From 04321739c2231a1e24b9bec4fc33726ee7395ee4 Mon Sep 17 00:00:00 2001
From: Hariharan Devarajan <mani.hariharan@gmail.com>
Date: Wed, 9 Aug 2023 21:41:56 -0700
Subject: [PATCH] bug fix for multi thread appends

---
 src/dlio_profiler/writer/chrome_writer.cpp | 27 +++++++++++-----------
 src/dlio_profiler/writer/chrome_writer.h   |  2 +-
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/src/dlio_profiler/writer/chrome_writer.cpp b/src/dlio_profiler/writer/chrome_writer.cpp
index 9416ceae..ea830781 100644
--- a/src/dlio_profiler/writer/chrome_writer.cpp
+++ b/src/dlio_profiler/writer/chrome_writer.cpp
@@ -22,21 +22,11 @@ void dlio_profiler::ChromeWriter::initialize(char *filename, bool throw_error) {
 void
 dlio_profiler::ChromeWriter::log(std::string &event_name, std::string &category, TimeResolution &start_time, TimeResolution &duration,
                                  std::unordered_map<std::string, std::any> &metadata, int process_id) {
-  if (is_first_write) {
-    if (this->fp == NULL) {
-      fp = fopen(filename.c_str(), "w+");
-    }
+  if (this->fp == nullptr) {
+    fp = fopen(filename.c_str(), "a+");
     if (fp == nullptr) {
       ERROR(fp == nullptr,"unable to create log file %s", filename.c_str());
-    } else {
-      std::string data = "[\n";
-      auto written_elements = fwrite(data.c_str(), data.size(), sizeof(char), fp);
-      fflush(fp);
-      if (written_elements != 1) {
-        ERROR(written_elements != 1, "unable to initialize log file %s", filename.c_str());
-      }
     }
-    is_first_write = false;
   }
   if (fp != nullptr) {
     std::string json = convert_json(event_name, category, start_time, duration, metadata, process_id);
@@ -46,11 +36,21 @@ dlio_profiler::ChromeWriter::log(std::string &event_name, std::string &category,
       ERROR(written_elements != 1, "unable to write to log file %s", filename.c_str());
     }
   }
+  is_first_write = false;
 }
 
 void dlio_profiler::ChromeWriter::finalize() {
   if (fp != nullptr) {
-    int status = fclose(fp);
+    int status = fseek(fp, 0, SEEK_SET);
+    if (status != 0) {
+      ERROR(status != -1, "unable to seek to start log file %d", filename.c_str());
+    }
+    std::string data = "[\n";
+    auto written_elements = fwrite(data.c_str(), data.size(), sizeof(char), fp);
+    if (written_elements != 1) {
+      ERROR(written_elements != 1, "unable to initialize log file %s", filename.c_str());
+    }
+    status = fclose(fp);
     if (status != 0) {
       ERROR(status != -1, "unable to close log file %d", filename.c_str());
     }
@@ -74,6 +74,7 @@ dlio_profiler::ChromeWriter::convert_json(std::string &event_name, std::string &
   }
   auto start_sec = std::chrono::duration<TimeResolution, std::ratio<1>>(start_time);
   auto duration_sec = std::chrono::duration<TimeResolution, std::ratio<1>>(duration);
+  if (is_first_write) all_stream << "  ";
   all_stream  << R"({"name":")" << event_name << "\","
               << R"("cat":")" << category << "\","
               << "\"pid\":" << pid << ","
diff --git a/src/dlio_profiler/writer/chrome_writer.h b/src/dlio_profiler/writer/chrome_writer.h
index a03c3f47..18e5570e 100644
--- a/src/dlio_profiler/writer/chrome_writer.h
+++ b/src/dlio_profiler/writer/chrome_writer.h
@@ -38,7 +38,7 @@ namespace dlio_profiler {
           return std::string(hostname);
         }
     public:
-        ChromeWriter(FILE* fp=NULL):BaseWriter(), is_first_write(true), mtx_map(){
+        ChromeWriter(FILE* fp=nullptr):BaseWriter(), is_first_write(true), mtx_map(){
           process_id = getpid();
           this->fp = fp;
           hwloc_topology_init(&topology);  // initialization