---
title: 'CatBus: logging'
subtitle: easy low-configuration logging
date: 2020-02-20
---
{% extends 'templates/base.html' %}
{% block body %}
	<nav>
		<a href='/catbus'>&gt; catbus home</a>
	</nav>
	<header>
		<h1>{{ title }}</h1>
		<p>{{ subtitle }}</p>
	</header>
	<article>
{% markdown %}
Using the MQTT bus as a unified system with a unified semantic naming scheme means that I can also implement logging without the need for much configuration.

Following the above scheme, we can automatically scrape all devices named `*-sensor` into Prometheus metrics:

```
$control{zone=$zone,device=$device} = $value
```

For example,

```
temperature_celsius{zone=bedroom,device=window-sensor} = 17
```

Likewise, we can export enums as:

```
home/zone/device/control_enum:
    foo

home/zone/device/control_enum/values:
    bar
    foo

control{zone=,device=,value=bar} = 0
control{zone=,device=,value=foo} = 1
```
{% endmarkdown %}
	</article>
{% endblock %}