From 972c9cb37457c70530610c22a5f3ff68adf3bd5b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Va=CC=81clav=20Slavi=CC=81k?= <vaclav@slavik.io>
Date: Tue, 3 Feb 2015 18:22:25 +0100
Subject: [PATCH 1/6] Fix FSDirectory::sync() to sync writes to disk

Contrary to the documentation, FSDirectory::sync() conversion to C++
omitted the most important line of the Java original: actually fsyncing
the file descriptor. As the result, its current code amounts to little
more than a little nonsensical noop dance.

Add the missing fsync() call. Use fsync() on Unix, its
FlushFileBuffers() equivalent on Windows, and F_FULLFSYNC on OS X where
fsync() is documented as not always sufficient. F_FULLFSYNC is more
expensive than fsync(), but guarantees physical write; SQLite uses it
too.
---
 src/core/store/FSDirectory.cpp | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/src/core/store/FSDirectory.cpp b/src/core/store/FSDirectory.cpp
index 82b5736..2cb257a 100644
--- a/src/core/store/FSDirectory.cpp
+++ b/src/core/store/FSDirectory.cpp
@@ -5,7 +5,6 @@
 /////////////////////////////////////////////////////////////////////////////
 
 #include "LuceneInc.h"
-#include <boost/filesystem/fstream.hpp>
 #include "FSDirectory.h"
 #include "NativeFSLockFactory.h"
 #include "SimpleFSDirectory.h"
@@ -14,6 +13,15 @@
 #include "FileUtils.h"
 #include "StringUtils.h"
 
+#if defined(_WIN32)
+    #include <windows.h>
+#elif defined(__APPLE__)
+    #include <fcntl.h>
+#else
+    #include <unistd.h>
+#endif
+#include <boost/iostreams/device/file_descriptor.hpp>
+
 extern "C"
 {
 #include "../util/md5/md5.h"
@@ -148,15 +156,24 @@ void FSDirectory::sync(const String& name) {
     bool success = false;
 
     for (int32_t retryCount = 0; retryCount < 5; ++retryCount) {
-        boost::filesystem::ofstream syncFile;
+        boost::iostreams::file_descriptor syncFile;
         try {
-            syncFile.open(path, std::ios::binary | std::ios::in | std::ios::out);
+            syncFile.open(boost::filesystem::path(path));
         } catch (...) {
         }
 
         if (syncFile.is_open()) {
+            boost::iostreams::file_descriptor::handle_type fd = syncFile.handle();
+#if defined(_WIN32)
+            bool ok = ::FlushFileBuffers(fd) != 0;
+#elif defined(__APPLE__)
+            bool ok = fcntl(fd, F_FULLFSYNC) == 0;
+#else
+            bool ok = fsync(fd) == 0;
+#endif
             syncFile.close();
-            success = true;
+            if (ok)
+                success = true;
             break;
         }
 
-- 
2.3.6