file locking enhancements

ubiquerg/files.py

@@ -111,6 +111,8 @@ def wait_for_lock(lock_file, wait_max=30):
     first_message_flag = False
     dot_count = 0
     totaltime = 0
+    if os.path.isfile(lock_file):
+        ori_timestamp = os.path.getmtime(lock_file)
     while os.path.isfile(lock_file):
         if first_message_flag is False:
             sys.stdout.write("Waiting for file lock: {} ".format(lock_file))
@@ -125,8 +127,16 @@ def wait_for_lock(lock_file, wait_max=30):
         totaltime += sleeptime
         sleeptime = min((sleeptime + .1) * 1.25, 10)
         if totaltime >= wait_max:
-            raise RuntimeError("The maximum wait time ({}) has been reached and the "
-                               "lock file still exists.".format(wait_max))
+            if os.path.isfile(lock_file):
+                timestamp = os.path.getmtime(lock_file)
+                if timestamp > ori_timestamp:
+                    ori_timestamp = timestamp
+                    totaltime = 0
+                    sleeptime = 0
+                    continue
+                raise RuntimeError(
+                    "The maximum wait time ({}) has been reached and the lock "
+                    "file still exists.".format(wait_max))
     if first_message_flag:
         print(" File unlocked")
 
@@ -178,29 +188,37 @@ def remove_lock(filepath):
     return False
 
 
-def create_lock(filepath, wait_max=10):
-    """
-    Securely create a lock file
-
-    :param str filepath: path to a file to lock
-    :param int wait_max: max wait time if the file in question is already locked
-    """
-    lock_path = make_lock_path(filepath)
-    # wait until no lock is present
-    wait_for_lock(lock_path, wait_max)
-    # attempt to lock the file
+def _create_lock(lock_path, filepath, wait_max):
     try:
         create_file_racefree(lock_path)
     except FileNotFoundError:
         parent_dir = os.path.dirname(filepath)
         os.makedirs(parent_dir)
-        create_file_racefree(lock_path)
+        _create_lock(lock_path, filepath, wait_max)
     except Exception as e:
         if e.errno == errno.EEXIST:
             # Rare case: file already exists;
-            # the lock has been created in the split second since the last lock existence check,
-            # wait for the lock file to be gone, but no longer than `wait_max`.
+            # the lock has been created in the split second since the
+            # last lock existence check,
+            # wait for the lock file to be gone, but no longer than
+            # `wait_max`.
+            print(
+                "The lock has been created in the split second since the "
+                "last lock existence check. Waiting")
             wait_for_lock(lock_path, wait_max)
-            create_file_racefree(lock_path)
+            _create_lock(lock_path, filepath, wait_max)
         else:
             raise e
+
+
+def create_lock(filepath, wait_max=10):
+    """
+    Securely create a lock file
+
+    :param str filepath: path to a file to lock
+    :param int wait_max: max wait time if the file in question is already locked
+    """
+    lock_path = make_lock_path(filepath)
+    # wait until no lock is present
+    wait_for_lock(lock_path, wait_max)
+    _create_lock(lock_path, filepath, wait_max)