tsweb: add stack trace to panic error msg

Updates #12784

Signed-off-by: Paul Scott <paul@tailscale.com>
pull/12815/head
Paul Scott 4 months ago committed by Paul Scott
parent fd0acc4faf
commit fec41e4904

@ -20,6 +20,7 @@ import (
"os"
"path/filepath"
"regexp"
"runtime"
"strconv"
"strings"
"sync"
@ -356,6 +357,13 @@ func (h retHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
)
defer func() {
if didPanic {
// TODO(icio): When the panic below is eventually caught by
// http.Server, it cancels the inlight request and the "500 Internal
// Server Error" response we wrote to the client below is never
// received, even if we flush it.
if f, ok := w.(http.Flusher); ok {
f.Flush()
}
panic(panicRes)
}
}()
@ -364,10 +372,16 @@ func (h retHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if r := recover(); r != nil {
didPanic = true
panicRes = r
// Even if r is an error, do not wrap it as an error here as
// that would allow things like panic(vizerror.New("foo")) which
// is really hard to define the behavior of.
err = fmt.Errorf("panic: %v", r)
if r == http.ErrAbortHandler {
err = http.ErrAbortHandler
} else {
// Even if r is an error, do not wrap it as an error here as
// that would allow things like panic(vizerror.New("foo")) which
// is really hard to define the behavior of.
var stack [10000]byte
n := runtime.Stack(stack[:], false)
err = fmt.Errorf("panic: %v\n\n%s", r, stack[:n])
}
}
}()
return h.rh.ServeHTTPReturn(lw, r)

@ -8,11 +8,13 @@ import (
"context"
"errors"
"fmt"
"io"
"net"
"net/http"
"net/http/httptest"
"net/url"
"strings"
"sync/atomic"
"testing"
"time"
@ -527,6 +529,82 @@ func TestStdHandler(t *testing.T) {
}
}
func TestStdHandler_Panic(t *testing.T) {
var r AccessLogRecord
h := StdHandler(
ReturnHandlerFunc(func(w http.ResponseWriter, r *http.Request) error {
panicElsewhere()
return nil
}),
HandlerOptions{
Logf: t.Logf,
OnCompletion: func(_ *http.Request, alr AccessLogRecord) {
r = alr
},
},
)
// Run our panicking handler in a http.Server which catches and rethrows
// any panics.
var recovered atomic.Value
s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
defer func() {
if r := recovered.Load(); r != nil {
panic(r)
}
}()
defer func() {
recovered.Store(recover())
}()
h.ServeHTTP(w, r)
}))
t.Cleanup(s.Close)
// Send a request to our server.
res, err := http.Get(s.URL)
if err != nil {
t.Fatal(err)
}
if recovered.Load() == nil {
t.Fatal("expected panic but saw none")
}
// Check that the log message contained the stack trace in the error.
var logerr bool
if p := "panic: panicked elsewhere\n\ngoroutine "; !strings.HasPrefix(r.Err, p) {
t.Errorf("got error prefix %q, want %q", r.Err[:min(len(r.Err), len(p))], p)
logerr = true
}
if s := "\ntailscale.com/tsweb.panicElsewhere("; !strings.Contains(r.Err, s) {
t.Errorf("want substr %q, not found", s)
logerr = true
}
if logerr {
t.Logf("logger got error: (quoted) %q\n\n(verbatim)\n%s", r.Err, r.Err)
}
t.Run("check_response", func(t *testing.T) {
// TODO(icio): Swallow panics? tailscale/tailscale#12784
t.SkipNow()
// Check that the server sent an error response.
if res.StatusCode != 500 {
t.Errorf("got status code %d, want %d", res.StatusCode, 500)
}
body, err := io.ReadAll(res.Body)
if err != nil {
t.Errorf("error reading body: %s", err)
} else if want := "internal server error\n"; string(body) != want {
t.Errorf("got body %q, want %q", body, want)
}
res.Body.Close()
})
}
func panicElsewhere() {
panic("panicked elsewhere")
}
func BenchmarkLogNot200(b *testing.B) {
b.ReportAllocs()
rh := handlerFunc(func(w http.ResponseWriter, r *http.Request) error {

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