diff --git a/taskflow/engines/worker_based/executor.py b/taskflow/engines/worker_based/executor.py
index a55229f1..7722432f 100644
--- a/taskflow/engines/worker_based/executor.py
+++ b/taskflow/engines/worker_based/executor.py
@@ -62,7 +62,8 @@ class WorkerTaskExecutor(executor.TaskExecutor):
         # pre-existing knowledge of the topics those workers are on to gather
         # and update this information).
         self._finder = wt.ProxyWorkerFinder(uuid, self._proxy, topics)
-        self._finder.on_worker = self._on_worker
+        self._finder.notifier.register(wt.WorkerFinder.WORKER_ARRIVED,
+                                       self._on_worker)
         self._helpers = tu.ThreadBundle()
         self._helpers.bind(lambda: tu.daemon_thread(self._proxy.start),
                            after_start=lambda t: self._proxy.wait(),
@@ -74,8 +75,9 @@ class WorkerTaskExecutor(executor.TaskExecutor):
                                after_join=lambda t: p_worker.reset(),
                                before_start=lambda t: p_worker.reset())
 
-    def _on_worker(self, worker):
+    def _on_worker(self, event_type, details):
         """Process new worker that has arrived (and fire off any work)."""
+        worker = details['worker']
         for request in self._requests_cache.get_waiting_requests(worker):
             if request.transition_and_log_error(pr.PENDING, logger=LOG):
                 self._publish_request(request, worker)
diff --git a/taskflow/engines/worker_based/types.py b/taskflow/engines/worker_based/types.py
index 70185d52..3d53e87a 100644
--- a/taskflow/engines/worker_based/types.py
+++ b/taskflow/engines/worker_based/types.py
@@ -26,6 +26,7 @@ import six
 from taskflow.engines.worker_based import protocol as pr
 from taskflow import logging
 from taskflow.types import cache as base
+from taskflow.types import notifier
 from taskflow.types import periodic
 from taskflow.types import timing as tt
 from taskflow.utils import kombu_utils as ku
@@ -99,9 +100,12 @@ class TopicWorker(object):
 class WorkerFinder(object):
     """Base class for worker finders..."""
 
+    #: Event type emitted when a new worker arrives.
+    WORKER_ARRIVED = 'worker_arrived'
+
     def __init__(self):
         self._cond = threading.Condition()
-        self.on_worker = None
+        self.notifier = notifier.RestrictedNotifier([self.WORKER_ARRIVED])
 
     @abc.abstractmethod
     def _total_workers(self):
@@ -214,8 +218,8 @@ class ProxyWorkerFinder(WorkerFinder):
                           " total workers are currently known)", worker,
                           self._total_workers())
                 self._cond.notify_all()
-        if self.on_worker is not None and new_or_updated:
-            self.on_worker(worker)
+        if new_or_updated:
+            self.notifier.notify(self.WORKER_ARRIVED, {'worker': worker})
 
     def clear(self):
         with self._cond: