Implement multi-app workflows

dev-requirements.txt

@@ -15,7 +15,7 @@ Flask>=1.1
 # needed for auto fix
 ruff===0.2.2
 # needed for dapr-ext-workflow
-durabletask-dapr >= 0.2.0a8
+durabletask-dapr >= 0.2.0a9
 # needed for .env file loading in examples
 python-dotenv>=1.0.0
 # needed for enhanced schema generation from function features

examples/workflow/README.md

@@ -20,7 +20,7 @@ pip3 install -r requirements.txt
 Each of the examples in this directory can be run directly from the command line.
 
 ### Simple Workflow
-This example represents a workflow that manages counters through a series of activities and child workflows. 
+This example represents a workflow that manages counters through a series of activities and child workflows.
 It shows several Dapr Workflow features including:
 - Basic activity execution with counter increments
 - Retryable activities with configurable retry policies
@@ -269,4 +269,44 @@ When you run the example, you will see output like this:
 *** Calling child workflow 29a7592a1e874b07aad2bb58de309a51-child
 *** Child workflow 6feadc5370184b4998e50875b20084f6 called
 ...
-```
+```
+
+
+### Cross-app Workflow
+
+This example demonstrates how to call child workflows and activities in different apps. The multiple Dapr CLI instances can be started using the following commands:
+
+<!-- STEP
+name: Run apps
+expected_stdout_lines:
+  - '== APP == app1 - triggering app1 workflow'
+  - '== APP == app1 - received workflow call'
+  - '== APP == app1 - triggering app2 workflow'
+  - '== APP == app2 - received workflow call'
+  - '== APP == app2 - triggering app3 activity'
+  - '== APP == app3 - received activity call'
+  - '== APP == app3 - returning activity result'
+  - '== APP == app2 - received activity result'
+  - '== APP == app2 - returning workflow result'
+  - '== APP == app1 - received workflow result'
+  - '== APP == app1 - returning workflow result'
+background: true
+sleep: 5
+-->
+
+```sh
+pip install ./ext/dapr-ext-workflow
+dapr run --app-id wfexample3 --dapr-grpc-port 50003 python3 cross-app3.py &
+dapr run --app-id wfexample2 --dapr-grpc-port 50002 python3 cross-app2.py &
+dapr run --app-id wfexample1 --dapr-grpc-port 50001 python3 cross-app1.py
+```
+<!-- END_STEP -->
+
+When you run the apps, you will see output like this:
+```
+...
+app1 - triggering app2 workflow
+app2 - triggering app3 activity
+...
+```
+among others. This shows that the workflow calls are working as expected.

examples/workflow/cross-app1.py

@@ -0,0 +1,46 @@
+# -*- coding: utf-8 -*-
+# Copyright 2025 The Dapr Authors
+# Licensed 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.
+
+import dapr.ext.workflow as wf
+import time
+
+wfr = wf.WorkflowRuntime()
+
+
+@wfr.workflow
+def app1_workflow(ctx: wf.DaprWorkflowContext):
+    print(f'app1 - received workflow call', flush=True)
+    print(f'app1 - triggering app2 workflow', flush=True)
+
+    yield ctx.call_child_workflow(
+        workflow='app2_workflow',
+        input=None,
+        app_id='wfexample2',
+    )
+    print(f'app1 - received workflow result', flush=True)
+    print(f'app1 - returning workflow result', flush=True)
+
+    return 1
+
+
+if __name__ == '__main__':
+    wfr.start()
+    time.sleep(10)  # wait for workflow runtime to start
+
+    wf_client = wf.DaprWorkflowClient()
+    print(f'app1 - triggering app1 workflow', flush=True)
+    instance_id = wf_client.schedule_new_workflow(workflow=app1_workflow)
+
+    # Wait for the workflow to complete
+    time.sleep(5)
+
+    wfr.shutdown()

examples/workflow/cross-app2.py

@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+# Copyright 2025 The Dapr Authors
+# Licensed 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.
+
+import dapr.ext.workflow as wf
+import time
+
+wfr = wf.WorkflowRuntime()
+
+
+@wfr.workflow
+def app2_workflow(ctx: wf.DaprWorkflowContext):
+    print(f'app2 - received workflow call', flush=True)
+    print(f'app2 - triggering app3 activity', flush=True)
+    yield ctx.call_activity('app3_activity', input=None, app_id='wfexample3')
+    print(f'app2 - received activity result', flush=True)
+    print(f'app2 - returning workflow result', flush=True)
+
+    return 2
+
+
+if __name__ == '__main__':
+    wfr.start()
+    time.sleep(15)  # wait for workflow runtime to start
+    wfr.shutdown()

examples/workflow/cross-app3.py

@@ -0,0 +1,29 @@
+# -*- coding: utf-8 -*-
+# Copyright 2025 The Dapr Authors
+# Licensed 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.
+
+import dapr.ext.workflow as wf
+import time
+
+wfr = wf.WorkflowRuntime()
+
+
+@wfr.activity
+def app3_activity(ctx: wf.DaprWorkflowContext) -> int:
+    print(f'app3 - received activity call', flush=True)
+    print(f'app3 - returning activity result', flush=True)
+    return 3
+
+
+if __name__ == '__main__':
+    wfr.start()
+    time.sleep(15)  # wait for workflow runtime to start
+    wfr.shutdown()

ext/dapr-ext-workflow/dapr/ext/workflow/dapr_workflow_context.py

@@ -63,29 +63,68 @@ def create_timer(self, fire_at: Union[datetime, timedelta]) -> task.Task:
 
     def call_activity(
         self,
-        activity: Callable[[WorkflowActivityContext, TInput], TOutput],
+        activity: Union[Callable[[WorkflowActivityContext, TInput], TOutput], str],
         *,
         input: TInput = None,
         retry_policy: Optional[RetryPolicy] = None,
+        app_id: Optional[str] = None,
     ) -> task.Task[TOutput]:
+        # Handle string activity names for cross-app scenarios
+        if isinstance(activity, str):
+            activity_name = activity
+            if app_id is not None:
+                self._logger.debug(
+                    f'{self.instance_id}: Creating cross-app activity {activity_name} for app {app_id}'
+                )
+            else:
+                self._logger.debug(f'{self.instance_id}: Creating activity {activity_name}')
+
+            if retry_policy is None:
+                return self.__obj.call_activity(activity=activity_name, input=input, app_id=app_id)
+            return self.__obj.call_activity(
+                activity=activity_name, input=input, retry_policy=retry_policy.obj, app_id=app_id
+            )
+
+        # Handle function activity objects (original behavior)
         self._logger.debug(f'{self.instance_id}: Creating activity {activity.__name__}')
         if hasattr(activity, '_dapr_alternate_name'):
             act = activity.__dict__['_dapr_alternate_name']
         else:
             # this case should ideally never happen
             act = activity.__name__
         if retry_policy is None:
-            return self.__obj.call_activity(activity=act, input=input)
-        return self.__obj.call_activity(activity=act, input=input, retry_policy=retry_policy.obj)
+            return self.__obj.call_activity(activity=act, input=input, app_id=app_id)
+        return self.__obj.call_activity(
+            activity=act, input=input, retry_policy=retry_policy.obj, app_id=app_id
+        )
 
     def call_child_workflow(
         self,
-        workflow: Workflow,
+        workflow: Union[Workflow, str],
         *,
         input: Optional[TInput] = None,
         instance_id: Optional[str] = None,
         retry_policy: Optional[RetryPolicy] = None,
+        app_id: Optional[str] = None,
     ) -> task.Task[TOutput]:
+        # Handle string workflow names for cross-app scenarios
+        if isinstance(workflow, str):
+            workflow_name = workflow
+            self._logger.debug(f'{self.instance_id}: Creating child workflow {workflow_name}')
+
+            if retry_policy is None:
+                return self.__obj.call_sub_orchestrator(
+                    workflow_name, input=input, instance_id=instance_id, app_id=app_id
+                )
+            return self.__obj.call_sub_orchestrator(
+                workflow_name,
+                input=input,
+                instance_id=instance_id,
+                retry_policy=retry_policy.obj,
+                app_id=app_id,
+            )
+
+        # Handle function workflow objects (original behavior)
         self._logger.debug(f'{self.instance_id}: Creating child workflow {workflow.__name__}')
 
         def wf(ctx: task.OrchestrationContext, inp: TInput):
@@ -100,9 +139,11 @@ def wf(ctx: task.OrchestrationContext, inp: TInput):
             # this case should ideally never happen
             wf.__name__ = workflow.__name__
         if retry_policy is None:
-            return self.__obj.call_sub_orchestrator(wf, input=input, instance_id=instance_id)
+            return self.__obj.call_sub_orchestrator(
+                wf, input=input, instance_id=instance_id, app_id=app_id
+            )
         return self.__obj.call_sub_orchestrator(
-            wf, input=input, instance_id=instance_id, retry_policy=retry_policy.obj
+            wf, input=input, instance_id=instance_id, retry_policy=retry_policy.obj, app_id=app_id
         )
 
     def wait_for_external_event(self, name: str) -> task.Task:

ext/dapr-ext-workflow/dapr/ext/workflow/workflow_context.py

@@ -107,18 +107,22 @@ def create_timer(self, fire_at: Union[datetime, timedelta]) -> task.Task:
 
     @abstractmethod
     def call_activity(
-        self, activity: Activity[TOutput], *, input: Optional[TInput] = None
+        self,
+        activity: Union[Activity[TOutput], str],
+        *,
+        input: Optional[TInput] = None,
+        app_id: Optional[str] = None,
     ) -> task.Task[TOutput]:
         """Schedule an activity for execution.
 
         Parameters
         ----------
-        activity: Activity[TInput, TOutput]
-            A reference to the activity function to call.
+        activity: Activity[TInput, TOutput] | str
+            A reference to the activity function to call, or a string name for cross-app activities.
         input: TInput | None
             The JSON-serializable input (or None) to pass to the activity.
-        return_type: task.Task[TOutput]
-            The JSON-serializable output type to expect from the activity result.
+        app_id: str | None
+            The AppID that will execute the activity.
 
         Returns
         -------
@@ -130,22 +134,25 @@ def call_activity(
     @abstractmethod
     def call_child_workflow(
         self,
-        orchestrator: Workflow[TOutput],
+        orchestrator: Union[Workflow[TOutput], str],
         *,
         input: Optional[TInput] = None,
         instance_id: Optional[str] = None,
+        app_id: Optional[str] = None,
     ) -> task.Task[TOutput]:
         """Schedule child-workflow function for execution.
 
         Parameters
         ----------
-        orchestrator: Orchestrator[TInput, TOutput]
-            A reference to the orchestrator function to call.
+        orchestrator: Orchestrator[TInput, TOutput] | str
+            A reference to the orchestrator function to call, or a string name for cross-app workflows.
         input: TInput
             The optional JSON-serializable input to pass to the orchestrator function.
         instance_id: str
             A unique ID to use for the sub-orchestration instance. If not specified, a
             random UUID will be used.
+        app_id: str
+            The AppID that will execute the workflow.
 
         Returns
         -------

ext/dapr-ext-workflow/setup.cfg

@@ -25,11 +25,11 @@ packages = find_namespace:
 include_package_data = True
 install_requires =
     dapr >= 1.16.0
-    durabletask-dapr >= 0.2.0a8
+    durabletask-dapr >= 0.2.0a9
 
 [options.packages.find]
 include =
     dapr.*
 
-exclude = 
+exclude =
     tests

ext/dapr-ext-workflow/tests/test_dapr_workflow_context.py

@@ -36,10 +36,10 @@ def __init__(self):
     def create_timer(self, fire_at):
         return mock_create_timer
 
-    def call_activity(self, activity, input):
+    def call_activity(self, activity, input, app_id):
         return mock_call_activity
 
-    def call_sub_orchestrator(self, orchestrator, input, instance_id):
+    def call_sub_orchestrator(self, orchestrator, input, instance_id, app_id):
         return mock_call_sub_orchestrator
 
     def set_custom_status(self, custom_status):