--- /dev/null
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Orchestrator events.
+"""
+
+from blinker import signal
+
+# workflow engine task signals:
+sent_task_signal = signal('sent_task_signal')
+start_task_signal = signal('start_task_signal')
+on_success_task_signal = signal('success_task_signal')
+on_failure_task_signal = signal('failure_task_signal')
+
+# workflow engine workflow signals:
+start_workflow_signal = signal('start_workflow_signal')
+on_cancelling_workflow_signal = signal('on_cancelling_workflow_signal')
+on_cancelled_workflow_signal = signal('on_cancelled_workflow_signal')
+on_success_workflow_signal = signal('on_success_workflow_signal')
+on_failure_workflow_signal = signal('on_failure_workflow_signal')
+on_resume_workflow_signal = signal('on_resume_workflow_signal')