mirror of https://github.com/dapr/docs.git
Merge branch 'v1.11' into 1-11_ENDGAME
This commit is contained in:
commit
93e2616ef2
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@ -31,6 +31,7 @@ metadata:
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name: lockstore
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spec:
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type: lock.redis
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version: v1
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metadata:
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- name: redisHost
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value: localhost:6379
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@ -25,9 +25,10 @@ While the pattern is simple, there are many complexities hidden in the implement
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Dapr Workflow solves these complexities by allowing you to implement the task chaining pattern concisely as a simple function in the programming language of your choice, as shown in the following example.
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{{< tabs ".NET" >}}
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{{< tabs ".NET" Python >}}
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{{% codetab %}}
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<!--dotnet-->
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```csharp
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// Expotential backoff retry policy that survives long outages
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@ -45,7 +46,6 @@ try
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var result1 = await context.CallActivityAsync<string>("Step1", wfInput, retryOptions);
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var result2 = await context.CallActivityAsync<byte[]>("Step2", result1, retryOptions);
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var result3 = await context.CallActivityAsync<long[]>("Step3", result2, retryOptions);
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var result4 = await context.CallActivityAsync<Guid[]>("Step4", result3, retryOptions);
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return string.Join(", ", result4);
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}
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catch (TaskFailedException) // Task failures are surfaced as TaskFailedException
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@ -56,14 +56,61 @@ catch (TaskFailedException) // Task failures are surfaced as TaskFailedException
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}
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```
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{{% alert title="Note" color="primary" %}}
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In the example above, `"Step1"`, `"Step2"`, `"Step3"`, and `"MyCompensation"` represent workflow activities, which are functions in your code that actually implement the steps of the workflow. For brevity, these activity implementations are left out of this example.
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{{% /alert %}}
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{{% /codetab %}}
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{{% codetab %}}
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<!--python-->
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```python
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import dapr.ext.workflow as wf
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def task_chain_workflow(ctx: wf.DaprWorkflowContext, wf_input: int):
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try:
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result1 = yield ctx.call_activity(step1, input=wf_input)
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result2 = yield ctx.call_activity(step2, input=result1)
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result3 = yield ctx.call_activity(step3, input=result2)
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except Exception as e:
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yield ctx.call_activity(error_handler, input=str(e))
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raise
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return [result1, result2, result3]
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def step1(ctx, activity_input):
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print(f'Step 1: Received input: {activity_input}.')
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# Do some work
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return activity_input + 1
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def step2(ctx, activity_input):
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print(f'Step 2: Received input: {activity_input}.')
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# Do some work
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return activity_input * 2
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def step3(ctx, activity_input):
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print(f'Step 3: Received input: {activity_input}.')
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# Do some work
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return activity_input ^ 2
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def error_handler(ctx, error):
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print(f'Executing error handler: {error}.')
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# Do some compensating work
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```
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{{% alert title="Note" color="primary" %}}
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Workflow retry policies will be available in a future version of the Python SDK.
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{{% /alert %}}
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{{% /codetab %}}
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{{< /tabs >}}
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{{% alert title="Note" color="primary" %}}
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In the example above, `"Step1"`, `"Step2"`, `"MyCompensation"`, etc. represent workflow activities, which are functions in your code that actually implement the steps of the workflow. For brevity, these activity implementations are left out of this example.
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{{% /alert %}}
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As you can see, the workflow is expressed as a simple series of statements in the programming language of your choice. This allows any engineer in the organization to quickly understand the end-to-end flow without necessarily needing to understand the end-to-end system architecture.
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Behind the scenes, the Dapr Workflow runtime:
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Dapr Workflows provides a way to express the fan-out/fan-in pattern as a simple function, as shown in the following example:
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{{< tabs ".NET" >}}
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{{< tabs ".NET" Python >}}
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{{% codetab %}}
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<!--dotnet-->
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```csharp
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// Get a list of N work items to process in parallel.
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{{% /codetab %}}
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{{% codetab %}}
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<!--python-->
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```python
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import time
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from typing import List
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import dapr.ext.workflow as wf
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def batch_processing_workflow(ctx: wf.DaprWorkflowContext, wf_input: int):
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# get a batch of N work items to process in parallel
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work_batch = yield ctx.call_activity(get_work_batch, input=wf_input)
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# schedule N parallel tasks to process the work items and wait for all to complete
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parallel_tasks = [ctx.call_activity(process_work_item, input=work_item) for work_item in work_batch]
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outputs = yield wf.when_all(parallel_tasks)
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# aggregate the results and send them to another activity
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total = sum(outputs)
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yield ctx.call_activity(process_results, input=total)
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def get_work_batch(ctx, batch_size: int) -> List[int]:
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return [i + 1 for i in range(batch_size)]
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def process_work_item(ctx, work_item: int) -> int:
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print(f'Processing work item: {work_item}.')
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time.sleep(5)
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result = work_item * 2
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print(f'Work item {work_item} processed. Result: {result}.')
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return result
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def process_results(ctx, final_result: int):
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print(f'Final result: {final_result}.')
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```
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{{% /codetab %}}
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{{< /tabs >}}
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The key takeaways from this example are:
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@ -214,9 +302,10 @@ Depending on the business needs, there may be a single monitor or there may be m
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Dapr Workflow supports this pattern natively by allowing you to implement _eternal workflows_. Rather than writing infinite while-loops ([which is an anti-pattern]({{< ref "workflow-features-concepts.md#infinite-loops-and-eternal-workflows" >}})), Dapr Workflow exposes a _continue-as-new_ API that workflow authors can use to restart a workflow function from the beginning with a new input.
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{{< tabs ".NET" >}}
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{{< tabs ".NET" Python >}}
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{{% codetab %}}
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<!--dotnet-->
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```csharp
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public override async Task<object> RunAsync(WorkflowContext context, MyEntityState myEntityState)
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{{% /codetab %}}
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{{% codetab %}}
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<!--python-->
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```python
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from dataclasses import dataclass
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from datetime import timedelta
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import random
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import dapr.ext.workflow as wf
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@dataclass
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class JobStatus:
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job_id: str
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is_healthy: bool
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def status_monitor_workflow(ctx: wf.DaprWorkflowContext, job: JobStatus):
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# poll a status endpoint associated with this job
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status = yield ctx.call_activity(check_status, input=job)
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if not ctx.is_replaying:
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print(f"Job '{job.job_id}' is {status}.")
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if status == "healthy":
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job.is_healthy = True
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next_sleep_interval = 60 # check less frequently when healthy
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else:
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if job.is_healthy:
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job.is_healthy = False
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ctx.call_activity(send_alert, input=f"Job '{job.job_id}' is unhealthy!")
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next_sleep_interval = 5 # check more frequently when unhealthy
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yield ctx.create_timer(fire_at=ctx.current_utc_datetime + timedelta(seconds=next_sleep_interval))
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# restart from the beginning with a new JobStatus input
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ctx.continue_as_new(job)
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def check_status(ctx, _) -> str:
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return random.choice(["healthy", "unhealthy"])
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def send_alert(ctx, message: str):
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print(f'*** Alert: {message}')
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```
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{{% /codetab %}}
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{{< /tabs >}}
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A workflow implementing the monitor pattern can loop forever or it can terminate itself gracefully by not calling _continue-as-new_.
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The following example code shows how this pattern can be implemented using Dapr Workflow.
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{{< tabs ".NET" >}}
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{{< tabs ".NET" Python >}}
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{{% codetab %}}
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<!--dotnet-->
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```csharp
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public override async Task<OrderResult> RunAsync(WorkflowContext context, OrderPayload order)
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{{% /codetab %}}
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{{% codetab %}}
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<!--python-->
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```python
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from dataclasses import dataclass
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from datetime import timedelta
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import dapr.ext.workflow as wf
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@dataclass
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class Order:
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cost: float
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product: str
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quantity: int
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def __str__(self):
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return f'{self.product} ({self.quantity})'
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@dataclass
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class Approval:
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approver: str
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@staticmethod
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def from_dict(dict):
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return Approval(**dict)
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def purchase_order_workflow(ctx: wf.DaprWorkflowContext, order: Order):
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# Orders under $1000 are auto-approved
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if order.cost < 1000:
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return "Auto-approved"
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# Orders of $1000 or more require manager approval
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yield ctx.call_activity(send_approval_request, input=order)
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# Approvals must be received within 24 hours or they will be canceled.
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approval_event = ctx.wait_for_external_event("approval_received")
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timeout_event = ctx.create_timer(timedelta(hours=24))
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winner = yield wf.when_any([approval_event, timeout_event])
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if winner == timeout_event:
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return "Cancelled"
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# The order was approved
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yield ctx.call_activity(place_order, input=order)
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approval_details = Approval.from_dict(approval_event.get_result())
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return f"Approved by '{approval_details.approver}'"
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def send_approval_request(_, order: Order) -> None:
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print(f'*** Sending approval request for order: {order}')
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def place_order(_, order: Order) -> None:
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print(f'*** Placing order: {order}')
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```
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{{% /codetab %}}
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{{< /tabs >}}
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The code that delivers the event to resume the workflow execution is external to the workflow. Workflow events can be delivered to a waiting workflow instance using the [raise event]({{< ref "howto-manage-workflow.md#raise-an-event" >}}) workflow management API, as shown in the following example:
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{{< tabs ".NET" >}}
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{{< tabs ".NET" Python >}}
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{{% codetab %}}
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<!--dotnet-->
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```csharp
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// Raise the workflow event to the waiting workflow
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@ -350,6 +547,23 @@ await daprClient.RaiseWorkflowEventAsync(
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{{% /codetab %}}
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{{% codetab %}}
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<!--python-->
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```python
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from dapr.clients import DaprClient
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from dataclasses import asdict
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with DaprClient() as d:
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d.raise_workflow_event(
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instance_id=instance_id,
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workflow_component="dapr",
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event_name="approval_received",
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event_data=asdict(Approval("Jane Doe")))
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```
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{{% /codetab %}}
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{{< /tabs >}}
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External events don't have to be directly triggered by humans. They can also be triggered by other systems. For example, a workflow may need to pause and wait for a payment to be received. In this case, a payment system might publish an event to a pub/sub topic on receipt of a payment, and a listener on that topic can raise an event to the workflow using the raise event workflow API.
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@ -1 +1 @@
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Subproject commit 11145914a5fddd1ada06b6a3b938c27b401f7025
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Subproject commit 1e3b6eb859be175e12808c0ff345f40398f209d6
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