From 3767568aaacc205450c686174d0dc2a2d2b1e005 Mon Sep 17 00:00:00 2001
From: Lubomír Sedlář <lsedlar@redhat.com>
Date: Aug 17 2018 12:47:07 +0000
Subject: symlink: Update latest symlink atomically


Instead of deleting the conflicting file first and linked after, create
a temporary link and move it over the target file.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

---

diff --git a/compose_utils/symlink.py b/compose_utils/symlink.py
index cd22141..c64989d 100644
--- a/compose_utils/symlink.py
+++ b/compose_utils/symlink.py
@@ -1,6 +1,5 @@
 # -*- coding: utf-8 -*-
 
-import errno
 import os
 import productmd
 
@@ -13,16 +12,13 @@ class ComposeSymlink(object):
 
     def _link(self, name):
         """Create a symbolic link with given name at the same location as the
-        compose. Existing file at the given path will be deleted.
+        compose. Existing file at the given path will be deleted atomically.
         """
-        symlink = os.path.join(self.path, '..', name)
-        try:
-            os.unlink(symlink)
-        except OSError as exc:
-            if exc.errno != errno.ENOENT:
-                raise
-
-        os.symlink(os.path.basename(self.path), symlink)
+        temp = os.path.join(self.path, "..", ".%s.tmp" % name)
+        symlink = os.path.join(self.path, "..", name)
+
+        os.symlink(os.path.basename(self.path), temp)
+        os.rename(temp, symlink)
 
     def get_latest_link_name(self, minor_version=False):
         """Get name of latest- symlink for current compose."""