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# Monitor mqtt services

The whole system relies on MQTT to communicate with different services, camera object_detection and so on. As these services are sensitive, we need to make sure everything works as expected. Here is a few example that we want to catch:

  • the core turn on the alarm but the service object_detection does not turn on. Basically the alarm won't work in that case.
  • same for the opposite, the resident will trigger the alarm if it does not turn off properly.
  • the object_detection disconnects but the alarm status (database) says the alarm is running.

Even if the code is well tested, even if we use QOS 1 or 2, we want to make sure everything works as exepected at run time because these services are sensitive, they protect your home, your places...

Information

As of today we use only mqtt to communicate with our services. In the future we might use something else, http, gprc... All of ours "checks" would still be valid, independantly of the protocol.

# Verify connect status

When a service connects/disconnects it sends a message to inform the core. If the status is registered in database, we are able to verify either or not the recieved status is corresponding to the status in database. If not, something is wrong.

You can do it by using the OnConnectedVerifyStatusHandler (opens new window) for your on connected handler.

# Verify status afer it changed

When the core change the status of a service, we might want to verify either or not the service actually connected or disconnected after a bit of time.

  1. Use the OnConnectedHandlerLog (opens new window) for the service. It will logs every connect/disconnect event.
  2. Call the function verify_services_status when you inform the new status to the service.

# Pings

Not generic

For now it is not implemented to be generic. That means it is not possible to use this feature for something else than object_detection service.

We will in the future.

The core has a simple mechanism of ping.

We use pings to make sure the object_detection service processes frames frequently for a given camera. So it makes sure everything is working, the camera send frames and object detection receives it to process.

The object detection service needs to send at a fixed interval of time a mqtt message which we call ping.

Side note, it does not have any relation with mqtt ping mechanism. It's totally different and does not serve the same purpose.

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