Dump pprof when orbit is given a SIGUSR1. Fixes #8456 (#8485)

Co-authored-by: Roberto Dip <me@roperzh.com>

orbit/changes/8485-dump-pprof

@@ -0,0 +1,2 @@
+- On Unix systems, dump pprof data into a `profiles` directory in the orbit root dir
+  when receiving a SIGUSR1. This is to assist debugging for memory leaks

orbit/cmd/orbit/orbit.go

@@ -666,6 +666,8 @@ func main() {
 		defer cancel()
 		g.Add(signalHandler(ctx))
 
+		go sigusrListener(c.String("root-dir"))
+
 		if err := g.Run(); err != nil {
 			log.Error().Err(err).Msg("unexpected exit")
 		}

orbit/cmd/orbit/signal_unix.go

@@ -3,13 +3,86 @@
 package main
 
 import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
 	"context"
+	"fmt"
 	"os"
+	"os/signal"
+	"path"
+	"runtime/pprof"
 	"syscall"
+	"time"
 
+	"github.com/fleetdm/fleet/v4/orbit/pkg/constant"
+	"github.com/fleetdm/fleet/v4/pkg/secure"
 	"github.com/oklog/run"
+	"github.com/rs/zerolog/log"
 )
 
 func signalHandler(ctx context.Context) (execute func() error, interrupt func(error)) {
 	return run.SignalHandler(ctx, os.Interrupt, os.Kill, syscall.SIGTERM)
 }
+
+func sigusrListener(rootDir string) {
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, syscall.SIGUSR1)
+	for {
+		<-c
+
+		if err := dumpProf(rootDir); err != nil {
+			log.Warn().Err(err).Msg("unable to create pprof")
+		}
+	}
+}
+
+func dumpProf(rootDir string) error {
+	if err := secure.MkdirAll(path.Join(rootDir, "profiles"), constant.DefaultDirMode); err != nil {
+		return err
+	}
+	now := time.Now()
+
+	// We can't use ISO 8601/RFC 3339 because NTFS and FAT do not allow colons in filenames
+	timestamp := now.UTC().Format("2006-01-02T15-04-05")
+
+	out, err := os.Create(path.Join(rootDir, "profiles", fmt.Sprintf("profiles-%s.tar.gz", timestamp)))
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	gw := gzip.NewWriter(out)
+	defer gw.Close()
+	tw := tar.NewWriter(gw)
+	defer tw.Close()
+
+	buf := new(bytes.Buffer)
+
+	for _, profile := range pprof.Profiles() {
+		err = profile.WriteTo(buf, 0)
+		if err != nil {
+			return err
+		}
+
+		header := tar.Header{
+			Typeflag:   tar.TypeReg,
+			Name:       fmt.Sprintf("%s.pprof", profile.Name()),
+			Size:       int64(buf.Len()),
+			Mode:       0o664,
+			ModTime:    now,
+			AccessTime: now,
+			ChangeTime: now,
+		}
+		err = tw.WriteHeader(&header)
+		if err != nil {
+			return err
+		}
+		_, err = buf.WriteTo(tw)
+		if err != nil {
+			return err
+		}
+		buf.Reset()
+	}
+	return nil
+}

orbit/cmd/orbit/signal_windows.go

@@ -10,3 +10,7 @@ import (
 func signalHandler(ctx context.Context) (execute func() error, interrupt func(error)) {
 	return run.SignalHandler(ctx, os.Interrupt, os.Kill)
 }
+
+func sigusrListener(rootDir string) error {
+	return nil
+}