Merge pull request #19187 from bigfacebear/add_subchannel_tracer

add subchannel tracer

doc/environment_variables.md

@@ -74,6 +74,7 @@ some configuration as environment variables that can be set.
   - queue_pluck
   - server_channel - lightweight trace of significant server channel events
   - secure_endpoint - traces bytes flowing through encrypted channels
+  - subchannel - traces the connectivity state of subchannel
   - timer - timers (alarms) in the grpc internals
   - timer_check - more detailed trace of timer logic in grpc internals
   - transport_security - traces metadata about secure channel establishment
@@ -89,6 +90,7 @@ some configuration as environment variables that can be set.
   - pending_tags - traces still-in-progress tags on completion queues
   - polling - traces the selected polling engine
   - polling_api - traces the api calls to polling engine
+  - subchannel_refcount
   - queue_refcount
   - error_refcount
   - stream_refcount

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

@@ -75,6 +75,9 @@
 
 namespace grpc_core {
 
+TraceFlag grpc_trace_subchannel(false, "subchannel");
+DebugOnlyTraceFlag grpc_trace_subchannel_refcount(false, "subchannel_refcount");
+
 //
 // ConnectedSubchannel
 //
@@ -83,7 +86,7 @@ ConnectedSubchannel::ConnectedSubchannel(
     grpc_channel_stack* channel_stack, const grpc_channel_args* args,
     RefCountedPtr<channelz::SubchannelNode> channelz_subchannel,
     intptr_t socket_uuid)
-    : ConnectedSubchannelInterface(&grpc_trace_stream_refcount),
+    : ConnectedSubchannelInterface(&grpc_trace_subchannel_refcount),
       channel_stack_(channel_stack),
       args_(grpc_channel_args_copy(args)),
       channelz_subchannel_(std::move(channelz_subchannel)),
@@ -332,7 +335,7 @@ class Subchannel::ConnectedSubchannelStateWatcher {
         case GRPC_CHANNEL_TRANSIENT_FAILURE:
         case GRPC_CHANNEL_SHUTDOWN: {
           if (!c->disconnected_ && c->connected_subchannel_ != nullptr) {
-            if (grpc_trace_stream_refcount.enabled()) {
+            if (grpc_trace_subchannel.enabled()) {
               gpr_log(GPR_INFO,
                       "Connected subchannel %p of subchannel %p has gone into "
                       "%s. Attempting to reconnect.",
@@ -1106,7 +1109,7 @@ gpr_atm Subchannel::RefMutate(
   gpr_atm old_val = barrier ? gpr_atm_full_fetch_add(&ref_pair_, delta)
                             : gpr_atm_no_barrier_fetch_add(&ref_pair_, delta);
 #ifndef NDEBUG
-  if (grpc_trace_stream_refcount.enabled()) {
+  if (grpc_trace_subchannel_refcount.enabled()) {
     gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
             "SUBCHANNEL: %p %12s 0x%" PRIxPTR " -> 0x%" PRIxPTR " [%s]", this,
             purpose, old_val, old_val + delta, reason);