From 33a4d428f943ea49121ce0fa3daa702f3c43271a Mon Sep 17 00:00:00 2001
From: Arseny Smirnov <arseny30@gmail.com>
Date: Fri, 16 Feb 2018 12:13:04 +0300
Subject: [PATCH] Binlog: call fsync only if it is necessary

GitOrigin-RevId: 2081799ad27c62950d029ebeb13d19f343be024d
---
 tddb/td/db/binlog/Binlog.cpp | 28 +++++++++++++++++++---------
 tddb/td/db/binlog/Binlog.h   |  1 +
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/tddb/td/db/binlog/Binlog.cpp b/tddb/td/db/binlog/Binlog.cpp
index 675c78f52..5d76028db 100644
--- a/tddb/td/db/binlog/Binlog.cpp
+++ b/tddb/td/db/binlog/Binlog.cpp
@@ -258,10 +258,12 @@ Status Binlog::close(bool need_sync) {
     path_ = "";
     info_.is_opened = false;
     fd_.close();
+    need_sync_ = false;
   };
-  flush();
   if (need_sync) {
-    TRY_STATUS(fd_.sync());
+    sync();
+  } else {
+    flush();
   }
   return Status::OK();
 }
@@ -353,7 +355,11 @@ void Binlog::do_event(BinlogEvent &&event) {
 
 void Binlog::sync() {
   flush();
-  fd_.sync().ensure();
+  if (need_sync_) {
+    auto status = fd_.sync();
+    LOG_IF(FATAL, status.is_error()) << "Failed to sync binlog: " << status;
+    need_sync_ = false;
+  }
 }
 
 void Binlog::flush() {
@@ -365,8 +371,14 @@ void Binlog::flush() {
   if (byte_flow_flag_) {
     byte_flow_source_.wakeup();
   }
-  fd_.flush_write().ensure();
+  auto r_written = fd_.flush_write();
+  r_written.ensure();
+  auto written = r_written.ok();
+  if (written > 0) {
+    need_sync_ = true;
+  }
   need_flush_since_ = 0;
+  LOG_IF(FATAL, fd_.need_flush_write()) << "Failed to flush binlog";
 }
 
 void Binlog::lazy_flush() {
@@ -584,13 +596,11 @@ void Binlog::do_reindex() {
   processor_->for_each([&](BinlogEvent &event) {
     do_event(std::move(event));  // NB: no move is actually happens
   });
-  flush();
-  LOG_IF(FATAL, fd_.need_flush_write()) << "Reindex failed: failed to flush everything on disk";
-  auto status = fd_.sync();
-  LOG_IF(FATAL, status.is_error()) << "Failed to sync binlog: " << status;
+  need_sync_ = true;  // must sync creation of the file
+  sync();
 
   // finish_reindex
-  status = unlink(path_);
+  auto status = unlink(path_);
   LOG_IF(FATAL, status.is_error()) << "Failed to unlink old binlog: " << status;
   status = rename(new_path, path_);
   LOG_IF(FATAL, status.is_error()) << "Failed to rename binlog: " << status;
diff --git a/tddb/td/db/binlog/Binlog.h b/tddb/td/db/binlog/Binlog.h
index 87aed9a7a..7a286f9e1 100644
--- a/tddb/td/db/binlog/Binlog.h
+++ b/tddb/td/db/binlog/Binlog.h
@@ -123,6 +123,7 @@ class Binlog {
   bool in_flush_events_buffer_{false};
   uint64 last_id_{0};
   double need_flush_since_ = 0;
+  bool need_sync_{false};
   enum class State { Empty, Load, Reindex, Run } state_{State::Empty};
 
   static constexpr uint32 MAX_EVENT_SIZE = 65536;