Don't drop temporary files all over the place

When renaming a file over another which is the same hard link, the
rename is a no-op. This left many temporary files in /var/log/hosts
because a file is attempted to be synced (and thus hard-linked between
dated and undated file names) over a couple of days. The solution to
this is how the `ln` command does it: rename, then unlink the temporary
file.

Signed-off-by: Nils Philippsen <nils@redhat.com>

roles/web-data-analysis/files/sync-http-logs.py

@@ -67,8 +67,17 @@ def link_force_atomic(src, dst):
             # ignore if the file exists, just try another file name
             pass
         else:
-            # no exception: linking succeeded, rename & break out of the loop
+            # no exception: linking to temp file succeeded, rename it over dst
             os.rename(tmpdst, dst)
+
+            # if tmpdst and dst are the same hard link, unlink tmpdst here because os.rename() would
+            # have been a no-op
+            try:
+                os.unlink(tmpdst)
+            except FileNotFoundError:
+                # os.rename() above wasn't a no-op, i.e. tmpdst was renamed already
+                pass
+
             break