Particle, Cloud Functions & Prometheus

function.go

package q

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"strconv"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/push"
)

type data struct {
	Event     string `json:"event"`
	Data      string `json:"data"`
	Published string `json:"published_at"`
	CoreID    string `json:"coreid"`
}

// ToPushGateway marshals then sends a particle.io webhook event to a Prometheus PushGateway
func ToPushGateway(w http.ResponseWriter, r *http.Request) {
	log.Println("function")
	gateway := os.Getenv("GATEWAY")
	if gateway == "" {
		log.Fatal("No Prometheus PushGateway defined")
	}

	var d data
	if err := json.NewDecoder(r.Body).Decode(&d); err != nil {
		fmt.Fprint(w, err)
		return
	}

	percentGauge := prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "percent",
		Help: "The percentage humidity.",
	})

	percent, err := strconv.ParseFloat(d.Data, 64)
	if err != nil {
		log.Fatal(err)
	}

	log.Printf("value: %f", percent)
	percentGauge.Set(percent)
	if err := push.New(fmt.Sprintf("http://%s", gateway), "pushgateway").
		Collector(percentGauge).
		Grouping("core_id", d.CoreID).
		Push(); err != nil {
		log.Print(err)
	}

	fmt.Fprint(w, "ok")
}

go.mod

module cloudfunction

go 1.12

require github.com/prometheus/client_golang v1.0.0 // indirect