TST: make _do_test_lock_externally work on Windows

We need to access the platform-specific file handle locking
mechanisms, but they are hidden away in the class implementations.

This pushes them into static methods to make it easy to access them
while still allowing sub-classing.

fasteners/process_lock.py

@@ -214,32 +214,44 @@ class _InterProcessLock(object):
         return os.path.exists(self.path)
 
     def trylock(self):
-        raise NotImplementedError()
+        self._trylock(self.lockfile)
 
     def unlock(self):
+        self._unlock(self.lockfile)
+
+    @staticmethod
+    def _trylock():
+        raise NotImplementedError()
+
+    @staticmethod
+    def _unlock():
         raise NotImplementedError()
 
 
 class _WindowsLock(_InterProcessLock):
     """Interprocess lock implementation that works on windows systems."""
 
-    def trylock(self, lockfile=None):
-        fileno = (lockfile or self.lockfile).fileno()
+    @staticmethod
+    def _trylock(lockfile):
+        fileno = lockfile.fileno()
         msvcrt.locking(fileno, msvcrt.LK_NBLCK, 1)
 
-    def unlock(self, lockfile=None):
-        fileno = (lockfile or self.lockfile).fileno()
+    @staticmethod
+    def _unlock(lockfile):
+        fileno = lockfile.fileno()
         msvcrt.locking(fileno, msvcrt.LK_UNLCK, 1)
 
 
 class _FcntlLock(_InterProcessLock):
     """Interprocess lock implementation that works on posix systems."""
 
-    def trylock(self, lockfile=None):
-        fcntl.lockf(lockfile or self.lockfile, fcntl.LOCK_EX | fcntl.LOCK_NB)
+    @staticmethod
+    def _trylock(lockfile):
+        fcntl.lockf(lockfile, fcntl.LOCK_EX | fcntl.LOCK_NB)
 
-    def unlock(self, lockfile=None):
-        fcntl.lockf(lockfile or self.lockfile, fcntl.LOCK_UN)
+    @staticmethod
+    def _unlock(lockfile):
+        fcntl.lockf(lockfile, fcntl.LOCK_UN)
 
 
 if os.name == 'nt':

fasteners/tests/test_process_lock.py

@@ -55,6 +55,36 @@ def try_lock(lock_file):
         os._exit(0)
 
 
+def lock_files(lock_path, handles_dir, num_handles=50):
+    with pl.InterProcessLock(lock_path):
+
+        # Open some files we can use for locking
+        handles = []
+        for n in range(num_handles):
+            path = os.path.join(handles_dir, ('file-%s' % n))
+            handles.append(open(path, 'w'))
+
+        # Loop over all the handles and try locking the file
+        # without blocking, keep a count of how many files we
+        # were able to lock and then unlock. If the lock fails
+        # we get an IOError and bail out with bad exit code
+        count = 0
+        for handle in handles:
+            try:
+                pl.InterProcessLock._trylock(handle)
+                count += 1
+                pl.InterProcessLock._unlock(handle)
+            except IOError:
+                print(os.getpid())
+                os._exit(2)
+            finally:
+                handle.close()
+
+        # Check if we were able to open all files
+        if count != num_handles:
+            raise AssertionError("Unable to open all handles")
+
+
 class ProcessLockTest(test.TestCase):
     def setUp(self):
         super(ProcessLockTest, self).setUp()
@@ -111,49 +141,25 @@ class ProcessLockTest(test.TestCase):
     def _do_test_lock_externally(self, lock_dir):
         lock_path = os.path.join(lock_dir, "lock")
 
-        def lock_files(handles_dir):
-            with pl.InterProcessLock(lock_path):
-
-                # Open some files we can use for locking
-                handles = []
-                for n in range(50):
-                    path = os.path.join(handles_dir, ('file-%s' % n))
-                    handles.append(open(path, 'w'))
-
-                # Loop over all the handles and try locking the file
-                # without blocking, keep a count of how many files we
-                # were able to lock and then unlock. If the lock fails
-                # we get an IOError and bail out with bad exit code
-                count = 0
-                for handle in handles:
-                    try:
-                        pl.InterProcessLock.trylock(handle)
-                        count += 1
-                        pl.InterProcessLock.unlock(handle)
-                    except IOError:
-                        os._exit(2)
-                    finally:
-                        handle.close()
-
-                # Check if we were able to open all files
-                self.assertEqual(50, count)
-
         handles_dir = tempfile.mkdtemp()
         self.tmp_dirs.append(handles_dir)
-        children = []
-        for n in range(50):
-            pid = os.fork()
-            if pid:
-                children.append(pid)
-            else:
-                try:
-                    lock_files(handles_dir)
-                finally:
-                    os._exit(0)
-        for child in children:
-            (pid, status) = os.waitpid(child, 0)
-            if pid:
-                self.assertEqual(0, status)
+
+        num_handles = 50
+        num_processes = 50
+        args = [lock_path, handles_dir, num_handles]
+        children = [multiprocessing.Process(target=lock_files, args=args)
+                    for _ in range(num_processes)]
+
+        # We do this in three loops in an attempt to get all processes up and
+        # running at the same time
+        for c in children:
+            # Just a precaution to avoid hung processes
+            c.daemon = True
+            c.start()
+        for c in children:
+            c.join(10)
+        for c in children:
+            self.assertEqual(0, c.exitcode)
 
     def test_lock_externally(self):
         self._do_test_lock_externally(self.lock_dir)