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Merge pull request #3495 from greenie-msft/add_python_workflow_doc
Start of Python QS doc
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Hannah Hunter
GitHub
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45c23a8b38
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@ -28,7 +28,7 @@ In this guide, you'll:
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Currently, you can experience the Dapr Workflow using the .NET SDK.
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{{< tabs ".NET" >}}
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{{< tabs ".NET" "Python" >}}
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<!-- .NET -->
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{{% codetab %}}
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@ -254,8 +254,234 @@ The `Activities` directory holds the four workflow activities used by the workfl
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- `ProcessPaymentActivity.cs`
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- `UpdateInventoryActivity.cs`
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{{% /codetab %}}
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<!-- Python -->
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{{% codetab %}}
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### Step 1: Pre-requisites
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For this example, you will need:
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- [Dapr CLI and initialized environment](https://docs.dapr.io/getting-started).
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- [Python 3.7+ installed](https://www.python.org/downloads/).
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<!-- IGNORE_LINKS -->
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- [Docker Desktop](https://www.docker.com/products/docker-desktop)
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<!-- END_IGNORE -->
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### Step 2: Set up the environment
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Clone the [sample provided in the Quickstarts repo](https://github.com/dapr/quickstarts/tree/master/workflows).
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```bash
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git clone https://github.com/dapr/quickstarts.git
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```
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In a new terminal window, navigate to the `order-processor` directory:
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```bash
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cd workflows/python/sdk/order-processor
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```
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Install the Dapr Python SDK package:
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```bash
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pip3 install -r requirements.txt
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```
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### Step 3: Run the order processor app
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In the terminal, start the order processor app alongside a Dapr sidecar:
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```bash
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dapr run --app-id order-processor --resources-path ../../../components/ -- python3 app.py
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```
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> **Note:** Since Python3.exe is not defined in Windows, you may need to use `python app.py` instead of `python3 app.py`.
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This starts the `order-processor` app with unique workflow ID and runs the workflow activities.
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Expected output:
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```bash
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== APP == Starting order workflow, purchasing 10 of cars
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== APP == 2023-06-06 09:35:52.945 durabletask-worker INFO: Successfully connected to 127.0.0.1:65406. Waiting for work items...
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== APP == INFO:NotifyActivity:Received order f4e1926e-3721-478d-be8a-f5bebd1995da for 10 cars at $165000 !
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== APP == INFO:VerifyInventoryActivity:Verifying inventory for order f4e1926e-3721-478d-be8a-f5bebd1995da of 10 cars
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== APP == INFO:VerifyInventoryActivity:There are 100 Cars available for purchase
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== APP == INFO:RequestApprovalActivity:Requesting approval for payment of 165000 USD for 10 cars
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== APP == 2023-06-06 09:36:05.969 durabletask-worker INFO: f4e1926e-3721-478d-be8a-f5bebd1995da Event raised: manager_approval
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== APP == INFO:NotifyActivity:Payment for order f4e1926e-3721-478d-be8a-f5bebd1995da has been approved!
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== APP == INFO:ProcessPaymentActivity:Processing payment: f4e1926e-3721-478d-be8a-f5bebd1995da for 10 cars at 165000 USD
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== APP == INFO:ProcessPaymentActivity:Payment for request ID f4e1926e-3721-478d-be8a-f5bebd1995da processed successfully
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== APP == INFO:UpdateInventoryActivity:Checking inventory for order f4e1926e-3721-478d-be8a-f5bebd1995da for 10 cars
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== APP == INFO:UpdateInventoryActivity:There are now 90 cars left in stock
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== APP == INFO:NotifyActivity:Order f4e1926e-3721-478d-be8a-f5bebd1995da has completed!
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== APP == 2023-06-06 09:36:06.106 durabletask-worker INFO: f4e1926e-3721-478d-be8a-f5bebd1995da: Orchestration completed with status: COMPLETED
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== APP == Workflow completed! Result: Completed
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== APP == Purchase of item is Completed
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```
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### (Optional) Step 4: View in Zipkin
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If you have Zipkin configured for Dapr locally on your machine, you can view the workflow trace spans in the Zipkin web UI (typically at `http://localhost:9411/zipkin/`).
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<img src="/images/workflow-trace-spans-zipkin-python.png" width=900 style="padding-bottom:15px;">
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### What happened?
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When you ran `dapr run --app-id order-processor --resources-path ../../../components/ -- python3 app.py`:
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1. A unique order ID for the workflow is generated (in the above example, `f4e1926e-3721-478d-be8a-f5bebd1995da`) and the workflow is scheduled.
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1. The `NotifyActivity` workflow activity sends a notification saying an order for 10 cars has been received.
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1. The `ReserveInventoryActivity` workflow activity checks the inventory data, determines if you can supply the ordered item, and responds with the number of cars in stock.
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1. Your workflow starts and notifies you of its status.
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1. The `ProcessPaymentActivity` workflow activity begins processing payment for order `f4e1926e-3721-478d-be8a-f5bebd1995da` and confirms if successful.
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1. The `UpdateInventoryActivity` workflow activity updates the inventory with the current available cars after the order has been processed.
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1. The `NotifyActivity` workflow activity sends a notification saying that order `f4e1926e-3721-478d-be8a-f5bebd1995da` has completed.
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1. The workflow terminates as completed.
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#### `order-processor/app.py`
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In the application's program file:
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- The unique workflow order ID is generated
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- The workflow is scheduled
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- The workflow status is retrieved
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- The workflow and the workflow activities it invokes are registered
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```python
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class WorkflowConsoleApp:
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def main(self):
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# Register workflow and activities
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workflowRuntime = WorkflowRuntime(settings.DAPR_RUNTIME_HOST, settings.DAPR_GRPC_PORT)
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workflowRuntime.register_workflow(order_processing_workflow)
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workflowRuntime.register_activity(notify_activity)
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workflowRuntime.register_activity(requst_approval_activity)
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workflowRuntime.register_activity(verify_inventory_activity)
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workflowRuntime.register_activity(process_payment_activity)
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workflowRuntime.register_activity(update_inventory_activity)
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workflowRuntime.start()
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print("==========Begin the purchase of item:==========", flush=True)
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item_name = default_item_name
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order_quantity = 10
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total_cost = int(order_quantity) * baseInventory[item_name].per_item_cost
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order = OrderPayload(item_name=item_name, quantity=int(order_quantity), total_cost=total_cost)
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# Start Workflow
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print(f'Starting order workflow, purchasing {order_quantity} of {item_name}', flush=True)
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start_resp = daprClient.start_workflow(workflow_component=workflow_component,
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workflow_name=workflow_name,
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input=order)
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_id = start_resp.instance_id
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def prompt_for_approval(daprClient: DaprClient):
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daprClient.raise_workflow_event(instance_id=_id, workflow_component=workflow_component,
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event_name="manager_approval", event_data={'approval': True})
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approval_seeked = False
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start_time = datetime.now()
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while True:
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time_delta = datetime.now() - start_time
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state = daprClient.get_workflow(instance_id=_id, workflow_component=workflow_component)
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if not state:
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print("Workflow not found!") # not expected
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elif state.runtime_status == "Completed" or\
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state.runtime_status == "Failed" or\
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state.runtime_status == "Terminated":
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print(f'Workflow completed! Result: {state.runtime_status}', flush=True)
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break
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if time_delta.total_seconds() >= 10:
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state = daprClient.get_workflow(instance_id=_id, workflow_component=workflow_component)
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if total_cost > 50000 and (
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state.runtime_status != "Completed" or
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state.runtime_status != "Failed" or
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state.runtime_status != "Terminated"
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) and not approval_seeked:
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approval_seeked = True
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threading.Thread(target=prompt_for_approval(daprClient), daemon=True).start()
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print("Purchase of item is ", state.runtime_status, flush=True)
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def restock_inventory(self, daprClient: DaprClient, baseInventory):
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for key, item in baseInventory.items():
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print(f'item: {item}')
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item_str = f'{{"name": "{item.item_name}", "quantity": {item.quantity},\
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"per_item_cost": {item.per_item_cost}}}'
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daprClient.save_state("statestore-actors", key, item_str)
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if __name__ == '__main__':
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app = WorkflowConsoleApp()
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app.main()
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```
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#### `order-processor/workflow.py`
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In `workflow.py`, the workflow is defined as a class with all of its associated tasks (determined by workflow activities).
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```python
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def order_processing_workflow(ctx: DaprWorkflowContext, order_payload_str: OrderPayload):
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"""Defines the order processing workflow.
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When the order is received, the inventory is checked to see if there is enough inventory to
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fulfill the order. If there is enough inventory, the payment is processed and the inventory is
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updated. If there is not enough inventory, the order is rejected.
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If the total order is greater than $50,000, the order is sent to a manager for approval.
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"""
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order_id = ctx.instance_id
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order_payload=json.loads(order_payload_str)
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yield ctx.call_activity(notify_activity,
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input=Notification(message=('Received order ' +order_id+ ' for '
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+f'{order_payload["quantity"]}' +' ' +f'{order_payload["item_name"]}'
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+' at $'+f'{order_payload["total_cost"]}' +' !')))
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result = yield ctx.call_activity(verify_inventory_activity,
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input=InventoryRequest(request_id=order_id,
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item_name=order_payload["item_name"],
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quantity=order_payload["quantity"]))
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if not result.success:
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yield ctx.call_activity(notify_activity,
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input=Notification(message='Insufficient inventory for '
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+f'{order_payload["item_name"]}'+'!'))
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return OrderResult(processed=False)
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if order_payload["total_cost"] > 50000:
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yield ctx.call_activity(requst_approval_activity, input=order_payload)
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approval_task = ctx.wait_for_external_event("manager_approval")
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timeout_event = ctx.create_timer(timedelta(seconds=200))
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winner = yield when_any([approval_task, timeout_event])
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if winner == timeout_event:
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yield ctx.call_activity(notify_activity,
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input=Notification(message='Payment for order '+order_id
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+' has been cancelled due to timeout!'))
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return OrderResult(processed=False)
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approval_result = yield approval_task
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if approval_result["approval"]:
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yield ctx.call_activity(notify_activity, input=Notification(
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message=f'Payment for order {order_id} has been approved!'))
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else:
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yield ctx.call_activity(notify_activity, input=Notification(
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message=f'Payment for order {order_id} has been rejected!'))
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return OrderResult(processed=False)
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yield ctx.call_activity(process_payment_activity, input=PaymentRequest(
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request_id=order_id, item_being_purchased=order_payload["item_name"],
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amount=order_payload["total_cost"], quantity=order_payload["quantity"]))
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try:
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yield ctx.call_activity(update_inventory_activity,
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input=PaymentRequest(request_id=order_id,
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item_being_purchased=order_payload["item_name"],
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amount=order_payload["total_cost"],
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quantity=order_payload["quantity"]))
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except Exception:
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yield ctx.call_activity(notify_activity,
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input=Notification(message=f'Order {order_id} Failed!'))
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return OrderResult(processed=False)
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yield ctx.call_activity(notify_activity, input=Notification(
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message=f'Order {order_id} has completed!'))
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return OrderResult(processed=True)
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```
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{{% /codetab %}}
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