Allow EventLogger to directly log from a JSONWriter.

Summary:
Allow EventLogger to directly log from a JSONWriter.  This allows
the JSONWriter to be shared by EventLogger and potentially EventListener,
which is an important step to integrate EventLogger and EventListener.

This patch also rewrites EventLoggerHelpers::LogTableFileCreation(),
which uses the new API to generate identical log.

Test Plan:
Run db_bench in debug mode and make sure the log is correct and no
assertions fail.

Reviewers: sdong, anthony, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D38709

db/event_logger_helpers.cc

@@ -11,22 +11,34 @@ namespace {
 inline double SafeDivide(double a, double b) { return b == 0.0 ? 0 : a / b; }
 }  // namespace
 
+void EventLoggerHelpers::AppendCurrentTime(JSONWriter* jwriter) {
+  *jwriter << "time_micros"
+           << std::chrono::duration_cast<std::chrono::microseconds>(
+                  std::chrono::system_clock::now().time_since_epoch()).count();
+}
+
 void EventLoggerHelpers::LogTableFileCreation(
     EventLogger* event_logger, int job_id, uint64_t file_number,
     uint64_t file_size, const TableProperties& table_properties) {
-  auto stream = event_logger->Log();
-  stream << "job" << job_id << "event"
-         << "table_file_creation"
-         << "file_number" << file_number << "file_size" << file_size
-         << "table_properties";
-  stream.StartObject();
+  JSONWriter jwriter;
+  AppendCurrentTime(&jwriter);
+  jwriter << "job" << job_id
+           << "event" << "table_file_creation"
+           << "file_number" << file_number
+           << "file_size" << file_size;
+
+  // table_properties
+  {
+    jwriter << "table_properties";
+    jwriter.StartObject();
 
     // basic properties:
-  stream << "data_size" << table_properties.data_size
+    jwriter << "data_size" << table_properties.data_size
             << "index_size" << table_properties.index_size
             << "filter_size" << table_properties.filter_size
             << "raw_key_size" << table_properties.raw_key_size
-         << "raw_average_key_size" << SafeDivide(table_properties.raw_key_size,
+            << "raw_average_key_size" << SafeDivide(
+                table_properties.raw_key_size,
                 table_properties.num_entries)
             << "raw_value_size" << table_properties.raw_value_size
             << "raw_average_value_size" << SafeDivide(
@@ -37,10 +49,12 @@ void EventLoggerHelpers::LogTableFileCreation(
 
     // user collected properties
     for (const auto& prop : table_properties.user_collected_properties) {
-    stream << prop.first << prop.second;
+      jwriter << prop.first << prop.second;
+    }
+    jwriter.EndObject();
   }
 
-  stream.EndObject();
+  event_logger->Log(jwriter);
 }
 
 }  // namespace rocksdb

db/event_logger_helpers.h

@@ -11,6 +11,7 @@ namespace rocksdb {
 
 class EventLoggerHelpers {
  public:
+  static void AppendCurrentTime(JSONWriter* json_writer);
   static void LogTableFileCreation(EventLogger* event_logger, int job_id,
                                    uint64_t file_number, uint64_t file_size,
                                    const TableProperties& table_properties);

util/event_logger.cc

@@ -18,7 +18,6 @@
 
 namespace rocksdb {
 
-const char* kEventLoggerPrefix = "EVENT_LOG_v1";
 
 EventLoggerStream::EventLoggerStream(Logger* logger)
     : logger_(logger), log_buffer_(nullptr), json_writer_(nullptr) {}
@@ -33,14 +32,35 @@ EventLoggerStream::~EventLoggerStream() {
     printf("%s\n", json_writer_->Get().c_str());
 #else
     if (logger_) {
-      Log(logger_, "%s %s", kEventLoggerPrefix, json_writer_->Get().c_str());
+      EventLogger::Log(logger_, *json_writer_);
     } else if (log_buffer_) {
-      LogToBuffer(log_buffer_, "%s %s", kEventLoggerPrefix,
-                  json_writer_->Get().c_str());
+      EventLogger::LogToBuffer(log_buffer_, *json_writer_);
     }
 #endif
     delete json_writer_;
   }
 }
 
+void EventLogger::Log(const JSONWriter& jwriter) {
+  Log(logger_, jwriter);
+}
+
+void EventLogger::Log(Logger* logger, const JSONWriter& jwriter) {
+#ifdef ROCKSDB_PRINT_EVENTS_TO_STDOUT
+  printf("%s\n", jwriter.Get().c_str());
+#else
+  rocksdb::Log(logger, "%s %s", Prefix(), jwriter.Get().c_str());
+#endif
+}
+
+void EventLogger::LogToBuffer(
+    LogBuffer* log_buffer, const JSONWriter& jwriter) {
+#ifdef ROCKSDB_PRINT_EVENTS_TO_STDOUT
+  printf("%s\n", jwriter.Get().c_str());
+#else
+  assert(log_buffer);
+  rocksdb::LogToBuffer(log_buffer, "%s %s", Prefix(), jwriter.Get().c_str());
+#endif
+}
+
 }  // namespace rocksdb

util/event_logger.h

@@ -157,11 +157,18 @@ class EventLoggerStream {
 // "file_size": 1909699}
 class EventLogger {
  public:
+  static const char* Prefix() {
+    return "EVENT_LOG_v1";
+  }
+
   explicit EventLogger(Logger* logger) : logger_(logger) {}
   EventLoggerStream Log() { return EventLoggerStream(logger_); }
   EventLoggerStream LogToBuffer(LogBuffer* log_buffer) {
     return EventLoggerStream(log_buffer);
   }
+  void Log(const JSONWriter& jwriter);
+  static void Log(Logger* logger, const JSONWriter& jwriter);
+  static void LogToBuffer(LogBuffer* log_buffer, const JSONWriter& jwriter);
 
  private:
   Logger* logger_;