From 28a5b3a6da98efb9a70b9b190e85c6197bb8712d Mon Sep 17 00:00:00 2001 From: Faithful Adeda <93828448+Adematics@users.noreply.github.com> Date: Thu, 26 Sep 2024 22:54:52 +0100 Subject: [PATCH] feat(docs): updated Conditional branching with Switch task (#1782) * feat(docs): updated Conditional branching with Switch task * Update conditional-branching.md * Update content/docs/15.how-to-guides/conditional-branching.md --------- Co-authored-by: Anna Geller --- .../15.how-to-guides/conditional-branching.md | 96 ++++++++++++++++++- 1 file changed, 95 insertions(+), 1 deletion(-) diff --git a/content/docs/15.how-to-guides/conditional-branching.md b/content/docs/15.how-to-guides/conditional-branching.md index dba2dcc340..3f607d9f55 100644 --- a/content/docs/15.how-to-guides/conditional-branching.md +++ b/content/docs/15.how-to-guides/conditional-branching.md @@ -9,7 +9,20 @@ topics: How to use the Switch task to branch the flow based on a value. -Depending on the value passed as input, the will flow branch to different tasks. If there is no matching value, Kestra will use the `defaults` branch. +Conditional branching is a process in which the execution of a task is directed along different paths based on specific values. In a flow, it allows for decision-making, where different tasks are executed depending on the value provided. + +In this guide, you'll learn how to use Kestra's `Switch` task to control your flow based on a value passed. Depending on the value passed in the `Switch` task, the flow will branch to different task `cases` to execute a specific task. If there is no matching value, Kestra will use the `defaults` branch. + +## Prerequisites + +Before you begin: + +- Deploy [Kestra](https://kestra.io/docs/installation) in your preferred development environment. +- Ensure you have a [basic understanding of how to run Kestra flows.](https://kestra.io/docs/getting-started/tutorial) + +## Example 1: Conditional Branching with Input Strings + +This flow template serves as an introductory example to understand how the `Switch` task works within Kestra. The flow dynamically branches to different tasks depending on the input string. To see the flow in action, define the `switch` flow as shown below: ```yaml id: switch @@ -59,3 +72,84 @@ outputs: type: STRING value: "{{ outputs.first ?? outputs.second1 ?? outputs.third1 ?? outputs.default }}" ``` + +Save and execute the `switch` flow. + +You can input `FIRST`, `SECOND`, `THIRD`, or any other input string to see the flow in action. The above flow when executed checks a sequence of tasks based on the input string you provide. + +Within the flow: + +- `inputs`: Takes a string input to determine which case to execute. +- `tasks`: Handles the input string with the following values: + - `id: parent-seq`: Uses the `Switch` task to evaluate the input string and execute a case that matches the input string with the following cases: + - `FIRST`: Executes task `first`, returning its ID and start time. + - `SECOND`: Executes two tasks (`second1` and `second2`), both returning their task ID and start time. + - `THIRD`: Runs a sequence of tasks where the `failed` task triggers an error and executes the `error1` task, which logs an error message. + - `defaults`: If the input doesn't match any cases, it runs the `default` task and logs the task ID and start time. +- `outputs`: Extracts and logs the output from one of the executed tasks (`first`, `second1`, `third1`, or `default`). + +## Example 2: Conditional branching with Kestra’s website status + +To see the `Switch` task in action without an input string, we’ll create a flow to make a decision based on the status of an HTTP request to Kestra’s website. To follow along and implement this, define the `kestra-http-switch` flow as described below: + +```yaml +id: kestra-http-switch +namespace: company.team + +tasks: + - id: check_kestra_site + type: io.kestra.plugin.scripts.python.Script + outputFiles: + - site_status.txt + script: | + import requests + response = requests.head("https://kestra.io") + with open('site_status.txt', 'w') as f: + f.write(str(response.status_code)) + + - id: decide_site_status + type: io.kestra.plugin.core.flow.Switch + value: "{{ read(outputs.check_kestra_site.outputFiles['site_status.txt']) }}" + cases: + "200": + - id: log-site-up + type: io.kestra.plugin.core.log.Log + message: "Kestra website is up and running. Status: 200" + + "404": + - id: log-site-down + type: io.kestra.plugin.core.log.Log + message: "Kestra website not found. Status: 404" + + defaults: + - id: unknown-status + type: io.kestra.plugin.core.log.Log + message: "Received unexpected status code: {{ read(outputs.check_kestra_site.outputFiles['site_status.txt']) }}" + +outputs: + - id: status-output + type: STRING + value: "{{ outputs.log-site-up ?? outputs.log-site-down ?? outputs.unknown-status }}" + +``` + +Save and execute the `kestra-http-switch` flow. + +The above flow when executed checks the status of Kestra’s website and logs a message depending on the response code returned. + +Within the flow: + +- `tasks`: Handles the status check of the Kestra website with the following tasks: + - `id: check_kestra_site`: Executes a Python script to send a HEAD request to the Kestra website and writes the HTTP status code to a `site_status.txt` file. + - `id: decide_site_status`: Utilizes the `Switch` task to evaluate the HTTP status code from the `check_kestra_site` task: + - If the status code is `"200"`, it logs a message indicating the site is up. + - If the status code is `"404"`, it logs a message indicating the site is not found. + - If an unexpected status code is received, it falls back to the `defaults` branch with a message indicating unknown status. +- `outputs`: Extracts and logs the output status message based on the logs generated from the `Switch` task. + +## Next Steps + +You have implemented conditional branching with the `Switch` task using the `switch` flow to check your input strings and `kestra-http-switch` flow to check Kestra’s website status. The `Switch` task can further be implemented in various use cases to support your flows. Further resources about the `Switch` task: + +- [Kestra’s official Switch task plugin documentation](https://kestra.io/plugins/core/tasks/flow/io.kestra.plugin.core.flow.switch) +- [Kestra’s Blueprint Switch task use cases](https://kestra.io/blueprints?page=1&size=24&q=switch)