mirror of https://github.com/dapr/quickstarts.git
81 lines
2.4 KiB
Markdown
81 lines
2.4 KiB
Markdown
# Task Chaining Pattern
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This tutorial demonstrates how to chain multiple tasks together as a sequence in a workflow, where the output of one task is used as the input for the next one. For more information about the task chaining pattern see the [Dapr docs](https://docs.dapr.io/developing-applications/building-blocks/workflow/workflow-patterns/#task-chaining).
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## Inspect the code
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Open the `chaining_workflow.py` file in the `tutorials/workflow/python/task-chaining/task_chaining` folder. This file contains the definition for the workflow.
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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[activity1]
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A2[activity2]
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A3[activity3]
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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 --> A3
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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/python/task-chaining/task_chaining` folder.
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2. Install the dependencies using pip:
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```bash
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pip3 install -r requirements.txt
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```
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3. Navigate back one level to the `task-chaining` folder and 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 "chaining"'
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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 [`chaining.http`](./chaining.http) file to start the workflow, or use this cURL command:
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```bash
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curl -i --request POST http://localhost:5255/start
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```
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The input for the workflow is a string with the value `This`. The expected app logs are as follows:
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```text
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== APP - chaining == activity1: Received input: This.
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== APP - chaining == activity2: Received input: This is.
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== APP - chaining == activity3: Received input: This is task.
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```
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5. Use the GET request in the [`chaining.http`](./chaining.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:3555/v1.0/workflows/dapr/<INSTANCEID>
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```
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Where `<INSTANCEID>` is the workflow instance ID you received in the `instance_id` property in the previous step.
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The expected serialized output of the workflow is:
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```txt
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"\"This is task chaining\""
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```
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6. Stop the Dapr Multi-App run process by pressing `Ctrl+C`.
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