Better debouncing of bokeh server callbacks

holoviews/plotting/bokeh/callbacks.py

@@ -14,6 +14,7 @@
 from panel.io.state import state
 from panel.callbacks import PeriodicCallback
 from pyviz_comms import JS_CALLBACK
+from tornado import gen
 
 from ...core import OrderedDict
 from ...core.options import CallbackError
@@ -339,38 +340,30 @@ def resolve_attr_spec(cls, spec, cb_obj, model=None):
                 resolved = getattr(resolved, p, None)
         return {'id': model.ref['id'], 'value': resolved}
 
+    def _schedule_callback(self, cb):
+        PeriodicCallback(callback=cb, period=50, count=1).start()
 
     def on_change(self, attr, old, new):
         """
         Process change events adding timeout to process multiple concerted
         value change at once rather than firing off multiple plot updates.
         """
         self._queue.append((attr, old, new))
-        if self._batched and not all(b in [q[0] for q in self._queue] for b in self._batched):
-            return # Skip until all batched events have arrived
-
         if not self._active and self.plot.document:
             self._active = True
-            if self.plot.document.session_context:
-                self.plot.document.add_timeout_callback(self.process_on_change, 50)
-            else:
-                PeriodicCallback(callback=self.process_on_change, period=50, count=1).start()
-
+            self._schedule_callback(self.process_on_change)
 
     def on_event(self, event):
         """
         Process bokeh UIEvents adding timeout to process multiple concerted
         value change at once rather than firing off multiple plot updates.
         """
-        self._queue.append((event))
+        self._queue.append(event)
         if not self._active and self.plot.document:
             self._active = True
-            if self.plot.document.session_context:
-                self.plot.document.add_timeout_callback(self.process_on_event, 50)
-            else:
-                PeriodicCallback(callback=self.process_on_event, period=50, count=1).start()
-
+            self._schedule_callback(self.process_on_event)
 
+    @gen.coroutine
     def process_on_event(self):
         """
         Trigger callback change event and triggering corresponding streams.
@@ -390,17 +383,16 @@ def process_on_event(self):
                 model_obj = self.plot_handles.get(self.models[0])
                 msg[attr] = self.resolve_attr_spec(path, event, model_obj)
             self.on_msg(msg)
+        self._schedule_callback(self.process_on_event)
 
-        if self.plot.document.session_context:
-            self.plot.document.add_timeout_callback(self.process_on_event, 50)
-        else:
-            PeriodicCallback(callback=self.process_on_event, period=50, count=1).start()
-
-
+    @gen.coroutine
     def process_on_change(self):
         if not self._queue:
             self._active = False
             return
+        elif self._batched and not all(b in [q[0] for q in self._queue] for b in self._batched):
+            self._schedule_callback(self.process_on_change)
+            return # Skip until all batched events have arrived
         self._queue = []
 
         msg = {}
@@ -422,10 +414,7 @@ def process_on_change(self):
             self.on_msg(msg)
             self._prev_msg = msg
 
-        if self.plot.document.session_context:
-            self.plot.document.add_timeout_callback(self.process_on_change, 50)
-        else:
-            PeriodicCallback(callback=self.process_on_change, period=100, count=1).start()
+        self._schedule_callback(self.process_on_change)
 
 
     def set_server_callback(self, handle):
@@ -798,7 +787,7 @@ class RangeXYCallback(Callback):
     on_changes = ['start', 'end']
 
     _batched = on_changes
-    
+
     def _process_msg(self, msg):
         data = {}
         if 'x0' in msg and 'x1' in msg:

holoviews/plotting/plot.py

@@ -143,11 +143,11 @@ def pane(self, pane):
                 if not plot.root:
                     continue
                 for cb in getattr(plot, 'callbacks', []):
-                    if hasattr(pane, '_on_error') and cb.comm:
+                    if hasattr(pane, '_on_error') and getattr(cb, 'comm', None):
                         cb.comm._on_error = partial(pane._on_error, plot.root.ref['id'])
         elif self.root:
             for cb in getattr(self, 'callbacks', []):
-                if hasattr(pane, '_on_error') and cb.comm:
+                if hasattr(pane, '_on_error') and getattr(cb, 'comm', None):
                     cb.comm._on_error = partial(pane._on_error, self.root.ref['id'])
 
     @property