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cmd/derper: add default-off debug endpoint for profiling

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Updates https://github.com/tailscale/corp/issues/11492
Signed-off-by: Tom DNetto <tom@tailscale.com>
This commit is contained in:
Tom DNetto 2023-06-07 12:58:01 -07:00
parent 1c4a047ad0
commit 4df98808da
1 changed files with 89 additions and 0 deletions
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89
cmd/derper/derper.go
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@ -12,15 +12,19 @@
"expvar"
"flag"
"fmt"
"html"
"io"
"log"
"math"
"net"
"net/http"
"net/http/pprof"
"net/netip"
"os"
"path/filepath"
"regexp"
"runtime"
"strconv"
"strings"
"time"
@ -33,6 +37,7 @@
"tailscale.com/net/stun"
"tailscale.com/tsweb"
"tailscale.com/types/key"
"tailscale.com/version"
)
var (
@ -55,6 +60,8 @@
acceptConnLimit = flag.Float64("accept-connection-limit", math.Inf(+1), "rate limit for accepting new connection")
acceptConnBurst = flag.Int("accept-connection-burst", math.MaxInt, "burst limit for accepting new connection")
debugAddr = flag.String("debug_addr", "", "listening address for debug server")
)
var (
@ -136,6 +143,7 @@ func main() {
if *dev {
*addr = ":3340" // above the keys DERP
*debugAddr = "localhost:8383"
log.Printf("Running in dev mode.")
tsweb.DevMode = true
}
@ -222,6 +230,11 @@ func main() {
go serveSTUN(listenHost, *stunPort)
}
if *debugAddr != "" {
log.Printf("running debug server on %s", *debugAddr)
go runDebugServer(*debugAddr, s)
}
quietLogger := log.New(logFilter{}, "", 0)
httpsrv := &http.Server{
Addr: *addr,
@ -513,3 +526,79 @@ func (logFilter) Write(p []byte) (int, error) {
log.Printf("%s", p)
return len(p), nil
}
func runDebugServer(addr string, s *derp.Server) {
mux := http.NewServeMux()
mux.Handle("/debug/vars", http.DefaultServeMux) // serve out expvar
mux.HandleFunc("/debug/varz", tsweb.VarzHandler) // expvar but in prometheus format
mux.HandleFunc("/debug/pprof/", pprof.Index)
mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
mux.Handle("/debug/pprofrate", http.HandlerFunc(handlePprofRate))
mux.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
w.WriteHeader(200)
fmt.Fprintf(w, `<html><body>
<h1>DERP</h1>
<p>
This is a Tailscale DERP debug server.
</p>
<ul>
<li>Version: <pre style="display: inline">%s</pre>
<li><a href="/debug/vars">/debug/vars</a> (JSON)</li>
<li><a href="/debug/varz">/debug/varz</a> (Prometheus)</li>
<li><a href="/debug/pprof">/debug/pprof</a></li>
<li><a href="/debug/pprof/goroutine?debug=1">/debug/pprof/goroutine?debug=1</a> (goroutine summary)</li>
</ul>
`, html.EscapeString(version.Long()))
}))
srv := &http.Server{
Addr: addr,
Handler: mux,
}
if err := srv.ListenAndServe(); err != nil {
if err != http.ErrServerClosed {
log.Fatal(err)
}
}
}
// handlePprofRate adjusts the pprof rate.
//
// $ curl -d block=0 http://localhost:8383/debug/pprofrate
// $ curl -d mutex=0 http://localhost:8383/debug/pprofrate
//
// See:
//
// - https://pkg.go.dev/runtime#SetMutexProfileFraction
// - https://pkg.go.dev/runtime#SetBlockProfileRate
//
// And corp#5277.
func handlePprofRate(w http.ResponseWriter, r *http.Request) {
if r.Method != "POST" {
http.Error(w, "method not allowed; want POST", http.StatusMethodNotAllowed)
return
}
if s := r.FormValue("block"); s != "" {
v, err := strconv.Atoi(s)
if err != nil {
http.Error(w, "bad block value", http.StatusBadRequest)
return
}
runtime.SetBlockProfileRate(v)
fmt.Fprintf(w, "block set to %v\n", v)
}
if s := r.FormValue("mutex"); s != "" {
v, err := strconv.Atoi(s)
if err != nil {
http.Error(w, "bad mutex value", http.StatusBadRequest)
return
}
old := runtime.SetMutexProfileFraction(v)
fmt.Fprintf(w, "mutex changed from %v to %v\n", old, v)
}
}