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HTTP Call

Fetch data from an external HTTP API and store the response in workflow state.

What you will learn​

  • How to make an HTTP GET request from a workflow using call: http
  • How to capture and shape the HTTP response body
  • How to pass dynamic values to an endpoint using runtime expressions

Workflow​

workflow.yaml
document:
  dsl: 1.0.0
  namespace: zigflow
  name: fetch-user
  version: 0.0.1
do:
  - getUser:
      call: http
      output:
        as:
          user: ${ . }
      with:
        method: get
        endpoint: https://jsonplaceholder.typicode.com/users/1

Explanation​

The call: http task runs as a Temporal activity. It makes the request, then returns the response body as the task output. output.as maps that body into { "user": ... }.

Retry behaviour. Failed HTTP calls (non-2xx responses) are retried using the workflow's retry policy. Wrap the call in a try task to intercept specific errors.

Passing dynamic values to the endpoint​

Use a runtime expression in endpoint:

with:
  method: get
  endpoint: >-
    ${ "https://jsonplaceholder.typicode.com/users/"
    + ($input.userId | tostring) }

The $input variable holds the data passed when the workflow was triggered.

How to run​

  1. Start a Temporal development server:

    temporal server start-dev

  2. Start the worker:

    zigflow run -f workflow.yaml

  3. Trigger the workflow:

    temporal workflow start \
      --type fetch-user \
      --task-queue zigflow \
      --workflow-id fetch-1

  4. View the result:

    temporal workflow show --workflow-id fetch-1

Expected output​

{
  "user": {
    "id": 1,
    "name": "Leanne Graham"
  }
}

Common mistakes​

The call succeeds locally but fails in production. Ensure the Zigflow worker process has network access to the target endpoint.

Non-2xx responses fail the workflow. HTTP errors raise by default. To recover, wrap the call in a try task. See Error Handling.