src: trace_event: secondary storage for metadata

Metadata trace-events should be held in secondary storage so that they
can be periodically reemitted. This change establishes the secondary
storage and ensures that events are reemitted on each flush.

PR-URL: https://github.com/nodejs/node/pull/20900
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

4 files changed, 78 insertions, 18 deletions

diff --git a/src/tracing/agent.cc b/src/tracing/agent.cc
index fd5cb3387b..103df55da5 100644
--- a/src/tracing/agent.cc
+++ b/src/tracing/agent.cc
@@ -1,6 +1,7 @@
 #include "tracing/agent.h"
 
 #include <string>
+#include "trace_event.h"
 #include "tracing/node_trace_buffer.h"
 #include "debug_utils.h"
 #include "env-inl.h"
@@ -207,9 +208,35 @@ void Agent::AppendTraceEvent(TraceObject* trace_event) {
 }
 
 void Agent::Flush(bool blocking) {
+  for (const auto& event : metadata_events_)
+    AppendTraceEvent(event.get());
+
   for (const auto& id_writer : writers_)
     id_writer.second->Flush(blocking);
 }
 
+void TracingController::AddMetadataEvent(
+    const unsigned char* category_group_enabled,
+    const char* name,
+    int num_args,
+    const char** arg_names,
+    const unsigned char* arg_types,
+    const uint64_t* arg_values,
+    std::unique_ptr<v8::ConvertableToTraceFormat>* convertable_values,
+    unsigned int flags) {
+  std::unique_ptr<TraceObject> trace_event(new TraceObject);
+  trace_event->Initialize(
+      TRACE_EVENT_PHASE_METADATA, category_group_enabled, name,
+      node::tracing::kGlobalScope,  // scope
+      node::tracing::kNoId,         // id
+      node::tracing::kNoId,         // bind_id
+      num_args, arg_names, arg_types, arg_values, convertable_values,
+      TRACE_EVENT_FLAG_NONE,
+      CurrentTimestampMicroseconds(),
+      CurrentCpuTimestampMicroseconds());
+  node::tracing::TraceEventHelper::GetAgent()->AddMetadataEvent(
+      std::move(trace_event));
+}
+
 }  // namespace tracing
 }  // namespace node
diff --git a/src/tracing/agent.h b/src/tracing/agent.h
index e9f52abe64..db5e2a6bfd 100644
--- a/src/tracing/agent.h
+++ b/src/tracing/agent.h
@@ -7,6 +7,7 @@
 #include "util.h"
 #include "node_mutex.h"
 
+#include <list>
 #include <set>
 #include <string>
 #include <unordered_map>
@@ -34,6 +35,15 @@ class TracingController : public v8::platform::tracing::TracingController {
   int64_t CurrentTimestampMicroseconds() override {
     return uv_hrtime() / 1000;
   }
+  void AddMetadataEvent(
+      const unsigned char* category_group_enabled,
+      const char* name,
+      int num_args,
+      const char** arg_names,
+      const unsigned char* arg_types,
+      const uint64_t* arg_values,
+      std::unique_ptr<v8::ConvertableToTraceFormat>* convertable_values,
+      unsigned int flags);
 };
 
 class AgentWriterHandle {
@@ -93,6 +103,10 @@ class Agent {
 
   // Writes to all writers registered through AddClient().
   void AppendTraceEvent(TraceObject* trace_event);
+
+  void AddMetadataEvent(std::unique_ptr<TraceObject> event) {
+    metadata_events_.push_back(std::move(event));
+  }
   // Flushes all writers registered through AddClient().
   void Flush(bool blocking);
 
@@ -131,6 +145,7 @@ class Agent {
   ConditionVariable initialize_writer_condvar_;
   uv_async_t initialize_writer_async_;
   std::set<AsyncTraceWriter*> to_be_initialized_;
+  std::list<std::unique_ptr<TraceObject>> metadata_events_;
 };
 
 void AgentWriterHandle::reset() {
diff --git a/src/tracing/trace_event.cc b/src/tracing/trace_event.cc
index f661dd5c69..9232c34c4c 100644
--- a/src/tracing/trace_event.cc
+++ b/src/tracing/trace_event.cc
@@ -3,14 +3,18 @@
 namespace node {
 namespace tracing {
 
-v8::TracingController* g_controller = nullptr;
+Agent* g_agent = nullptr;
 
-void TraceEventHelper::SetTracingController(v8::TracingController* controller) {
-  g_controller = controller;
+void TraceEventHelper::SetAgent(Agent* agent) {
+  g_agent = agent;
 }
 
-v8::TracingController* TraceEventHelper::GetTracingController() {
-  return g_controller;
+Agent* TraceEventHelper::GetAgent() {
+  return g_agent;
+}
+
+TracingController* TraceEventHelper::GetTracingController() {
+  return g_agent->GetTracingController();
 }
 
 }  // namespace tracing
diff --git a/src/tracing/trace_event.h b/src/tracing/trace_event.h
index 1165fca59a..d5d4befb14 100644
--- a/src/tracing/trace_event.h
+++ b/src/tracing/trace_event.h
@@ -310,8 +310,9 @@ const uint64_t kNoId = 0;
 
 class TraceEventHelper {
  public:
-  static v8::TracingController* GetTracingController();
-  static void SetTracingController(v8::TracingController* controller);
+  static TracingController* GetTracingController();
+  static Agent* GetAgent();
+  static void SetAgent(Agent* agent);
 };
 
 // TraceID encapsulates an ID that can either be an integer or pointer. Pointers
@@ -487,6 +488,26 @@ static V8_INLINE uint64_t AddTraceEventWithTimestampImpl(
       arg_names, arg_types, arg_values, arg_convertables, flags, timestamp);
 }
 
+static V8_INLINE void AddMetadataEventImpl(
+    const uint8_t* category_group_enabled, const char* name, int32_t num_args,
+    const char** arg_names, const uint8_t* arg_types,
+    const uint64_t* arg_values, unsigned int flags) {
+  std::unique_ptr<v8::ConvertableToTraceFormat> arg_convertibles[2];
+  if (num_args > 0 && arg_types[0] == TRACE_VALUE_TYPE_CONVERTABLE) {
+    arg_convertibles[0].reset(reinterpret_cast<v8::ConvertableToTraceFormat*>(
+        static_cast<intptr_t>(arg_values[0])));
+  }
+  if (num_args > 1 && arg_types[1] == TRACE_VALUE_TYPE_CONVERTABLE) {
+    arg_convertibles[1].reset(reinterpret_cast<v8::ConvertableToTraceFormat*>(
+        static_cast<intptr_t>(arg_values[1])));
+  }
+  node::tracing::TracingController* controller =
+      node::tracing::TraceEventHelper::GetTracingController();
+  return controller->AddMetadataEvent(
+      category_group_enabled, name, num_args, arg_names, arg_types, arg_values,
+      arg_convertibles, flags);
+}
+
 // Define SetTraceValue for each allowed type. It stores the type and
 // value in the return arguments. This allows this API to avoid declaring any
 // structures so that it is portable to third_party libraries.
@@ -632,23 +653,16 @@ static V8_INLINE uint64_t AddTraceEventWithTimestamp(
 }
 
 template <class ARG1_TYPE>
-static V8_INLINE uint64_t AddMetadataEvent(
+static V8_INLINE void AddMetadataEvent(
     const uint8_t* category_group_enabled, const char* name,
     const char* arg1_name, ARG1_TYPE&& arg1_val) {
   const int num_args = 1;
   uint8_t arg_type;
   uint64_t arg_value;
   SetTraceValue(std::forward<ARG1_TYPE>(arg1_val), &arg_type, &arg_value);
-  // TODO(ofrobots): It would be good to add metadata events to a separate
-  // buffer so that they can be periodically reemitted. For now, we have a
-  // single buffer, so we just add them to the main buffer.
-  return TRACE_EVENT_API_ADD_TRACE_EVENT(
-      TRACE_EVENT_PHASE_METADATA,
-      category_group_enabled, name,
-      node::tracing::kGlobalScope,  // scope
-      node::tracing::kNoId,         // id
-      node::tracing::kNoId,         // bind_id
-      num_args, &arg1_name, &arg_type, &arg_value, TRACE_EVENT_FLAG_NONE);
+  AddMetadataEventImpl(
+      category_group_enabled, name, num_args, &arg1_name, &arg_type, &arg_value,
+      TRACE_EVENT_FLAG_NONE);
 }
 
 // Used by TRACE_EVENTx macros. Do not use directly.