// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// The derpprobe binary probes derpers.
package main
import (
"expvar"
"flag"
"fmt"
"html"
"io"
"log"
"net/http"
"sort"
"time"
"tailscale.com/prober"
"tailscale.com/tsweb"
)
var (
derpMapURL = flag.String("derp-map", "https://login.tailscale.com/derpmap/default", "URL to DERP map (https:// or file://)")
listen = flag.String("listen", ":8030", "HTTP listen address")
probeOnce = flag.Bool("once", false, "probe once and print results, then exit; ignores the listen flag")
interval = flag.Duration("interval", 15*time.Second, "probe interval")
)
func main() {
flag.Parse()
p := prober.New().WithSpread(true).WithOnce(*probeOnce)
dp, err := prober.DERP(p, *derpMapURL, *interval, *interval, *interval)
if err != nil {
log.Fatal(err)
}
p.Run("derpmap-probe", *interval, nil, dp.ProbeMap)
if *probeOnce {
log.Printf("Waiting for all probes (may take up to 1m)")
p.Wait()
st := getOverallStatus(p)
for _, s := range st.good {
log.Printf("good: %s", s)
}
for _, s := range st.bad {
log.Printf("bad: %s", s)
}
return
}
mux := http.NewServeMux()
tsweb.Debugger(mux)
expvar.Publish("derpprobe", p.Expvar())
mux.HandleFunc("/", http.HandlerFunc(serveFunc(p)))
log.Fatal(http.ListenAndServe(*listen, mux))
}
type overallStatus struct {
good, bad []string
}
func (st *overallStatus) addBadf(format string, a ...any) {
st.bad = append(st.bad, fmt.Sprintf(format, a...))
}
func (st *overallStatus) addGoodf(format string, a ...any) {
st.good = append(st.good, fmt.Sprintf(format, a...))
}
func getOverallStatus(p *prober.Prober) (o overallStatus) {
for p, i := range p.ProbeInfo() {
if i.End.IsZero() {
// Do not show probes that have not finished yet.
continue
}
if i.Result {
o.addGoodf("%s: %s", p, i.Latency)
} else {
o.addBadf("%s: %s", p, i.Error)
}
}
sort.Strings(o.bad)
sort.Strings(o.good)
return
}
func serveFunc(p *prober.Prober) func(w http.ResponseWriter, r *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
st := getOverallStatus(p)
summary := "All good"
if (float64(len(st.bad)) / float64(len(st.bad)+len(st.good))) > 0.25 {
// Returning a 500 allows monitoring this server externally and configuring
// an alert on HTTP response code.
w.WriteHeader(500)
summary = fmt.Sprintf("%d problems", len(st.bad))
}
io.WriteString(w, "\n")
fmt.Fprintf(w, "derp probe
\n%s:", summary)
for _, s := range st.bad {
fmt.Fprintf(w, "- %s
\n", html.EscapeString(s))
}
for _, s := range st.good {
fmt.Fprintf(w, "- %s
\n", html.EscapeString(s))
}
io.WriteString(w, "
\n")
}
}