homebridge-prometheus-exporter/README.md

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<img src="https://github.com/homebridge/branding/raw/master/logos/homebridge-wordmark-logo-vertical.png" width="150">

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# Homebridge Prometheus Exporter

> What if we could store homebridge metrics in Prometheus

*homebridge-prometheus-exporter* is a plugin for *homebridge* that provides a metrics endpoint for *Prometheus* to scrape.
Once the metrics are in *Prometheus*, they can be consumed and presented in various ways. One can use *Prometheus
Alerting Rules* to trigger actions on certain thresholds or *Grafana* to build informative graphs or alerts.

![A Grafana timeseries showing wattage and voltage of two home appliances on a timeseries chart](https://user-images.githubusercontent.com/79707/200554468-940da6fb-b1c8-4b2e-bd76-f5e208bf72a3.png)


## Installing

### Install the plugin

Run this command to install the plugin as a global *nodejs* module:

```shell
npm install -g homebridge-prometheus-exporter
```

### Configure *homebridge*

Edit the *homebridge* `config.json` to load the plugin:
```json lines
{
    // …
    "platforms": [
    {
      "platform": "PrometheusExporter",
      "pin": "123-12-123",
    },
    // …
  ]
}
```

### Customize *homebridge* startup

For *homebridge-prometheus-exporter* to work, *homebridge* has to run in "insecure mode". This means that any user who
has access to your network can control your *homebridge* devices. This is usually not a big problem but it is still
something you should consciously decide. *homebridge-config-ui-x*
[requires running in insecure mode](https://github.com/oznu/homebridge-config-ui-x/wiki/Enabling-Accessory-Control)
if you want to control your devices from *homebridge-config-ui-x*.

To enable "insecure mode", edit the startup script for *homebridge* and add `--insecure` or `-I`. Assuming you run
systemd, the proper way to override the config would be to use *systemd’s* drop-in mechanism.

Create `/etc/systemd/system/homebridge.service.d` folder:
```shell
mkdir /etc/systemd/system/homebridge.service.d
```
Write this drop-in configuration file to /etc/systemd/system/homebridge.service.d/insecure.conf:
```ini
[Service]
ExecStart=
ExecStart=/usr/lib/node_modules/homebridge/bin/homebridge --insecure
```

The first and empty `ExecStart` tells *systemd* to forget about the `ExecStart` from the original service definition
and the second `ExecStart` declares the new file. Run `systemctl daemon-reload` to refresh *systemd’s* unit database
and then run `systemd-delta --type=extended` to check if the drop-in worked as expected.

You should see something like this in the output:

```text
…
[EXTENDED]   /lib/systemd/system/homebridge.service → /etc/systemd/system/homebridge.service.d/insecure.conf
…
```

If you are not using *systemd*, first of all, you absolutely should but second of all you will likely have some sort
of env file, e.g. `/etc/defaults/homebridge` to customize the *homebridge* start command. Restart *homebridge* using
`systemctl restart homebridge`.

Test that the metrics endpoint is available by accesing `http://homebridge-host:36123/metrics`. You should see a
response similar to this:

```text
# TYPE homebridge_air_purifier_active gauge
homebridge_air_purifier_active{name="…",…} 0 1667914208196
# TYPE homebridge_air_purifier_current_air_purifier_state gauge
homebridge_air_purifier_current_air_purifier_state{name="…",…} 0 1667914208196
```

### Configuring *Prometheus*

With *homebridge-prometheus-exporter* up and running, it is now time to configure *Prometheus* to scrape the config
endpoint. Go to your prometheus host and edit `/etc/prometheus/prometheus.yml` and add the following scrape config:

```yml

scrape_configs:
  - job_name: homebridge-exporter
    static_configs:
    - targets:
      - homebridge-host:36123
```

Once *Prometheus* is restarted, metrics with the `homebridge_` prefix should start to be ingested.

### Customize *homebridge-prometheus-exporter*

*homebridge-prometheus-exporter* offers a few advanced settings to customize its behavior.

```json lines
{
  // …
  "platforms": [
    {
      "platform": "PrometheusExporter",
      // Homebridge PIN for service authentication. String of digits, format XXX-XX-XXX. Required
      "pin": string,

      // Toggle debug mode. Run homebridge with -D if you want to see the debug output. Default: false
      "debug": boolean,

      // Prefix for all metrics. Default: "homebridge"
      "prefix": string,

      // TCP port where the Prometheus metrics server listens. Default: 36123
      "port": number,

      // How frequently the services should be rediscovered (in seconds). Default: 60
      "refresh_interval": number,

      // Timeout for the HTTP request that retrieves the homekit devices (in seconds). Default: 10
      "request_timeout": number,

      // Timeout for the service discovery (in seconds). Default: 20
      "discovery_timeout": number,
    },
    // …
  ]
}
```