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
@@ -57,7 +57,7 @@ timeout_seconds: 30
 -->
 
 ```sh
-dapr run --app-id wf-simple-example --dapr-grpc-port 50001 -- python3 simple.py
+dapr run --app-id wf-simple-example -- python3 simple.py
 ```
 <!--END_STEP-->
 
@@ -99,7 +99,7 @@ timeout_seconds: 30
 -->
 
 ```sh
-dapr run --app-id wfexample --dapr-grpc-port 50001 -- python3 task_chaining.py
+dapr run --app-id wfexample -- python3 task_chaining.py
 ```
 <!--END_STEP-->
 
@@ -146,7 +146,7 @@ timeout_seconds: 30
 -->
 
 ```sh
-dapr run --app-id wfexample --dapr-grpc-port 50001 -- python3 fan_out_fan_in.py
+dapr run --app-id wfexample -- python3 fan_out_fan_in.py
 ```
 <!--END_STEP-->
 
@@ -186,7 +186,7 @@ This example demonstrates how to use a workflow to interact with a human user. T
 The Dapr CLI can be started using the following command:
 
 ```sh
-dapr run --app-id wfexample --dapr-grpc-port 50001
+dapr run --app-id wfexample
 ```
 
 In a separate terminal window, run the following command to start the Python workflow app:
@@ -222,7 +222,7 @@ This example demonstrates how to eternally running workflow that polls an endpoi
 The Dapr CLI can be started using the following command:
 
 ```sh
-dapr run --app-id wfexample --dapr-grpc-port 50001
+dapr run --app-id wfexample
 ```
 
 In a separate terminal window, run the following command to start the Python workflow app:
@@ -254,7 +254,7 @@ This workflow runs forever or until you press `ENTER` to stop it. Starting the a
 This example demonstrates how to call a child workflow. The Dapr CLI can be started using the following command:
 
 ```sh
-dapr run --app-id wfexample --dapr-grpc-port 50001
+dapr run --app-id wfexample
 ```
 
 In a separate terminal window, run the following command to start the Python workflow app:
@@ -269,4 +269,129 @@ 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: 20
+-->
+
+```sh
+dapr run --app-id wfexample3 python3 cross-app3.py &
+dapr run --app-id wfexample2 python3 cross-app2.py &
+dapr run --app-id wfexample1 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.
+
+
+#### Error handling on activity calls
+
+This example demonstrates how the error handling works on activity calls across apps.
+
+Error handling on activity calls across apps works as normal workflow activity calls.
+
+In this example we run `app3` in failing mode, which makes the activity call return error constantly. The activity call from `app2` will fail after the retry policy is exhausted.
+
+<!-- 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 - raising error in activity due to error mode being enabled'
+  - '== APP == app2 - received activity error from app3'
+  - '== APP == app2 - returning workflow result'
+  - '== APP == app1 - received workflow result'
+  - '== APP == app1 - returning workflow result'
+sleep: 20
+-->
+
+```sh
+export ERROR_ACTIVITY_MODE=true
+dapr run --app-id wfexample3 python3 cross-app3.py &
+dapr run --app-id wfexample2 python3 cross-app2.py &
+dapr run --app-id wfexample1 python3 cross-app1.py
+```
+<!-- END_STEP -->
+
+
+When you run the apps with the `ERROR_ACTIVITY_MODE` environment variable set, you will see output like this:
+```
+...
+app3 - received activity call
+app3 - raising error in activity due to error mode being enabled
+app2 - received activity error from app3
+...
+```
+among others. This shows that the activity calls are failing as expected, and they are being handled as expected too.
+
+
+#### Error handling on workflow calls
+
+This example demonstrates how the error handling works on workflow calls across apps.
+
+Error handling on workflow calls across apps works as normal workflow calls.
+
+In this example we run `app2` in failing mode, which makes the workflow call return error constantly. The workflow call from `app1` will fail after the retry policy is exhausted.
+
+<!-- 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 - raising error in workflow due to error mode being enabled'
+  - '== APP == app1 - received workflow error from app2'
+  - '== APP == app1 - returning workflow result'
+sleep: 20
+-->
+
+```sh
+export ERROR_WORKFLOW_MODE=true
+dapr run --app-id wfexample3 python3 cross-app3.py &
+dapr run --app-id wfexample2 python3 cross-app2.py &
+dapr run --app-id wfexample1 python3 cross-app1.py
+```
+<!-- END_STEP -->
+
+When you run the apps with the `ERROR_WORKFLOW_MODE` environment variable set, you will see output like this:
+```
+...
+app2 - received workflow call
+app2 - raising error in workflow due to error mode being enabled
+app1 - received workflow error from app2
+...
+```
+among others. This shows that the workflow calls are failing as expected, and they are being handled as expected too.
+

examples/workflow/cross-app1.py

@@ -0,0 +1,58 @@
+# -*- 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.
+
+from datetime import timedelta
+
+from durabletask.task import TaskFailedError
+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)
+
+    try:
+        retry_policy = wf.RetryPolicy(
+            max_number_of_attempts=2,
+            first_retry_interval=timedelta(milliseconds=100),
+            max_retry_interval=timedelta(seconds=3),
+        )
+        yield ctx.call_child_workflow(
+            workflow='app2_workflow',
+            input=None,
+            app_id='wfexample2',
+            retry_policy=retry_policy,
+        )
+        print(f'app1 - received workflow result', flush=True)
+    except TaskFailedError as e:
+        print(f'app1 - received workflow error from app2', 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(7)
+
+    wfr.shutdown()

examples/workflow/cross-app2.py

@@ -0,0 +1,50 @@
+# -*- 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.
+
+from datetime import timedelta
+import os
+
+from durabletask.task import TaskFailedError
+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)
+    if os.getenv('ERROR_WORKFLOW_MODE', 'false') == 'true':
+        print(f'app2 - raising error in workflow due to error mode being enabled', flush=True)
+        raise ValueError('Error in workflow due to error mode being enabled')
+    print(f'app2 - triggering app3 activity', flush=True)
+    try:
+        retry_policy = wf.RetryPolicy(
+            max_number_of_attempts=2,
+            first_retry_interval=timedelta(milliseconds=100),
+            max_retry_interval=timedelta(seconds=3),
+        )
+        result = yield ctx.call_activity(
+            'app3_activity', input=None, app_id='wfexample3', retry_policy=retry_policy
+        )
+        print(f'app2 - received activity result', flush=True)
+    except TaskFailedError as e:
+        print(f'app2 - received activity error from app3', 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 +1,32 @@
+# -*- 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 os
+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)
+    if os.getenv('ERROR_ACTIVITY_MODE', 'false') == 'true':
+        print(f'app3 - raising error in activity due to error mode being enabled', flush=True)
+        raise ValueError('Error in activity due to error mode being enabled')
+    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()