Tracecat will always support unlimited workflows. We recommend breaking up your workflows into smaller, reusable workflows whenever possible.

By the end of this tutorial, you’ll learn how to:

  • Call a workflow from another workflow
  • Give a workflow a human-readable alias
  • Use trigger_input to pass data into a child workflow
  • Use Output Schema to define the data returned from a child workflow

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Execute child workflow

Use the core.workflow.execute action to call a workflow from another workflow. You can call a workflow by workflow_alias (recommended) or by workflow_id.

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Alias

Give your workflows an alias to call them by a human-readable name, in core.workflow.execute, as opposed to the workflow ID.

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Trigger Inputs

In the workflow triggers tutorial, we learned how to pass data into workflows via webhook payloads. Passing data into child workflows works the same way.

To pass data into a child workflow, specify trigger_inputs in the core.workflow.execute action’s inputs. trigger_inputs takes a JSON-serializable object exactly like webhook payloads.

For example, the core.workflow.execute action inputs might be configured as:

workflow_alias: get_weather
trigger_inputs:
  latitude: 37.773972
  longitude: -122.431297

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Output Schema

We recommend users define an Output Schema for every workflow.

You can use all core expression contexts: e.g. ACTIONS, TRIGGER, FN within the Output Schema field.

By default, workflows return a JSON object that contains the entire workflow context. The workflow context includes the inputs and outputs of every action from the workflow run.

You almost never want to return the entire workflow context as the output of a workflow. The Output Schema field under the Schemas tab in workflow settings allows you to define the data returned from a workflow.

The data returned from a workflow can be any JSON-serializable value. For example, the Output Schema field can be configured as a nested JSON object:

temperature: ${{ ACTIONS.http_request.result.data.current.temperature_2m }}
coordinates:
  lat: ${{ TRIGGER.latitude }}
  long: ${{ TRIGGER.longitude }}
timestamp: ${{ ACTIONS.http_request.result.data.time }}

or even a single value:

${{ ACTIONS.http_request.result.data.current.temperature_2m }}

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Tutorial

This tutorial assumes you’ve already completed the Quickstart tutorial.

In the quickstart tutorial, we built a workflow called Get weather that calls a weather API for the temperature. Let’s build another workflow that calls the Get weather workflow for three different locations (New York, London, and Tokyo).

1

Parameterize child workflow

We currently hardcode the coordinates in the Get weather workflow. Let’s change this so that we can pass in coordinates from the webhook trigger into the HTTP Request action.

url: https://api.open-meteo.com/v1/forecast
method: GET
params:
  latitude: ${{ TRIGGER.latitude }}  # Was 37.773972
  longitude: ${{ TRIGGER.longitude }}  # Was -122.431297
  current: temperature_2m

2

Create parent workflow

Create a new workflow. Add three core.workflow.execute actions to the workflow, one for each location. Configure each core.workflow.execute action to call the Get weather workflow (with alias get_weather) with the appropriate coordinates.

3

Run parent workflow

Run the parent workflow. Notice in Action result that the child workflow returns the entire workflow context as the output of the parent workflow. In this next step, we’ll add an Output Schema to the Get weather child workflow to return only the temperature.

4

Add output schema

Add an Output Schema to the Get weather workflow. Configure the Output Schema to return only the temperature. Save the workflow.

${{ ACTIONS.http_request.result.data.current.temperature_2m }}

5

Rerun parent workflow

Run the parent workflow again. Notice in Action result that the child workflow now returns only the temperature.

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What next?

Learn the recommended way to process lists of complex data, such as alerts or threat feeds, using loops and child workflows in the explode-implode tutorial.

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