Edge App Academy · 4 / 5

Add a scheduled health entry point

Keep message handling separate from a five-minute scheduled check.

YOUR TASK

Make this happen

3 steps

Add a separate health handler returning { alive = true } and a CRON trigger every five minutes (*/5 * * * *). Keep MQTT reception.
Keep the working capabilities from the previous lesson and connect the new pieces to the same solution.
Check the complete solution, then inspect any unmet requirements.

THE IDEA BEHIND IT

What this step adds

Add a separate health handler returning { alive = true } and a CRON trigger every five minutes (*/5 * * * *). Keep MQTT reception.

Files to work in

main.cococo, health.cococo. Other files are the working baseline. New files include named resource skeletons and TODO guidance. Complete their fields and connect them using the objectives, schema completion and reference guide.

Independent entry points

The CRON trigger invokes health; MQTT invokes receive. A handler is reusable but each event source supplies its own parameters.

Health is a narrow claim

Returning alive confirms only that the handler ran when deployed. It does not establish broker connectivity, machine health or successful delivery. Those require real controller observations.

Checks validate authored native models and lesson connections. No controller, MQTT broker, protocol request, handler or installation is executed.

Files to change: main.cococo, health.cococo

What you’re building: Build a portable plant-state listener whose broker settings and secrets belong to each controller installation.

This step starts with the earlier solution and one new challenge. Each lesson keeps its own draft.

Read the starter files

main.cococo

edge_app_document "main" {
  format = "1"
  handle = "plant-monitor"
  name = "Plant monitor"
  handlers = [edge_app_handler.receive]
  mqttBrokers = [edge_app_mqtt_broker.plant]
  configSchema = {
    type = "object"
    properties = {
      MQTT_URL = {
        type = "string"
      }
      MQTT_USERNAME = {
        type = "string"
      }
      MQTT_PASSWORD = {
        type = "string"
        writeOnly = true
      }
      MQTT_CA = {
        type = "string"
        writeOnly = true
      }
    }
    required = ["MQTT_URL", "MQTT_USERNAME", "MQTT_PASSWORD", "MQTT_CA"]
    additionalProperties = false
  }
}

handlers.cococo

edge_app_handler "receive" {
  name = "receive"
  source = file("scripts/receive.lua")
}

scripts/receive.lua

bridge.log.info(params.topic)
return params.payload

broker.cococo

edge_app_mqtt_broker "plant" {
  name = "plant"
  url = "$${config:MQTT_URL}"
  qos = 1
  subscriptions = [edge_app_mqtt_subscription.state]
  username = "$${config:MQTT_USERNAME}"
  password = {
    config = "MQTT_PASSWORD"
  }
  tls = {
    caCertPem = {
      config = "MQTT_CA"
    }
  }
}

subscription.cococo

edge_app_mqtt_subscription "state" {
  topic = "plant/+/state"
  handler = "receive"
}

health.cococo

edge_app_handler "health" {
  name = "health"
  # TODO: add source — see the task above.
}

Supplied supporting files

Reference: edge-apps · getting-started edge-apps · definitions edge-apps · scripts-triggers edge-apps · mqtt-opcua edge-apps · industrial edge-apps · exec-http edge-apps · diagnostics edge-apps · reference