mirror of https://github.com/dapr/quickstarts.git
96 lines
3.3 KiB
Markdown
96 lines
3.3 KiB
Markdown
# Resiliency & Compensation
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This tutorial demonstrates how to improve resiliency when activities are executed and how to include compensation actions when activities return an error. For more on workflow resiliency read the [Dapr docs](https://docs.dapr.io/developing-applications/building-blocks/workflow/workflow-features-concepts/#retry-policies).
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## Inspect the code
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Open the `ResiliencyAndCompensationWorkflow.cs` file in the `tutorials/workflow/csharp/resiliency-and-compensation/ResiliencyAndCompensation` folder. This file contains the definition for the workflow. This workflow implements an activity retry policy on all the associated activities and compensating logic if an activity throws an exception.
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```mermaid
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graph LR
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SW((Start
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Workflow))
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A1[MinusOne]
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A2[Division]
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EX{Division
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Exception?}
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A3[PlusOne]
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EW((End
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Workflow))
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SW --> A1
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A1 --> A2
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A2 --> EX
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EX -- yes --> A3
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EX -- no --> EW
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A3 --> EW
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```
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## Run the tutorial
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1. Use a terminal to navigate to the `tutorials/workflow/csharp/resiliency-and-compensation` folder.
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2. Build the project using the .NET CLI.
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```bash
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dotnet build ./ResiliencyAndCompensation/
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```
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3. Use the Dapr CLI to run the Dapr Multi-App run file
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<!-- STEP
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name: Run multi app run template
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expected_stdout_lines:
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- 'Started Dapr with app id "resiliency"'
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expected_stderr_lines:
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working_dir: .
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output_match_mode: substring
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background: true
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sleep: 15
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timeout_seconds: 30
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-->
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```bash
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dapr run -f .
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```
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<!-- END_STEP -->
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4. Use the POST request in the [`resiliency-compensation.http`](./resiliency-compensation.http) file to start the workflow with a workflow input value of `1`, or use this cURL command:
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```bash
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curl -i --request POST \
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--url http://localhost:5264/start/1
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```
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When the workflow input is `1`, the `MinusOne` activity will subtract `1` resulting in a `0`. This value is passed to the `Division` activity, which will throw an error because the divisor is `0`. The `Division` activity will be retried three times but all will fail the same way as the divisor has not changed. Finally the compensation action `PlusOne` will be executed, increasing the value back to `1` before returning the result.
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The app logs should output the following:
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```txt
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== APP - resiliency == MinusOne: Received input: 1.
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== APP - resiliency == Division: Received divisor: 0.
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== APP - resiliency == Division: Received divisor: 0.
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== APP - resiliency == Division: Received divisor: 0.
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== APP - resiliency == PlusOne: Received input: 0.
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```
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5. Use the GET request in the [`resiliency-compensation.http`](./resiliency-compensation.http) file to get the status of the workflow, or use this cURL command:
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```bash
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curl --request GET --url http://localhost:3564/v1.0/workflows/dapr/<INSTANCEID>
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```
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Where `<INSTANCEID>` is the workflow instance ID you received in the `Location` header in the previous step.
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```
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Since `1` is used as the input, the expected serialized output of the workflow is:
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```txt
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"1"
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```
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The expected serialized custom status field of the workflow output is:
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```txt
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"\"Compensated MinusOne activity with PlusOne activity.\""
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```
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6. Stop the Dapr Multi-App run process by pressing `Ctrl+C`.
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