3 files changed, 21 insertions, 4 deletions
diff --git a/src/node_trace_events.cc b/src/node_trace_events.cc
index 9538e75d2c..6a0d4f037a 100644
--- a/src/node_trace_events.cc
+++ b/src/node_trace_events.cc
@@ -74,6 +74,9 @@ void NodeCategorySet::Enable(const FunctionCallbackInfo<Value>& args) {
   CHECK_NOT_NULL(category_set);
   const auto& categories = category_set->GetCategories();
   if (!category_set->enabled_ && !categories.empty()) {
+    // Starts the Tracing Agent if it wasn't started already (e.g. through
+    // a command line flag.)
+    StartTracingAgent();
     GetTracingAgentWriter()->Enable(categories);
     category_set->enabled_ = true;
   }
diff --git a/src/node_v8_platform-inl.h b/src/node_v8_platform-inl.h
index ed91ee3a02..2c89ee9e52 100644
--- a/src/node_v8_platform-inl.h
+++ b/src/node_v8_platform-inl.h
@@ -85,7 +85,11 @@ struct V8Platform {
         tracing_agent_->GetTracingController();
     trace_state_observer_.reset(new NodeTraceStateObserver(controller));
     controller->AddTraceStateObserver(trace_state_observer_.get());
-    StartTracingAgent();
+    tracing_file_writer_ = tracing_agent_->DefaultHandle();
+    // Only start the tracing agent if we enabled any tracing categories.
+    if (!per_process::cli_options->trace_event_categories.empty()) {
+      StartTracingAgent();
+    }
     // Tracing must be initialized before platform threads are created.
     platform_ = new NodePlatform(thread_pool_size, controller);
     v8::V8::InitializePlatform(platform_);
@@ -111,9 +115,9 @@ struct V8Platform {
   }
 
   inline void StartTracingAgent() {
-    if (per_process::cli_options->trace_event_categories.empty()) {
-      tracing_file_writer_ = tracing_agent_->DefaultHandle();
-    } else {
+    // Attach a new NodeTraceWriter only if this function hasn't been called
+    // before.
+    if (tracing_file_writer_.IsDefaultHandle()) {
       std::vector<std::string> categories =
           SplitString(per_process::cli_options->trace_event_categories, ',');
 
@@ -163,6 +167,10 @@ namespace per_process {
 extern struct V8Platform v8_platform;
 }
 
+inline void StartTracingAgent() {
+  return per_process::v8_platform.StartTracingAgent();
+}
+
 inline tracing::AgentWriterHandle* GetTracingAgentWriter() {
   return per_process::v8_platform.GetTracingAgentWriter();
 }
diff --git a/src/tracing/agent.h b/src/tracing/agent.h
index 2e95e38582..0039cc3679 100644
--- a/src/tracing/agent.h
+++ b/src/tracing/agent.h
@@ -59,6 +59,8 @@ class AgentWriterHandle {
   inline void Enable(const std::set<std::string>& categories);
   inline void Disable(const std::set<std::string>& categories);
 
+  inline bool IsDefaultHandle();
+
   inline Agent* agent() { return agent_; }
 
   inline v8::TracingController* GetTracingController();
@@ -175,6 +177,10 @@ void AgentWriterHandle::Disable(const std::set<std::string>& categories) {
   if (agent_ != nullptr) agent_->Disable(id_, categories);
 }
 
+bool AgentWriterHandle::IsDefaultHandle() {
+  return agent_ != nullptr && id_ == Agent::kDefaultHandleId;
+}
+
 inline v8::TracingController* AgentWriterHandle::GetTracingController() {
   return agent_ != nullptr ? agent_->GetTracingController() : nullptr;
 }