Golang web handlers and sigpipe

main.go

package main

import (
	"bytes"
	"flag"
	"log"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"syscall"
)

func handler(w http.ResponseWriter, r *http.Request) {
	log.Println("Handling ", r.URL.Path)
	w.Header().Set("Content-type", "text/plain")
	var data bytes.Buffer
	for i := 0; i < *count*1000; i++ {
		data.Write([]byte(strconv.Itoa(i+1) + "\n"))
	}
	w.Write(data.Bytes())
}

var count = flag.Int("count", 100, "How many 1000 of numbers to print")
var catchSignal = flag.Bool("catch", false, "Should we catch sigpipe? defaults to false")

func main() {
	flag.Parse()
	if *catchSignal {
		log.Println("Will catch sigpipe")
		schan := make(chan os.Signal, 1)
		signal.Notify(schan, os.Signal(syscall.SIGPIPE))
		go func() {
			for sig := range schan {
				log.Println("Received signal ", sig)
			}

		}()
	}
	http.HandleFunc("/", handler)
	log.Fatal(http.ListenAndServe(":8080", nil))
}

output.md

No problem for your http handler with sigpipes without having to set up a handler

$ ./serve2pipe -count 1000 &
[1] 25909

$ curl -s localhost:8080|head -n 10
2018/03/21 17:50:54 Handling  /
1
2
3
4
5
6
7
8
9
10

If however you add a signal handler, you will get a callback!

$ ./serve2pipe -count 1000 -catch &
[1] 25919
[2018/03/21 17:51:46 Will catch sigpipe

$ curl -s localhost:8080|head -n 10
2018/03/21 17:51:56 Handling  /
1
2
3
4
5
6
7
8
9
10
2018/03/21 17:51:57 Received signal  broken pipe