Add child refs support to grpclb

src/core/ext/filters/client_channel/client_channel_channelz.cc

@@ -85,12 +85,12 @@ void ClientChannelNode::PopulateChildRefs(grpc_json* json) {
     grpc_json* array_parent = grpc_json_create_child(
         nullptr, json, "channelRef", nullptr, GRPC_JSON_ARRAY, false);
     json_iterator = nullptr;
-    for (size_t i = 0; i < child_subchannels.size(); ++i) {
+    for (size_t i = 0; i < child_channels.size(); ++i) {
       json_iterator =
           grpc_json_create_child(json_iterator, array_parent, nullptr, nullptr,
                                  GRPC_JSON_OBJECT, false);
       grpc_json_add_number_string_child(json_iterator, nullptr, "channelId",
-                                        child_subchannels[i]);
+                                        child_channels[i]);
     }
   }
 }

src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc

@@ -135,9 +135,8 @@ class GrpcLb : public LoadBalancingPolicy {
   void HandOffPendingPicksLocked(LoadBalancingPolicy* new_policy) override;
   void PingOneLocked(grpc_closure* on_initiate, grpc_closure* on_ack) override;
   void ExitIdleLocked() override;
-  // TODO(ncteisen): implement this in a follow up PR
   void FillChildRefsForChannelz(ChildRefsList* child_subchannels,
-                                ChildRefsList* child_channels) override {}
+                                ChildRefsList* child_channels) override;
 
  private:
   /// Linked list of pending pick requests. It stores all information needed to
@@ -301,6 +300,9 @@ class GrpcLb : public LoadBalancingPolicy {
 
   // The channel for communicating with the LB server.
   grpc_channel* lb_channel_ = nullptr;
+  // Mutex to protect the channel to the LB server. This is used when
+  // processing a channelz request.
+  gpr_mu lb_channel_mu_;
   grpc_connectivity_state lb_channel_connectivity_;
   grpc_closure lb_channel_on_connectivity_changed_;
   // Are we already watching the LB channel's connectivity?
@@ -1040,6 +1042,7 @@ GrpcLb::GrpcLb(const grpc_lb_addresses* addresses,
               .set_max_backoff(GRPC_GRPCLB_RECONNECT_MAX_BACKOFF_SECONDS *
                                1000)) {
   // Initialization.
+  gpr_mu_init(&lb_channel_mu_);
   grpc_subchannel_index_ref();
   GRPC_CLOSURE_INIT(&lb_channel_on_connectivity_changed_,
                     &GrpcLb::OnBalancerChannelConnectivityChangedLocked, this,
@@ -1078,6 +1081,7 @@ GrpcLb::GrpcLb(const grpc_lb_addresses* addresses,
 GrpcLb::~GrpcLb() {
   GPR_ASSERT(pending_picks_ == nullptr);
   GPR_ASSERT(pending_pings_ == nullptr);
+  gpr_mu_destroy(&lb_channel_mu_);
   gpr_free((void*)server_name_);
   grpc_channel_args_destroy(args_);
   grpc_connectivity_state_destroy(&state_tracker_);
@@ -1107,8 +1111,10 @@ void GrpcLb::ShutdownLocked() {
   // OnBalancerChannelConnectivityChangedLocked(), and we need to be
   // alive when that callback is invoked.
   if (lb_channel_ != nullptr) {
+    gpr_mu_lock(&lb_channel_mu_);
     grpc_channel_destroy(lb_channel_);
     lb_channel_ = nullptr;
+    gpr_mu_unlock(&lb_channel_mu_);
   }
   grpc_connectivity_state_set(&state_tracker_, GRPC_CHANNEL_SHUTDOWN,
                               GRPC_ERROR_REF(error), "grpclb_shutdown");
@@ -1279,6 +1285,20 @@ void GrpcLb::PingOneLocked(grpc_closure* on_initiate, grpc_closure* on_ack) {
   }
 }
 
+void GrpcLb::FillChildRefsForChannelz(ChildRefsList* child_subchannels,
+                                      ChildRefsList* child_channels) {
+  // delegate to the RoundRobin to fill the children subchannels.
+  rr_policy_->FillChildRefsForChannelz(child_subchannels, child_channels);
+  mu_guard guard(&lb_channel_mu_);
+  if (lb_channel_ != nullptr) {
+    grpc_core::channelz::ChannelNode* channel_node =
+        grpc_channel_get_channelz_node(lb_channel_);
+    if (channel_node != nullptr) {
+      child_channels->push_back(channel_node->channel_uuid());
+    }
+  }
+}
+
 grpc_connectivity_state GrpcLb::CheckConnectivityLocked(
     grpc_error** connectivity_error) {
   return grpc_connectivity_state_get(&state_tracker_, connectivity_error);
@@ -1322,9 +1342,11 @@ void GrpcLb::ProcessChannelArgsLocked(const grpc_channel_args& args) {
   if (lb_channel_ == nullptr) {
     char* uri_str;
     gpr_asprintf(&uri_str, "fake:///%s", server_name_);
+    gpr_mu_lock(&lb_channel_mu_);
     lb_channel_ = grpc_client_channel_factory_create_channel(
         client_channel_factory(), uri_str,
         GRPC_CLIENT_CHANNEL_TYPE_LOAD_BALANCING, lb_channel_args);
+    gpr_mu_unlock(&lb_channel_mu_);
     GPR_ASSERT(lb_channel_ != nullptr);
     gpr_free(uri_str);
   }