Add option to disable syncing to disk

Disabling syncing increases the risk of data loss when the system crashes or power fails. On the positive it can increase the performance to a great extent.

config

@@ -103,6 +103,11 @@
 # Folder for storing local collections, created if not present
 #filesystem_folder = ~/.config/radicale/collections
 
+# Sync all changes to disk during requests. (This can impair performance.)
+# Disabling it increases the risk of data loss, when the system crashes or
+# power fails!
+#fsync = True
+
 # Command that is run after changes to storage
 #hook =
 # Example: git add -A && (git diff --cached --quiet || git commit -m "Changes by "%(user)s)

radicale/config.py

@@ -58,6 +58,7 @@ INITIAL_CONFIG = {
         "type": "multifilesystem",
         "filesystem_folder": os.path.expanduser(
             "~/.config/radicale/collections"),
+        "fsync": "True",
         "hook": ""},
     "logging": {
         "config": "/etc/radicale/logging",

radicale/storage.py

@@ -393,6 +393,7 @@ class Collection(BaseCollection):
                                  delete=False, prefix=".Radicale.tmp-")
         try:
             yield tmp
+            if self.configuration.getboolean("storage", "fsync"):
                 if os.name == "posix" and hasattr(fcntl, "F_FULLFSYNC"):
                     fcntl.fcntl(tmp.fileno(), fcntl.F_FULLFSYNC)
                 else:
@@ -413,13 +414,15 @@ class Collection(BaseCollection):
                 return file_name
         raise FileExistsError(errno.EEXIST, "No usable file name found")
 
-    @staticmethod
-    def _sync_directory(path):
+    @classmethod
+    def _sync_directory(cls, path):
         """Sync directory to disk.
 
         This only works on POSIX and does nothing on other systems.
 
         """
+        if not cls.configuration.getboolean("storage", "fsync"):
+            return
         if os.name == "posix":
             fd = os.open(path, 0)
             try: