emf-http-client-gist.go

package main

import (
	"context"
	"net/http"
	"time"

	"github.com/aws/aws-lambda-go/lambda"
	"github.com/prozz/aws-embedded-metrics-golang/emf"
)

type loggingRoundTripper struct {
	Proxied http.RoundTripper
}

func (t loggingRoundTripper) RoundTrip(req *http.Request) (res *http.Response, e error) {
	m := emf.New().Namespace("CustomNamespace")
	defer m.Log()

	start := time.Now()
	res, e = t.Proxied.RoundTrip(req)
	elapsed := time.Since(start)

	m.DimensionSet(
		emf.NewDimension("Endpoint", req.Host),
		emf.NewDimension("Operation", req.Method)).
		MetricFloatAs("Duration", elapsed.Seconds(), emf.Seconds)

	clientErr := 0
	serverErr := 0
	success := 0
	if res.StatusCode >= 200 && res.StatusCode < 300 {
		success = 1
	}
	if res.StatusCode >= 500 {
		serverErr = 1
	}
	if res.StatusCode >= 400 && res.StatusCode < 500 {
		clientErr = 1
	}

	m.MetricAs("Error", clientErr, emf.Count)
	m.MetricAs("Fatal", serverErr, emf.Count)
	m.MetricAs("Success", success, emf.Count)

	return
}

func handler(ctx context.Context, event MyEvent) (string, error) {
	var c = &http.Client{Transport: loggingRoundTripper{http.DefaultTransport}}
	c.Get(event.URL)
	return "done", nil
}

func main() {
	lambda.Start(handler)
}

type MyEvent struct {
	URL string `json:"url"`
}