
         }
       }
     }
-    XdsRoutingLbConfig::RouteVector route_vector;
-    auto route_iter = json.object_value().find("routes");
-    if (route_iter == json.object_value().end()) {
-      gpr_log(GPR_INFO, "No routes specified");
-    } else if (route_iter->second.type() != Json::Type::ARRAY) {
-      error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-          "field:routes error:type should be array"));
-    } else {
-      for (const auto& p : route_iter->second.array_value()) {
-        auto method_name = p.object_value().find("methodName");
-        if (method_name == p.object_value().end()) {
+    XdsRoutingLbConfig::RouteTable route_table;
+    it = json.object_value().find("routes");
+    if (it == json.object_value().end()) {
       error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-              "field:routes error:methodName is required"));
-        } else {
-          auto action_name = p.object_value().find("action");
-          if (action_name == p.object_value().end()) {
+          "field:routes error:required field not present"));
+    } else if (it->second.type() != Json::Type::ARRAY) {
       error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-                "field:routes error:action is required"));
+          "field:routes error:type should be array"));
     } else {
+      for (const auto& route : it->second.array_value()) {
+        // Parse methodName.
         XdsRoutingLbConfig::Matcher matcher;
-            auto service = method_name->second.object_value().find("service");
-            auto method = method_name->second.object_value().find("method");
-            if (service == method_name->second.object_value().end() &&
-                method != method_name->second.object_value().end()) {
-              error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-                  "field:methodName error: service is empty when method is "
-                  "not"));
-            }
-            if (service != method_name->second.object_value().end()) {
-              matcher.first = service->second.string_value();
-            } else {
-              matcher.first = "";
+        std::vector<grpc_error*> route_errors =
+            ParseRouteConfig(route.object_value(), &matcher);
+        if (!route_errors.empty()) {
+          // Can't use GRPC_ERROR_CREATE_FROM_VECTOR() here, because the error
+          // string is not static in this case.
+          grpc_error* error =
+              GRPC_ERROR_CREATE_FROM_COPIED_STRING("field:routes error");
+          for (grpc_error* route_error : route_errors) {
+            error = grpc_error_add_child(error, route_error);
           }
-            if (method != method_name->second.object_value().end()) {
-              matcher.second = method->second.string_value();
-            } else {
-              matcher.first = "";
+          error_list.push_back(error);
         }
-            route_vector.emplace_back(matcher,
-                                      action_name->second.string_value());
+        // Parse action.
+        std::string cluster_name;
+        std::vector<grpc_error*> action_errors =
+            ParseActionConfig(route.object_value(), &cluster_name);
+        if (!action_errors.empty()) {
+          // Can't use GRPC_ERROR_CREATE_FROM_VECTOR() here, because the error
+          // string is not static in this case.
+          grpc_error* error =
+              GRPC_ERROR_CREATE_FROM_COPIED_STRING("field:actions error:");
+          for (grpc_error* action_error : action_errors) {
+            error = grpc_error_add_child(error, action_error);
           }
+          error_list.push_back(error);
         }
+        route_table.emplace_back(std::move(matcher), std::move(cluster_name));
       }
     }
     if (!error_list.empty()) {
@@ -696,22 +677,24 @@ class XdsRoutingLbFactory : public LoadBalancingPolicyFactory {
       return nullptr;
     }
     return MakeRefCounted<XdsRoutingLbConfig>(std::move(action_map),
-                                              std::move(route_vector));
+                                              std::move(route_table));
   }
 
  private:
   static std::vector<grpc_error*> ParseChildConfig(
       const Json& json, XdsRoutingLbConfig::ChildConfig* child_config) {
     std::vector<grpc_error*> error_list;
-    if (json.type() != Json::Type::ARRAY) {
+    if (json.type() != Json::Type::OBJECT) {
       error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-          "value should be of type array"));
+          "value should be of type object"));
       return error_list;
     }
+    auto it = json.object_value().find("child_policy");
+    if (it != json.object_value().end()) {
       grpc_error* parse_error = GRPC_ERROR_NONE;
       child_config->config =
-        LoadBalancingPolicyRegistry::ParseLoadBalancingConfig(
-            json.array_value(), &parse_error);
+          LoadBalancingPolicyRegistry::ParseLoadBalancingConfig(it->second,
+                                                                &parse_error);
       if (child_config->config == nullptr) {
         GPR_DEBUG_ASSERT(parse_error != GRPC_ERROR_NONE);
         std::vector<grpc_error*> child_errors;
@@ -719,6 +702,68 @@ class XdsRoutingLbFactory : public LoadBalancingPolicyFactory {
         error_list.push_back(
             GRPC_ERROR_CREATE_FROM_VECTOR("field:childPolicy", &child_errors));
       }
+    } else {
+      error_list.push_back(
+          GRPC_ERROR_CREATE_FROM_STATIC_STRING("did not find childPolicy"));
+    }
+    return error_list;
+  }
+
+  static std::vector<grpc_error*> ParseRouteConfig(
+      const Json& json, XdsRoutingLbConfig::Matcher* route_config) {
+    std::vector<grpc_error*> error_list;
+    if (json.type() != Json::Type::OBJECT) {
+      error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+          "value should be of type object"));
+      return error_list;
+    }
+    auto method_name = json.object_value().find("methodName");
+    if (method_name == json.object_value().end()) {
+      error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+          "field:routes error:methodName is required"));
+    } else if (method_name->second.type() != Json::Type::OBJECT) {
+      error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+          "field:routes error:methodName error: type should be object"));
+    } else {
+      auto service = method_name->second.object_value().find("service");
+      auto method = method_name->second.object_value().find("method");
+      if (service != method_name->second.object_value().end()) {
+        route_config->service = service->second.string_value();
+      } else {
+        route_config->service = "";
+      }
+      if (method != method_name->second.object_value().end()) {
+        route_config->method = method->second.string_value();
+      } else {
+        route_config->method = "";
+      }
+      if ((route_config->service == "") && (route_config->method != "")) {
+        error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+            "field:methodName error: service is empty when method is "
+            "not"));
+      }
+    }
+    return error_list;
+  }
+
+  static std::vector<grpc_error*> ParseActionConfig(const Json& json,
+                                                    std::string* cluster_name) {
+    std::vector<grpc_error*> error_list;
+    if (json.type() != Json::Type::OBJECT) {
+      error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+          "value should be of type object"));
+      return error_list;
+    }
+    auto action_name = json.object_value().find("action");
+    if (action_name == json.object_value().end()) {
+      error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+          "field:routes error:action is required"));
+    } else if (action_name->second.type() != Json::Type::STRING) {
+      error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+          "field:methodName error:type should be string"));
+    } else {
+      *cluster_name = action_name->second.string_value();
+    }
     return error_list;
   }
 };

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

@@ -1012,7 +1012,6 @@ grpc_error* RouteConfigParse(
     return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
         "No route found in the virtual host.");
   }
-
   for (size_t i = 0; i < size; ++i) {
     const envoy_api_v2_route_Route* route = routes[i];
     const envoy_api_v2_route_RouteMatch* match =
@@ -1020,28 +1019,28 @@ grpc_error* RouteConfigParse(
     XdsApi::RdsRoute rds_route;
     const upb_strview prefix = envoy_api_v2_route_RouteMatch_prefix(match);
     const upb_strview path = envoy_api_v2_route_RouteMatch_path(match);
-    if (!upb_strview_eql(prefix, upb_strview_makez(""))) {
-      std::string prefix_string = std::string(prefix.data, prefix.size);
-      std::vector<std::string> v = absl::StrSplit(prefix_string, '/');
-      if (v.size() != 2) {
+    if (prefix.size > 0) {
+      std::vector<absl::string_view> v = absl::StrSplit(
+          absl::string_view(prefix.data, prefix.size).substr(1), '/');
+      if (v.size() != 1) {
         return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
             "Prefix not in the required format of /service/");
       }
-      rds_route.service = v[1];
-      if (!upb_strview_eql(path, upb_strview_makez(""))) {
+      rds_route.service = std::string(v[0].data(), v[0].size());
+      if (path.size > 0) {
         return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
             "Prefix is not empty string, path cannot also be non-empty.");
       }
-    } else if (!upb_strview_eql(path, upb_strview_makez(""))) {
-      std::string path_string = std::string(path.data, path.size);
-      std::vector<std::string> v = absl::StrSplit(path_string, '/');
-      if (v.size() != 3) {
+    } else if (path.size > 0) {
+      std::vector<absl::string_view> v = absl::StrSplit(
+          absl::string_view(path.data, path.size).substr(1), '/');
+      if (v.size() != 2) {
         return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
             "Path not in the required format of /service/method");
       }
-      rds_route.service = v[1];
-      rds_route.method = v[2];
-      if (!upb_strview_eql(prefix, upb_strview_makez(""))) {
+      rds_route.service = std::string(v[0].data(), v[0].size());
+      rds_route.method = std::string(v[1].data(), v[1].size());
+      if (prefix.size > 0) {
         return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
             "Path is not empty string, prefix cannot also be non-empty.");
       }
@@ -1059,13 +1058,12 @@ grpc_error* RouteConfigParse(
     }
     const upb_strview action =
         envoy_api_v2_route_RouteAction_cluster(route_action);
-    rds_route.action_name = std::string(action.data, action.size);
+    rds_route.cluster_name = std::string(action.data, action.size);
     rds_update->routes.emplace_back(std::move(rds_route));
-    gpr_log(GPR_INFO, "RouteConfigParse a route %s %s %s %s",
+    gpr_log(GPR_INFO, "RouteConfigParse a route %s %s %s",
             rds_update->routes[i].service.c_str(),
             rds_update->routes[i].method.c_str(),
-            rds_update->routes[i].action_type.c_str(),
-            rds_update->routes[i].action_name.c_str());
+            rds_update->routes[i].cluster_name.c_str());
   }
   return GRPC_ERROR_NONE;
 }

src/core/ext/filters/client_channel/xds/xds_api.h

@@ -46,8 +46,7 @@ class XdsApi {
   struct RdsRoute {
     std::string service;
     std::string method;
-    std::string action_type;
-    std::string action_name;
+    std::string cluster_name;
   };
 
   struct RdsUpdate {

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

@@ -22,6 +22,7 @@
 #include <limits.h>
 #include <string.h>
 
+#include "absl/strings/str_format.h"
 #include "absl/strings/str_join.h"
 
 #include <grpc/byte_buffer_reader.h>
@@ -70,6 +71,35 @@ namespace grpc_core {
 
 TraceFlag grpc_xds_client_trace(false, "xds_client");
 
+namespace {
+
+std::string CreateServiceConfigActionCluster(const std::string& cluster_name) {
+  std::string json = absl::StrFormat(
+      "      \"cds:%s\":{\n"
+      "        \"child_policy\":[\n"
+      "          { \"cds_experimental\":{\n"
+      "            \"cluster\": \"%s\"\n"
+      "          } }\n"
+      "        ]\n"
+      "       }",
+      cluster_name.c_str(), cluster_name.c_str());
+  return json;
+}
+
+std::string CreateServiceConfigRoute(const std::string& cluster_name,
+                                     const std::string& service,
+                                     const std::string& method) {
+  std::string json = absl::StrFormat(
+      "      { \"methodName\":\n"
+      "      { \"service\": \"%s\",\n"
+      "        \"method\": \"%s\"},\n"
+      "      \"action\": \"cds:%s\"\n"
+      "      }",
+      service.c_str(), method.c_str(), cluster_name.c_str());
+  return json;
+}
+
+}  // namespace
 //
 // Internal class declarations
 //
@@ -888,35 +918,23 @@ void XdsClient::ChannelState::AdsCallState::AcceptLdsUpdate(
             "LDS update does not include requested resource"));
     return;
   }
-  const std::string& cluster_name =
-      lds_update->rds_update.has_value()
-          ? lds_update->rds_update.value().routes[0].action_name
-          : "";
   if (GRPC_TRACE_FLAG_ENABLED(grpc_xds_client_trace)) {
     gpr_log(GPR_INFO,
-            "[xds_client %p] LDS update received: route_config_name=%s, "
-            "cluster_name=%s (empty if RDS is needed to obtain it)",
-            xds_client(), lds_update->route_config_name.c_str(),
-            cluster_name.c_str());
-    for (auto route : lds_update->rds_update.value().routes) {
-      gpr_log(GPR_INFO, "Create service config using %s %s %s %s",
+            "[xds_client %p] LDS update received: route_config_name=%s",
+            xds_client(), lds_update->route_config_name.c_str());
+    if (lds_update->rds_update.has_value()) {
+      for (const auto& route : lds_update->rds_update.value().routes) {
+        gpr_log(GPR_INFO,
+                "Create service config using route: { service=\"%s\", "
+                "method=\"%s\" }, cluster=\"%s\" }",
                 route.service.c_str(), route.method.c_str(),
-              route.action_type.c_str(), route.action_name.c_str());
+                route.cluster_name.c_str());
+      }
     }
   }
   auto& lds_state = state_map_[XdsApi::kLdsTypeUrl];
   auto& state = lds_state.subscribed_resources[xds_client()->server_name_];
   if (state != nullptr) state->Finish();
-  // Ignore identical update.
-  if (xds_client()->route_config_name_ == lds_update->route_config_name &&
-      xds_client()->cluster_name_ == cluster_name) {
-    if (GRPC_TRACE_FLAG_ENABLED(grpc_xds_client_trace)) {
-      gpr_log(GPR_INFO,
-              "[xds_client %p] LDS update identical to current, ignoring.",
-              xds_client());
-    }
-    return;
-  }
   if (!xds_client()->route_config_name_.empty()) {
     Unsubscribe(
         XdsApi::kRdsTypeUrl, xds_client()->route_config_name_,
@@ -924,10 +942,8 @@ void XdsClient::ChannelState::AdsCallState::AcceptLdsUpdate(
   }
   xds_client()->route_config_name_ = lds_update->route_config_name;
   if (lds_update->rds_update.has_value()) {
-    // If cluster_name was found inlined in LDS response, notify the watcher
-    // immediately.
-    xds_client()->cluster_name_ =
-        lds_update->rds_update.value().routes[0].action_name;
+    // If the RouteConfiguration was found inlined in LDS response, notify the
+    // watcher immediately.
     RefCountedPtr<ServiceConfig> service_config;
     grpc_error* error = xds_client()->CreateServiceConfig(
         lds_update->rds_update.value(), &service_config);
@@ -954,24 +970,10 @@ void XdsClient::ChannelState::AdsCallState::AcceptRdsUpdate(
             "RDS update does not include requested resource"));
     return;
   }
-  if (GRPC_TRACE_FLAG_ENABLED(grpc_xds_client_trace)) {
-    gpr_log(GPR_INFO, "[xds_client %p] RDS update received: cluster_name=%s",
-            xds_client(), rds_update->routes[0].action_name.c_str());
-  }
   auto& rds_state = state_map_[XdsApi::kRdsTypeUrl];
   auto& state =
       rds_state.subscribed_resources[xds_client()->route_config_name_];
   if (state != nullptr) state->Finish();
-  // Ignore identical update.
-  if (xds_client()->cluster_name_ == rds_update->routes[0].action_name) {
-    if (GRPC_TRACE_FLAG_ENABLED(grpc_xds_client_trace)) {
-      gpr_log(GPR_INFO,
-              "[xds_client %p] RDS update identical to current, ignoring.",
-              xds_client());
-    }
-    return;
-  }
-  xds_client()->cluster_name_ = rds_update->routes[0].action_name;
   // Notify the watcher.
   RefCountedPtr<ServiceConfig> service_config;
   grpc_error* error =
@@ -2043,85 +2045,46 @@ void XdsClient::ResetBackoff() {
   }
 }
 
-char* XdsClient::CreateServiceConfigActionCluster(
-    const std::string& cluster_name, const bool without_comma) const {
-  const char* last_line = without_comma ? "}" : "},";
-  char* json;
-  gpr_asprintf(&json,
-               "      { \"cds\": \"%s\",\n"
-               "        \"child_policy\":[\n"
-               "          { \"cds_experimental\":{\n"
-               "            \"cluster\": \"%s\"\n"
-               "          } }\n"
-               "        ]\n"
-               "      %s\n",
-               cluster_name.c_str(), cluster_name.c_str(), last_line);
-  return json;
-}
-
-char* XdsClient::CreateServiceConfigRoute(const std::string& cluster_name,
-                                          const std::string& service,
-                                          const std::string& method,
-                                          const bool without_comma) const {
-  const char* last_line = without_comma ? "}" : "},";
-  char* json;
-  gpr_asprintf(&json,
-               "      { \"methodName\":\n"
-               "      { \"service\": \"%s\",\n"
-               "        \"method\": \"%s\"},\n"
-               "      \"action\": \"%s\"\n"
-               "      %s\n",
-               service.c_str(), method.c_str(), cluster_name.c_str(),
-               last_line);
-  return json;
-}
-
 grpc_error* XdsClient::CreateServiceConfig(
     const XdsApi::RdsUpdate& rds_update,
     RefCountedPtr<ServiceConfig>* service_config) const {
-  gpr_strvec v;
-  gpr_strvec_init(&v);
-  char* json_start;
-  gpr_asprintf(&json_start,
-               "{\n"
+  std::vector<std::string> v;
+  std::string json_start =
+      ("{\n"
        "  \"loadBalancingConfig\":[\n"
        "    { \"xds_routing_experimental\":{\n"
-               "      \"actions\":[\n");
-  gpr_strvec_add(&v, json_start);
+       "      \"actions\":{\n");
+  v.push_back(std::move(json_start));
+  std::vector<std::string> actions_vector;
   for (size_t i = 0; i < rds_update.routes.size(); ++i) {
     auto route = rds_update.routes[i];
-    // TODO: (donnadionne) CreateServiceConfigActionWeightedTarget
-    char* action = CreateServiceConfigActionCluster(
-        route.action_name.c_str(), i == (rds_update.routes.size() - 1));
-    gpr_strvec_add(&v, action);
-  }
-  char* json_transition;
-  gpr_asprintf(&json_transition,
-               "    ],\n"
+    actions_vector.push_back(
+        CreateServiceConfigActionCluster(route.cluster_name.c_str()));
+  }
+  v.push_back(absl::StrJoin(actions_vector, ","));
+  std::string json_transition =
+      ("    },\n"
        "      \"routes\":[\n");
-  gpr_strvec_add(&v, json_transition);
+  v.push_back(std::move(json_transition));
+  std::vector<std::string> routes_vector;
   for (size_t i = 0; i < rds_update.routes.size(); ++i) {
     auto route_info = rds_update.routes[i];
-    char* route = CreateServiceConfigRoute(
-        route_info.action_name.c_str(), route_info.service.c_str(),
-        route_info.method.c_str(), i == (rds_update.routes.size() - 1));
-    gpr_strvec_add(&v, route);
+    routes_vector.push_back(CreateServiceConfigRoute(
+        route_info.cluster_name.c_str(), route_info.service.c_str(),
+        route_info.method.c_str()));
   }
-  char* json_end;
-  gpr_asprintf(&json_end,
-               "    ]\n"
+  v.push_back(absl::StrJoin(routes_vector, ","));
+  std::string json_end =
+      ("    ]\n"
        "    } }\n"
        "  ]\n"
        "}");
-  gpr_strvec_add(&v, json_end);
-  size_t len;
-  char* json = gpr_strvec_flatten(&v, &len);
-  gpr_strvec_destroy(&v);
+  v.push_back(std::move(json_end));
+  std::string json = absl::StrJoin(v, "");
   grpc_error* error = GRPC_ERROR_NONE;
-  *service_config = ServiceConfig::Create(json, &error);
+  *service_config = ServiceConfig::Create(json.c_str(), &error);
   gpr_log(GPR_INFO, "Built service config: \"%s\"",
           service_config->get()->json_string().c_str());
-  gpr_free(json);
   return error;
 }
 

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

@@ -218,13 +218,6 @@ class XdsClient : public InternallyRefCounted<XdsClient> {
   // Sends an error notification to all watchers.
   void NotifyOnError(grpc_error* error);
 
-  char* CreateServiceConfigActionCluster(
-      const std::string& cluster_name, const bool without_comma = false) const;
-  char* CreateServiceConfigRoute(const std::string& prefix,
-                                 const std::string& service,
-                                 const std::string& method,
-                                 const bool without_comma = false) const;
-
   grpc_error* CreateServiceConfig(
       const XdsApi::RdsUpdate& rds_update,
       RefCountedPtr<ServiceConfig>* service_config) const;
@@ -254,7 +247,6 @@ class XdsClient : public InternallyRefCounted<XdsClient> {
   OrphanablePtr<ChannelState> chand_;
 
   std::string route_config_name_;
-  std::string cluster_name_;
   // One entry for each watched CDS resource.
   std::map<std::string /*cluster_name*/, ClusterState> cluster_map_;
   // One entry for each watched EDS resource.

src/core/plugin_registry/grpc_unsecure_plugin_registry.cc

@@ -46,6 +46,8 @@ void grpc_lb_policy_cds_init(void);
 void grpc_lb_policy_cds_shutdown(void);
 void grpc_lb_policy_xds_init(void);
 void grpc_lb_policy_xds_shutdown(void);
+void grpc_lb_policy_xds_routing_init(void);
+void grpc_lb_policy_xds_routing_shutdown(void);
 void grpc_lb_policy_pick_first_init(void);
 void grpc_lb_policy_pick_first_shutdown(void);
 void grpc_lb_policy_round_robin_init(void);
@@ -88,6 +90,8 @@ void grpc_register_built_in_plugins(void) {
                        grpc_lb_policy_cds_shutdown);
   grpc_register_plugin(grpc_lb_policy_xds_init,
                        grpc_lb_policy_xds_shutdown);
+  grpc_register_plugin(grpc_lb_policy_xds_routing_init,
+                       grpc_lb_policy_xds_routing_shutdown);
   grpc_register_plugin(grpc_lb_policy_pick_first_init,
                        grpc_lb_policy_pick_first_shutdown);
   grpc_register_plugin(grpc_lb_policy_round_robin_init,

test/cpp/end2end/xds_end2end_test.cc

@@ -1946,15 +1946,9 @@ TEST_P(LdsTest, XdsRoutingPathMatching) {
   // Change RDS resource to point to new cluster.
   RouteConfiguration new_route_config =
       balancers_[0]->ads_service()->default_route_config();
-  new_route_config.mutable_virtual_hosts(0)
-      ->mutable_routes(0)
-      ->mutable_match()
-      ->set_path("/grpc.testing.EchoTestService/Echo");
-  //->set_prefix("/dgrpc.testing.EchoTestService");
-  new_route_config.mutable_virtual_hosts(0)
-      ->mutable_routes(0)
-      ->mutable_route()
-      ->set_cluster(kNewClusterName);
+  auto* route = new_route_config.mutable_virtual_hosts(0)->mutable_routes(0);
+  route->mutable_match()->set_path("/grpc.testing.EchoTestService/Echo");
+  route->mutable_route()->set_cluster(kNewClusterName);
   Listener listener =
       balancers_[0]->ads_service()->BuildListener(new_route_config);
   balancers_[0]->ads_service()->SetLdsResource(listener, kDefaultResourceName);
@@ -1989,14 +1983,9 @@ TEST_P(LdsTest, XdsRoutingPrefixMatching) {
   // Change RDS resource to point to new cluster.
   RouteConfiguration new_route_config =
       balancers_[0]->ads_service()->default_route_config();
-  new_route_config.mutable_virtual_hosts(0)
-      ->mutable_routes(0)
-      ->mutable_match()
-      ->set_prefix("/grpc.testing.EchoTestService");
-  new_route_config.mutable_virtual_hosts(0)
-      ->mutable_routes(0)
-      ->mutable_route()
-      ->set_cluster(kNewClusterName);
+  auto* route = new_route_config.mutable_virtual_hosts(0)->mutable_routes(0);
+  route->mutable_match()->set_prefix("/grpc.testing.EchoTestService");
+  route->mutable_route()->set_cluster(kNewClusterName);
   Listener listener =
       balancers_[0]->ads_service()->BuildListener(new_route_config);
   balancers_[0]->ads_service()->SetLdsResource(listener, kDefaultResourceName);