# Enable Prometheus metrics in Caddy


The [Caddy webserver](https://caddyserver.com/) is a modern webserver written in Go.
I like it because I can easily extend it by writing some middleware (in
Go). One of the things missing is
[metrics](https://github.com/mholt/caddy/issues/577), which prompted me
to implement [enough metrics](https://github.com/miekg/caddy-prometheus/) to make me happy.

Using this is relatively straight forward, but you'll need to compile Caddy yourself and add this
middleware.

## Setup

(Assuming you have Go installed), first get the goodies:

Caddy:
:   `go get github.com/mholt/caddy`

Caddyext:
:   This is needed to compile in the new middleware, `go get
github.com/caddyserver/caddyext`

Caddy-prometheus:
:   `go get github.com/miekg/caddy-prometheus`

Then, with `caddyext` register the new middleware:
~~~
caddyext install prometheus:github.com/miekg/caddy-prometheus
~~~
Optionally you can check your middleware stack with `caddyext stack`, but
be sure to move prometheus early in the stack:
~~~
caddyext move prometheus 0
~~~
Now compile your new Caddy:
~~~
caddyext build
~~~
This should create a `customCaddy` binary which you can run. To enable metrics
you'll need to add the directive `prometheus` to each host section that you'll
want metrics for. The default address and path for the metrics's is `http://localhost:9180/metrics`

Curling this should result in something like this:
~~~ text
caddy_http_request_count_total{host="archive.miek.nl"} 1416
caddy_http_request_duration_seconds_bucket{host="archive.miek.nl",le="0.005"} 1338
caddy_http_request_duration_seconds_bucket{host="archive.miek.nl",le="0.01"} 1370
caddy_http_request_duration_seconds_bucket{host="archive.miek.nl",le="0.025"} 1396
caddy_http_request_duration_seconds_bucket{host="archive.miek.nl",le="0.05"} 1396
caddy_http_request_duration_seconds_bucket{host="archive.miek.nl",le="0.1"} 1396
...
~~~

## Grafana and Metrics

Then if you are running  [prometheus and grafana](https://miek.nl/2016/february/24/monitoring-with-ssh-and-prometheus/) you can the query and
plot neat graphs.
For instance plotting number of qps for `miek.nl`, can be done with
`sum(rate(caddy_http_request_count_total{host=~"miek.nl"}[5m])) by (instance)`, which results on
my (highly popular web site):

{{<figure src="/images/2016/caddy-prometheus.png" caption="Queries per second for miek.nl.">}}

Some day I hope to hit 1 qps.