I've built an API which generates some content that is consumed by other devices. Since this operation is somewhat long-running (~25 seconds) and since devices don't require the freshest content, I wanted to have an automated job that calls the API every 20 minutes.

CRON would be the obvious choice, but as I'm running Home Assistant in my network, I looked at automations as a way to issue these regular HTTP calls.

Requirements

1. Repeated schedule - every 20 minutes.
2. Call an HTTP endpoint using GET with parameters.
3. Make those parameters configurable in the automation - for different types of devices.

Solution

First, I went to configuration.yaml and created new rest_command.

rest_command:
  refresh_paper:
    url: "http://my-ip-address/api/dashboard?force=true&type={{ type }}"
    method: GET

Then I had to restart HA in order for the new service to show up (simply reloading the configuration wasn't enough).

Finally, I went to Automations and created a new automation.

• Trigger is Time pattern. Hours and Seconds are empty, but Minutes I set to /20 (which means every 20-portion of an hour, i.e. 0, 20, 40, 0, 20, etc.).
• Actions are individual HTTP calls, for my case I have multiple that should differ by the type parameter. So for each of them:
  • Action type is Call service.
  • Service is RESTful command: refresh_paper.
  • Then go to Edit in YAML and add the data portion, which contains the parameter (type).

service: rest_command.refresh_paper
data:
  type: homeassistant
alias: Call API for "homeassistant"

This results in Home Assistant calling my API for each type of device every 20 minutes.