A very simple healthcheck loop

check.go

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"time"
)

func main() {
	if len(os.Args) < 2 {
		fmt.Fprintf(os.Stderr, "please supply a url to check")
		os.Exit(1)
	}

	checkURL := os.Args[1]

	var check *url.URL
	var err error
	check, err = url.ParseRequestURI(checkURL)
	if err != nil {
		fmt.Fprintf(os.Stderr, "err")
		os.Exit(1)
	}

	var req *http.Request
	req, err = http.NewRequest("GET", check.String(), nil)
	if err != nil {
		fmt.Fprintf(os.Stderr, "err")
		os.Exit(1)
	}

	client := &http.Client{
		Timeout: 5 * time.Second,
		Transport: &http.Transport{
			IdleConnTimeout:       30 * time.Second,
			ResponseHeaderTimeout: 5 * time.Second,
		},
	}

	tick := time.Tick(10 * time.Second)
	var res *http.Response
	var start time.Time
	var now string
	var contentLength int64
	for {
		select {
		case <-tick:
			start = time.Now()
			res, err = client.Do(req)
			now = time.Now().UTC().Format(time.RFC3339)
			if err != nil {
				fmt.Fprintf(os.Stderr, "%s %s %+v (%v)\n", now, check.String(), err, time.Since(start))
				continue
			}
			defer res.Body.Close()

			contentLength, err = io.Copy(ioutil.Discard, res.Body)
			if err != nil {
				fmt.Fprintf(os.Stderr, "%s %s %+v (%v)\n", now, check.String(), err, time.Since(start))
				continue
			}

			if res.StatusCode > 299 {
				fmt.Fprintf(os.Stderr, "%s %s status code: %v (%v)\n", now, check.String(), res.StatusCode, time.Since(start))
				continue
			}
			fmt.Fprintf(os.Stdout, "%s %s %v (%v)\n", now, check.String(), contentLength, time.Since(start))
		}
	}
}