debounce multiple modified events that occur at a same moment

docker_volume_watcher/container_notifier.py

@@ -5,11 +5,43 @@
 import logging
 from os.path import relpath
 import posixpath
+import time
 
 import docker
 from watchdog.observers import Observer
 from watchdog.events import PatternMatchingEventHandler
 
+def debounce(bounce_delay):
+    """
+    define debounce method annotation
+
+    Args:
+        bounce_delay (int): the minimum delay in seconds between two function calls
+    """
+
+    def decorate(my_function):
+        """
+        Decorator ensures function that can only be called once every `bounce_delay` seconds.
+
+        Args:
+            my_function (function): the function to debounce
+        """
+
+        old_time = {'value' : None}
+
+        def wrapped(*args, **kwargs):
+            """
+            internal function
+            """
+            new_time = time.time()
+            if old_time['value'] is None or new_time - old_time['value'] >= bounce_delay:
+                result = my_function(*args, **kwargs)
+                old_time['value'] = time.time()
+                return result
+            return None
+        return wrapped
+    return decorate
+
 class NonZeroExitError(RuntimeError):
     """
     A non-zero exit code error from the command execution in docker.
@@ -54,6 +86,10 @@ def __init__(self, container, host_dir, container_dir, exclude_patterns=None):
     def __str__(self):
         return '%s -> %s:%s' % (self.host_dir, self.container.name, self.container_dir)
 
+    # debounce avoid two subsequents save to ooccur
+    # limitation, if several files are saved the same time
+    # some files could be skipped
+    @debounce(2)
     def __change_handler(self, event):
         host_path = event.dest_path if hasattr(event, 'dest_path') else event.src_path
         relative_host_path = relpath(host_path, self.host_dir).replace('\\', '/')