src: trace_events: support for metadata events

Add support for metadata events. At this point they are added to the
main buffer. Emit a metadata event for the main thread.

PR-URL: https://github.com/nodejs/node/pull/20757
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/src/tracing/trace_event.h b/src/tracing/trace_event.h
index 3fbe1b0a1f..1165fca59a 100644
--- a/src/tracing/trace_event.h
+++ b/src/tracing/trace_event.h
@@ -118,6 +118,15 @@ enum CategoryGroupEnabledFlags {
   node::tracing::TraceEventHelper::GetTracingController()       \
       ->UpdateTraceEventDuration
 
+// Adds a metadata event to the trace log. The |AppendValueAsTraceFormat| method
+// on the convertable value will be called at flush time.
+// TRACE_EVENT_API_ADD_METADATA_EVENT(
+//     const unsigned char* category_group_enabled,
+//     const char* event_name,
+//     const char* arg_name,
+//     std::unique_ptr<ConvertableToTraceFormat> arg_value)
+#define TRACE_EVENT_API_ADD_METADATA_EVENT node::tracing::AddMetadataEvent
+
 // Defines atomic operations used internally by the tracing system.
 #define TRACE_EVENT_API_ATOMIC_WORD intptr_t
 #define TRACE_EVENT_API_ATOMIC_LOAD(var) (var)
@@ -259,6 +268,16 @@ enum CategoryGroupEnabledFlags {
     }                                                                        \
   } while (0)
 
+#define INTERNAL_TRACE_EVENT_METADATA_ADD(category_group, name, ...)  \
+  do { \
+    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
+    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
+      TRACE_EVENT_API_ADD_METADATA_EVENT( \
+          INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
+          ##__VA_ARGS__); \
+    } \
+  } while(0)
+
 // Enter and leave a context based on the current scope.
 #define INTERNAL_TRACE_EVENT_SCOPED_CONTEXT(category_group, name, context) \
   struct INTERNAL_TRACE_EVENT_UID(ScopedContext) {                         \
@@ -612,6 +631,26 @@ static V8_INLINE uint64_t AddTraceEventWithTimestamp(
       arg_names, arg_types, arg_values, flags, timestamp);
 }
 
+template <class ARG1_TYPE>
+static V8_INLINE uint64_t 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);
+}
+
 // Used by TRACE_EVENTx macros. Do not use directly.
 class ScopedTracer {
  public: