Particle, OpenCensus & MicroK8s

function.go

package p

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

	"contrib.go.opencensus.io/exporter/ocagent"
	"go.opencensus.io/stats"
	"go.opencensus.io/stats/view"
	"go.opencensus.io/tag"
)

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

var (
	keyCoreID tag.Key
	mPercent  *stats.Float64Measure
)

func init() {
	log.Println("init")
	serviceName := os.Getenv("SERVICE_NAME")
	if serviceName == "" {
		serviceName = "particle"
	}
	log.Printf("Service: %s", serviceName)
	agentEndpoint := os.Getenv("AGENT_ENDPOINT")
	if agentEndpoint == "" {
		log.Fatal("Requires AGENT_ENDPOINT environment variable")
	}
	log.Printf("OpenCensus Agent: %s", agentEndpoint)

	oce, err := ocagent.NewExporter(
		ocagent.WithInsecure(),
		ocagent.WithAddress(agentEndpoint),
		ocagent.WithServiceName(serviceName),
	)
	if err != nil {
		log.Fatal(err)
	}
	// defer oce.Stop()

	view.RegisterExporter(oce)

	view.SetReportingPeriod(5 * time.Second)

	// Defined at Package level
	keyCoreID, _ = tag.NewKey("CoreID")
	mPercent = stats.Float64("percent", "The percent value from the humidity sensor", "1")

	views := []*view.View{
		{
			Name:        "dist",
			Description: "The percent values",
			Measure:     mPercent,
			Aggregation: view.Distribution(10, 20, 30, 40, 50, 60, 70, 80, 90, 100),
			TagKeys:     []tag.Key{keyCoreID},
		},
		{
			Name:        "percent",
			Description: "The percent values",
			Measure:     mPercent,
			Aggregation: view.Count(),
			TagKeys:     []tag.Key{keyCoreID},
		},
	}

	if err := view.Register(views...); err != nil {
		log.Fatal(err)
	}
}

// Percent is a Cloud Function | Handler
func Percent(w http.ResponseWriter, r *http.Request) {
	log.Println("percent")
	var d data
	if err := json.NewDecoder(r.Body).Decode(&d); err != nil {
		fmt.Fprint(w, err)
		return
	}

	ctx, _ := tag.New(context.Background(),
		tag.Upsert(keyCoreID, d.CoreID),
	)
	percent, err := strconv.ParseFloat(d.Data, 64)
	if err != nil {
		log.Fatal(err)
	}
	log.Printf("value: %f", percent)
	stats.Record(ctx, mPercent.M(percent))

  fmt.Fprint(w, "ok")
}