Switch to use manual constructor

src/core/lib/channel/channel_tracer.cc

@@ -56,11 +56,13 @@ struct TraceEvent {
 };
 
 ChannelTracer::ChannelTracer(size_t max_nodes)
-    : num_nodes_logged_(0),
+    : channel_uuid_(-1),
+      num_nodes_logged_(0),
       list_size_(0),
       max_list_size_(max_nodes),
       head_trace_(0),
       tail_trace_(0) {
+  if (!max_list_size_) return;  // tracing is disabled if max_nodes == 0
   gpr_mu_init(&tracer_mu_);
   gpr_ref_init(&refs_, 1);
   channel_uuid_ = grpc_object_registry_register_object(
@@ -70,6 +72,7 @@ ChannelTracer::ChannelTracer(size_t max_nodes)
 }
 
 ChannelTracer* ChannelTracer::Ref() {
+  if (!max_list_size_) return nullptr;  // tracing is disabled if max_nodes == 0
   gpr_ref(&refs_);
   return this;
 }
@@ -84,6 +87,7 @@ void ChannelTracer::FreeNode(TraceEvent* node) {
 }
 
 void ChannelTracer::Unref() {
+  if (!max_list_size_) return;  // tracing is disabled if max_nodes == 0
   if (gpr_unref(&refs_)) {
     TraceEvent* it = head_trace_;
     while (it != nullptr) {
@@ -100,6 +104,7 @@ intptr_t ChannelTracer::GetUuid() { return channel_uuid_; }
 void ChannelTracer::AddTrace(grpc_slice data, grpc_error* error,
                              grpc_connectivity_state connectivity_state,
                              ChannelTracer* referenced_tracer) {
+  if (!max_list_size_) return;  // tracing is disabled if max_nodes == 0
   ++num_nodes_logged_;
   // create and fill up the new node
   TraceEvent* new_trace_node =
@@ -254,6 +259,7 @@ class ChannelTracerRenderer {
 };
 
 char* ChannelTracer::RenderTrace(bool recursive) {
+  if (!max_list_size_) return nullptr;  // tracing is disabled if max_nodes == 0
   ChannelTracerRenderer renderer(this, recursive);
   return renderer.Run();
 }

src/core/lib/surface/channel.cc

@@ -32,6 +32,7 @@
 #include "src/core/lib/debug/stats.h"
 #include "src/core/lib/iomgr/iomgr.h"
 #include "src/core/lib/slice/slice_internal.h"
+#include "src/core/lib/support/manual_constructor.h"
 #include "src/core/lib/support/memory.h"
 #include "src/core/lib/support/object_registry.h"
 #include "src/core/lib/support/string.h"
@@ -63,7 +64,7 @@ struct grpc_channel {
   gpr_mu registered_call_mu;
   registered_call* registered_calls;
 
-  grpc_core::ChannelTracer* tracer;
+  grpc_core::ManualConstructor<grpc_core::ChannelTracer> tracer;
 
   char* target;
 };
@@ -103,7 +104,7 @@ grpc_channel* grpc_channel_create_with_builder(
   memset(channel, 0, sizeof(*channel));
   channel->target = target;
   channel->is_client = grpc_channel_stack_type_is_client(channel_stack_type);
-  channel->tracer = nullptr;
+  bool tracer_initialized = false;
   gpr_mu_init(&channel->registered_call_mu);
   channel->registered_calls = nullptr;
 
@@ -195,15 +196,13 @@ grpc_channel* grpc_channel_create_with_builder(
           0x1; /* always support no compression */
     } else if (0 ==
                strcmp(args->args[i].key, GRPC_ARG_CHANNEL_TRACING_MAX_NODES)) {
-      GPR_ASSERT(channel->tracer == nullptr);
+      GPR_ASSERT(!tracer_initialized);
+      tracer_initialized = true;
       // max_nodes defaults to 10, clamped between 0 and 100.
       const grpc_integer_options options = {10, 0, 100};
       size_t max_nodes =
           (size_t)grpc_channel_arg_get_integer(&args->args[i], options);
-      if (max_nodes > 0) {
+      channel->tracer.Init(max_nodes);
-        channel->tracer = grpc_core::New<grpc_core::ChannelTracer>(
-            max_nodes);  // TODO(ncteisen): leaky yo
-      }
     }
   }
 
@@ -214,7 +213,7 @@ grpc_channel* grpc_channel_create_with_builder(
 }
 
 char* grpc_channel_get_trace(grpc_channel* channel, bool recursive) {
-  return channel->tracer ? channel->tracer->RenderTrace(recursive) : nullptr;
+  return channel->tracer->RenderTrace(recursive);
 }
 
 grpc_channel* grpc_channel_create(const char* target,

test/core/channel/channel_tracer_test.cc

@@ -41,6 +41,7 @@ static void add_simple_trace(ChannelTracer* tracer) {
 static void validate_tracer(ChannelTracer* tracer,
                             size_t expected_num_nodes_logged,
                             size_t max_nodes) {
+  if (!max_nodes) return;
   char* json_str = tracer->RenderTrace(true);
   grpc_json* json = grpc_json_parse_string(json_str);
   validate_channel_data(json, expected_num_nodes_logged,
@@ -51,6 +52,7 @@ static void validate_tracer(ChannelTracer* tracer,
 
 static void validate_tracer_data_matches_uuid_lookup(ChannelTracer* tracer) {
   intptr_t uuid = tracer->GetUuid();
+  if (uuid == -1) return;  // Doesn't make sense to lookup if tracing disabled
   char* tracer_json_str = tracer->RenderTrace(true);
   char* uuid_lookup_json_str =
       ChannelTracer::GetChannelTraceFromUuid(uuid, true);