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main.go
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main.go
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package main
import (
"context"
"flag"
"io"
"log"
"net/http"
"net/url"
"os"
"os/signal"
"regexp"
"strings"
"syscall"
)
var (
availablePath = flag.String("available-path", "/readyz", "Allowed path for requests")
addr = flag.String("serve-addr", ":8080", "Addr to serve requests")
allowedHosts = flag.String("allowed-hosts", "", "Allowed hosts for requests (regex)")
)
func main() {
flag.Parse()
isAllowed := allowedHostsNoop
if *allowedHosts != "" {
var err error
isAllowed, err = allowedHostsRegex(*allowedHosts)
if err != nil {
log.Fatal(err.Error())
}
}
handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
u, err := url.Parse(strings.TrimLeft(r.URL.Path, "/"))
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
if u.Path != *availablePath || !isAllowed(u.Hostname()) {
http.Error(w, "404 not found", http.StatusNotFound)
return
}
res, err := http.DefaultClient.Get(u.String())
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
defer res.Body.Close()
w.WriteHeader(res.StatusCode)
_, _ = io.Copy(w, res.Body)
})
srv := &http.Server{
Addr: *addr,
Handler: handler,
}
if err := srv.ListenAndServe(); err != nil {
log.Fatal(err.Error())
}
log.Println("signal ", Wait([]os.Signal{syscall.SIGTERM, syscall.SIGINT}).String())
if err := srv.Shutdown(context.Background()); err != nil {
log.Fatal(err.Error())
}
}
func Wait(signals []os.Signal) os.Signal {
sig := make(chan os.Signal, len(signals))
signal.Notify(sig, signals...)
return <-sig
}
func allowedHostsNoop(_ string) bool {
return true
}
func allowedHostsRegex(allowedRegex string) (func(string) bool, error) {
r, err := regexp.Compile(allowedRegex)
if err != nil {
return nil, err
}
return func(s string) bool {
return r.MatchString(s)
}, nil
}