Implement fallback for multiprocessing module

module is not working on Android

radicale/log.py

@@ -29,8 +29,11 @@ import logging
 import multiprocessing
 import os
 import sys
+import tempfile
 import threading
 
+from radicale import pathutils
+
 try:
     import systemd.journal
 except ImportError:
@@ -72,6 +75,27 @@ class IdentLogRecordFactory:
         return record
 
 
+class RwLockWrapper():
+
+    def __init__(self):
+        self._file = tempfile.NamedTemporaryFile()
+        self._lock = pathutils.RwLock(self._file.name)
+        self._cm = None
+
+    def acquire(self, blocking=True):
+        assert self._cm is None
+        if not blocking:
+            raise NotImplementedError
+        cm = self._lock.acquire("w")
+        cm.__enter__()
+        self._cm = cm
+
+    def release(self):
+        assert self._cm is not None
+        self._cm.__exit__(None, None, None)
+        self._cm = None
+
+
 class ThreadStreamsHandler(logging.Handler):
 
     terminator = "\n"
@@ -83,7 +107,11 @@ class ThreadStreamsHandler(logging.Handler):
         self.fallback_handler = fallback_handler
 
     def createLock(self):
+        try:
             self.lock = multiprocessing.Lock()
+        except Exception:
+            # HACK: Workaround for Android
+            self.lock = RwLockWrapper()
 
     def setFormatter(self, form):
         super().setFormatter(form)

radicale/server.py

@@ -30,6 +30,7 @@ import socket
 import socketserver
 import ssl
 import sys
+import threading
 import wsgiref.simple_server
 from configparser import ConfigParser
 from urllib.parse import unquote
@@ -42,7 +43,14 @@ try:
 except ImportError:
     systemd = None
 
-if hasattr(os, "fork"):
+USE_FORKING = hasattr(os, "fork")
+try:
+    multiprocessing.BoundedSemaphore()
+except Exception:
+    # HACK: Workaround for Android
+    USE_FORKING = False
+
+if USE_FORKING:
     ParallelizationMixIn = socketserver.ForkingMixIn
 else:
     ParallelizationMixIn = socketserver.ThreadingMixIn
@@ -84,9 +92,12 @@ class ParallelHTTPServer(ParallelizationMixIn,
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
+        if USE_FORKING:
+            sema_class = multiprocessing.BoundedSemaphore
+        else:
+            sema_class = threading.BoundedSemaphore
         if self.max_connections:
-            self.connections_guard = multiprocessing.BoundedSemaphore(
-                self.max_connections)
+            self.connections_guard = sema_class(self.max_connections)
         else:
             # use dummy context manager
             self.connections_guard = contextlib.ExitStack()