README.md

swarmprom

This library provides a secure way to expose the Prometheus metrics http handler in a docker swarm environment. The access to the handler is only allowed for containers beloging to the configured swarm service. The relevant ip addresses are obtained from the swarm dns service discovery mechanism.

Usage

Use the prometheus primitives to setup your monitoring environment. Just use swarmprom.Handler() as the handler for your HTTP server instance. As argument you have to supply the name of the swarm service prometheus is reachable by.

import (
    "github.com/faryon93/swarmprom"
    "github.com/prometheus/client_golang/prometheus"
)

func main() {
    // register prometheus metrics
    var counter = prometheus.NewCounter(prometheus.CounterOpts{
        Namespace: "namespace",
        Subsystem: "subsystem",
        Name:      "test_total",
        Help:      "Total number of tests.",
    })
    prometheus.MustRegister(counter)

    // expose http endpoint
    http.Handle("/metrics", swarmprom.Handler("prometheus"))
    http.ListenAndServe(":8080", nil)
}

Customization

To define a custom handler function in case the access get rejected use swarmprom.SetRejectHandler():

swarmprom.SetRejectHandler(func(w http.ResponseWriter, r *http.Request) {
    http.Error(w, "Nice night for a walk!", http.StatusNotFound)
})

To use a custom logging entry use swarmprom.SetLogger():

swarmprom.SetLogger(logrus.WithField("handler", "prometheus"))