src: Node Tracing Controller

This commit adds support for trace-event tracing to Node.js. It provides
a mechanism to centralize tracing information generated by V8, Node
core, and userspace code. It includes:

 - A trace writer responsible for serializing traces and cycling the
   output files so that no individual file becomes to large.
 - A buffer for aggregating traces to allow for batched flushes.
 - An agent which initializes the tracing controller and ensures that
   trace serialization is done on a separate thread.
 - A set of macros for generating trace events.
 - Tests and documentation.

Author: Raymond Kang <raymondksi@gmail.com>
Author: Kelvin Jin <kelvinjin@google.com>
Author: Matthew Loring <mattloring@google.com>
Author: Jason Ginchereau <jasongin@microsoft.com>

PR-URL: https://github.com/nodejs/node/pull/9304

Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Josh Gavant <josh.gavant@outlook.com>

1 files changed, 74 insertions, 0 deletions

diff --git a/src/tracing/node_trace_writer.h b/src/tracing/node_trace_writer.h
new file mode 100644
index 0000000000..5813db0ab1
--- /dev/null
+++ b/src/tracing/node_trace_writer.h
@@ -0,0 +1,74 @@
+#ifndef SRC_NODE_TRACE_WRITER_H_
+#define SRC_NODE_TRACE_WRITER_H_
+
+#include <sstream>
+#include <queue>
+
+#include "node_mutex.h"
+#include "libplatform/v8-tracing.h"
+#include "uv.h"
+
+namespace node {
+namespace tracing {
+
+using v8::platform::tracing::TraceObject;
+using v8::platform::tracing::TraceWriter;
+using v8::platform::tracing::TracingController;
+
+class NodeTraceWriter : public TraceWriter {
+ public:
+  NodeTraceWriter(uv_loop_t* tracing_loop);
+  ~NodeTraceWriter();
+
+  void AppendTraceEvent(TraceObject* trace_event) override;
+  void Flush() override;
+  void Flush(bool blocking);
+
+  static const int kTracesPerFile = 1 << 19;
+
+ private:
+  struct WriteRequest {
+    uv_fs_t req;
+    NodeTraceWriter* writer;
+    std::string str;
+    int highest_request_id;
+  };
+
+  static void WriteCb(uv_fs_t* req);
+  void OpenNewFileForStreaming();
+  void WriteToFile(std::string&& str, int highest_request_id);
+  void WriteSuffix();
+  static void FlushSignalCb(uv_async_t* signal);
+  void FlushPrivate();
+  static void ExitSignalCb(uv_async_t* signal);
+
+  uv_loop_t* tracing_loop_;
+  // Triggers callback to initiate writing the contents of stream_ to disk.
+  uv_async_t flush_signal_;
+  // Triggers callback to close async objects, ending the tracing thread.
+  uv_async_t exit_signal_;
+  // Prevents concurrent R/W on state related to serialized trace data
+  // before it's written to disk, namely stream_ and total_traces_.
+  Mutex stream_mutex_;
+  // Prevents concurrent R/W on state related to write requests.
+  Mutex request_mutex_;
+  // Allows blocking calls to Flush() to wait on a condition for
+  // trace events to be written to disk.
+  ConditionVariable request_cond_;
+  // Used to wait until async handles have been closed.
+  ConditionVariable exit_cond_;
+  int fd_ = -1;
+  std::queue<WriteRequest*> write_req_queue_;
+  int num_write_requests_ = 0;
+  int highest_request_id_completed_ = 0;
+  int total_traces_ = 0;
+  int file_num_ = 0;
+  std::ostringstream stream_;
+  TraceWriter* json_trace_writer_ = nullptr;
+  bool exited_ = false;
+};
+
+}  // namespace tracing
+}  // namespace node
+
+#endif  // SRC_NODE_TRACE_WRITER_H_