1 files changed, 32 insertions, 6 deletions

diff --git a/src/core/ext/filters/client_channel/subchannel.cc b/src/core/ext/filters/client_channel/subchannel.cc
index 0e40f42e18..57d0b3759f 100644
--- a/src/core/ext/filters/client_channel/subchannel.cc
+++ b/src/core/ext/filters/client_channel/subchannel.cc
@@ -183,7 +183,13 @@ static void connection_destroy(void* arg, grpc_error* error) {
 
 static void subchannel_destroy(void* arg, grpc_error* error) {
   grpc_subchannel* c = static_cast<grpc_subchannel*>(arg);
-  c->channelz_subchannel.reset();
+  if (c->channelz_subchannel != nullptr) {
+    c->channelz_subchannel->AddTraceEvent(
+        grpc_core::channelz::ChannelTrace::Severity::Info,
+        grpc_slice_from_static_string("Subchannel destroyed"));
+    c->channelz_subchannel->MarkSubchannelDestroyed();
+    c->channelz_subchannel.reset();
+  }
   gpr_free((void*)c->filters);
   grpc_channel_args_destroy(c->args);
   grpc_connectivity_state_destroy(&c->state_tracker);
@@ -383,9 +389,18 @@ grpc_subchannel* grpc_subchannel_create(grpc_connector* connector,
   const grpc_arg* arg =
       grpc_channel_args_find(c->args, GRPC_ARG_ENABLE_CHANNELZ);
   bool channelz_enabled = grpc_channel_arg_get_bool(arg, false);
+  arg = grpc_channel_args_find(c->args,
+                               GRPC_ARG_MAX_CHANNEL_TRACE_EVENTS_PER_NODE);
+  const grpc_integer_options options = {0, 0, INT_MAX};
+  size_t channel_tracer_max_nodes =
+      (size_t)grpc_channel_arg_get_integer(arg, options);
   if (channelz_enabled) {
     c->channelz_subchannel =
-        grpc_core::MakeRefCounted<grpc_core::channelz::SubchannelNode>();
+        grpc_core::MakeRefCounted<grpc_core::channelz::SubchannelNode>(
+            c, channel_tracer_max_nodes);
+    c->channelz_subchannel->AddTraceEvent(
+        grpc_core::channelz::ChannelTrace::Severity::Info,
+        grpc_slice_from_static_string("Subchannel created"));
   }
 
   return grpc_subchannel_index_register(key, c);
@@ -625,8 +640,8 @@ static bool publish_transport_locked(grpc_subchannel* c) {
   }
 
   /* publish */
-  c->connected_subchannel.reset(
-      grpc_core::New<grpc_core::ConnectedSubchannel>(stk));
+  c->connected_subchannel.reset(grpc_core::New<grpc_core::ConnectedSubchannel>(
+      stk, c->channelz_subchannel.get()));
   gpr_log(GPR_INFO, "New connected subchannel at %p for subchannel %p",
           c->connected_subchannel.get(), c);
 
@@ -770,6 +785,14 @@ void grpc_get_subchannel_address_arg(const grpc_channel_args* args,
   }
 }
 
+const char* grpc_subchannel_get_target(grpc_subchannel* subchannel) {
+  const grpc_arg* addr_arg =
+      grpc_channel_args_find(subchannel->args, GRPC_ARG_SUBCHANNEL_ADDRESS);
+  const char* addr_str = grpc_channel_arg_get_string(addr_arg);
+  GPR_ASSERT(addr_str != nullptr);  // Should have been set by LB policy.
+  return addr_str;
+}
+
 const char* grpc_get_subchannel_address_uri_arg(const grpc_channel_args* args) {
   const grpc_arg* addr_arg =
       grpc_channel_args_find(args, GRPC_ARG_SUBCHANNEL_ADDRESS);
@@ -786,9 +809,12 @@ grpc_arg grpc_create_subchannel_address_arg(const grpc_resolved_address* addr) {
 
 namespace grpc_core {
 
-ConnectedSubchannel::ConnectedSubchannel(grpc_channel_stack* channel_stack)
+ConnectedSubchannel::ConnectedSubchannel(
+    grpc_channel_stack* channel_stack,
+    channelz::SubchannelNode* channelz_subchannel)
     : RefCountedWithTracing<ConnectedSubchannel>(&grpc_trace_stream_refcount),
-      channel_stack_(channel_stack) {}
+      channel_stack_(channel_stack),
+      channelz_subchannel_(channelz_subchannel) {}
 
 ConnectedSubchannel::~ConnectedSubchannel() {
   GRPC_CHANNEL_STACK_UNREF(channel_stack_, "connected_subchannel_dtor");