all: Send deadlocks as failures, crash only as a last resort (#7785)

cmd/stcrashreceiver/main.go

@@ -19,10 +19,9 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
-	"net"
 	"net/http"
 	"os"
-	"time"
+	"path/filepath"
 
 	"github.com/syncthing/syncthing/lib/sha256"
 	"github.com/syncthing/syncthing/lib/ur"
@@ -33,7 +32,7 @@ import (
 const maxRequestSize = 1 << 20 // 1 MiB
 
 func main() {
-	dir := flag.String("dir", ".", "Directory to store reports in")
+	dir := flag.String("dir", ".", "Parent directory to store crash and failure reports in")
 	dsn := flag.String("dsn", "", "Sentry DSN")
 	listen := flag.String("listen", ":22039", "HTTP listen address")
 	flag.Parse()
@@ -41,13 +40,13 @@ func main() {
 	mux := http.NewServeMux()
 
 	cr := &crashReceiver{
-		dir: *dir,
+		dir: filepath.Join(*dir, "crash_reports"),
 		dsn: *dsn,
 	}
 	mux.Handle("/", cr)
 
 	if *dsn != "" {
-		mux.HandleFunc("/newcrash/failure", handleFailureFn(*dsn))
+		mux.HandleFunc("/newcrash/failure", handleFailureFn(*dsn, filepath.Join(*dir, "failure_reports")))
 	}
 
 	log.SetOutput(os.Stdout)
@@ -56,7 +55,7 @@ func main() {
 	}
 }
 
-func handleFailureFn(dsn string) func(w http.ResponseWriter, req *http.Request) {
+func handleFailureFn(dsn, failureDir string) func(w http.ResponseWriter, req *http.Request) {
 	return func(w http.ResponseWriter, req *http.Request) {
 		lr := io.LimitReader(req.Body, maxRequestSize)
 		bs, err := ioutil.ReadAll(lr)
@@ -89,6 +88,18 @@ func handleFailureFn(dsn string) func(w http.ResponseWriter, req *http.Request)
 			pkt.Extra = raven.Extra{
 				"count": r.Count,
 			}
+			for k, v := range r.Extra {
+				pkt.Extra[k] = v
+			}
+			if len(r.Goroutines) != 0 {
+				url, err := saveFailureWithGoroutines(r.FailureData, failureDir)
+				if err != nil {
+					log.Println("Saving failure report:", err)
+					http.Error(w, "Internal server error", http.StatusInternalServerError)
+					return
+				}
+				pkt.Extra["goroutinesURL"] = url
+			}
 			message := sanitizeMessageLDB(r.Description)
 			pkt.Fingerprint = []string{message}
 
@@ -101,19 +112,15 @@ func handleFailureFn(dsn string) func(w http.ResponseWriter, req *http.Request)
 	}
 }
 
-// userIDFor returns a string we can use as the user ID for the purpose of
-// counting affected users. It's the truncated hash of a salt, the user
-// remote IP, and the current month.
-func userIDFor(req *http.Request) string {
-	addr := req.RemoteAddr
-	if fwd := req.Header.Get("x-forwarded-for"); fwd != "" {
-		addr = fwd
-	}
-	if host, _, err := net.SplitHostPort(addr); err == nil {
-		addr = host
+func saveFailureWithGoroutines(data ur.FailureData, failureDir string) (string, error) {
+	bs := make([]byte, len(data.Description)+len(data.Goroutines))
+	copy(bs, data.Description)
+	copy(bs[len(data.Description):], data.Goroutines)
+	id := fmt.Sprintf("%x", sha256.Sum256(bs))
+	path := fullPathCompressed(failureDir, id)
+	err := compressAndWrite(bs, path)
+	if err != nil {
+		return "", err
 	}
-	now := time.Now().Format("200601")
-	salt := "stcrashreporter"
-	hash := sha256.Sum256([]byte(salt + addr + now))
-	return fmt.Sprintf("%x", hash[:8])
+	return reportServer + path, nil
 }

cmd/stcrashreceiver/util.go

@@ -0,0 +1,57 @@
+// Copyright (C) 2021 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package main
+
+import (
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"path/filepath"
+	"time"
+
+	"github.com/syncthing/syncthing/lib/sha256"
+)
+
+// userIDFor returns a string we can use as the user ID for the purpose of
+// counting affected users. It's the truncated hash of a salt, the user
+// remote IP, and the current month.
+func userIDFor(req *http.Request) string {
+	addr := req.RemoteAddr
+	if fwd := req.Header.Get("x-forwarded-for"); fwd != "" {
+		addr = fwd
+	}
+	if host, _, err := net.SplitHostPort(addr); err == nil {
+		addr = host
+	}
+	now := time.Now().Format("200601")
+	salt := "stcrashreporter"
+	hash := sha256.Sum256([]byte(salt + addr + now))
+	return fmt.Sprintf("%x", hash[:8])
+}
+
+// 01234567890abcdef... => 01/23
+func dirFor(base string) string {
+	return filepath.Join(base[0:2], base[2:4])
+}
+
+func fullPathCompressed(root, reportID string) string {
+	return filepath.Join(root, dirFor(reportID), reportID) + ".gz"
+}
+
+func compressAndWrite(bs []byte, fullPath string) error {
+	// Compress the report for storage
+	buf := new(bytes.Buffer)
+	gw := gzip.NewWriter(buf)
+	_, _ = gw.Write(bs) // can't fail
+	gw.Close()
+
+	// Create an output file with the compressed report
+	return ioutil.WriteFile(fullPath, buf.Bytes(), 0644)
+}

lib/model/model.go

@@ -324,7 +324,7 @@ func (m *model) fatal(err error) {
 // period.
 func (m *model) StartDeadlockDetector(timeout time.Duration) {
 	l.Infof("Starting deadlock detector with %v timeout", timeout)
-	detector := newDeadlockDetector(timeout)
+	detector := newDeadlockDetector(timeout, m.evLogger, m.fatal)
 	detector.Watch("fmut", m.fmut)
 	detector.Watch("pmut", m.pmut)
 }

lib/model/util.go

@@ -9,61 +9,100 @@ package model
 import (
 	"fmt"
 	"path/filepath"
+	"strings"
 	"sync"
 	"time"
 
 	"github.com/pkg/errors"
+	"github.com/syncthing/syncthing/lib/events"
 	"github.com/syncthing/syncthing/lib/fs"
+	"github.com/syncthing/syncthing/lib/ur"
 )
 
 type Holdable interface {
 	Holders() string
 }
 
-func newDeadlockDetector(timeout time.Duration) *deadlockDetector {
+func newDeadlockDetector(timeout time.Duration, evLogger events.Logger, fatal func(error)) *deadlockDetector {
 	return &deadlockDetector{
-		timeout: timeout,
-		lockers: make(map[string]sync.Locker),
+		warnTimeout:  timeout,
+		fatalTimeout: 10 * timeout,
+		lockers:      make(map[string]sync.Locker),
+		evLogger:     evLogger,
+		fatal:        fatal,
 	}
 }
 
 type deadlockDetector struct {
-	timeout time.Duration
-	lockers map[string]sync.Locker
+	warnTimeout, fatalTimeout time.Duration
+	lockers                   map[string]sync.Locker
+	evLogger                  events.Logger
+	fatal                     func(error)
 }
 
 func (d *deadlockDetector) Watch(name string, mut sync.Locker) {
 	d.lockers[name] = mut
 	go func() {
 		for {
-			time.Sleep(d.timeout / 4)
-			ok := make(chan bool, 2)
+			time.Sleep(d.warnTimeout / 4)
+			done := make(chan struct{}, 1)
 
 			go func() {
 				mut.Lock()
 				_ = 1 // empty critical section
 				mut.Unlock()
-				ok <- true
+				done <- struct{}{}
 			}()
 
-			go func() {
-				time.Sleep(d.timeout)
-				ok <- false
-			}()
-
-			if r := <-ok; !r {
-				msg := fmt.Sprintf("deadlock detected at %s", name)
-				for otherName, otherMut := range d.lockers {
-					if otherHolder, ok := otherMut.(Holdable); ok {
-						msg += "\n===" + otherName + "===\n" + otherHolder.Holders()
-					}
-				}
-				panic(msg)
-			}
+			d.watchInner(name, done)
 		}
 	}()
 }
 
+func (d *deadlockDetector) watchInner(name string, done chan struct{}) {
+	warn := time.NewTimer(d.warnTimeout)
+	fatal := time.NewTimer(d.fatalTimeout)
+	defer func() {
+		warn.Stop()
+		fatal.Stop()
+	}()
+
+	select {
+	case <-warn.C:
+		failure := ur.FailureDataWithGoroutines(fmt.Sprintf("potential deadlock detected at %s (short timeout)", name))
+		failure.Extra["timeout"] = d.warnTimeout.String()
+		d.evLogger.Log(events.Failure, failure)
+	case <-done:
+		return
+	}
+
+	select {
+	case <-fatal.C:
+		err := fmt.Errorf("potential deadlock detected at %s (long timeout)", name)
+		failure := ur.FailureDataWithGoroutines(err.Error())
+		failure.Extra["timeout"] = d.fatalTimeout.String()
+		others := d.otherHolders()
+		failure.Extra["other-holders"] = others
+		d.evLogger.Log(events.Failure, failure)
+		d.fatal(err)
+		// Give it a minute to shut down gracefully, maybe shutting down
+		// can get out of the deadlock (or it's not really a deadlock).
+		time.Sleep(time.Minute)
+		panic(fmt.Sprintf("%v:\n%v", err, others))
+	case <-done:
+	}
+}
+
+func (d *deadlockDetector) otherHolders() string {
+	var b strings.Builder
+	for otherName, otherMut := range d.lockers {
+		if otherHolder, ok := otherMut.(Holdable); ok {
+			b.WriteString("===" + otherName + "===\n" + otherHolder.Holders() + "\n")
+		}
+	}
+	return b.String()
+}
+
 // inWritableDir calls fn(path), while making sure that the directory
 // containing `path` is writable for the duration of the call.
 func inWritableDir(fn func(string) error, targetFs fs.Filesystem, path string, ignorePerms bool) error {

lib/ur/failurereporting.go

@@ -11,6 +11,8 @@ import (
 	"context"
 	"encoding/json"
 	"net/http"
+	"runtime/pprof"
+	"strings"
 	"time"
 
 	"github.com/syncthing/syncthing/lib/build"
@@ -35,9 +37,24 @@ var (
 )
 
 type FailureReport struct {
+	FailureData
+	Count   int
+	Version string
+}
+
+type FailureData struct {
 	Description string
-	Count       int
-	Version     string
+	Goroutines  string
+	Extra       map[string]string
+}
+
+func FailureDataWithGoroutines(description string) FailureData {
+	var buf *strings.Builder
+	pprof.NewProfile("goroutine").WriteTo(buf, 1)
+	return FailureData{
+		Description: description,
+		Goroutines:  buf.String(),
+	}
 }
 
 type FailureHandler interface {
@@ -64,6 +81,7 @@ type failureHandler struct {
 type failureStat struct {
 	first, last time.Time
 	count       int
+	data        FailureData
 }
 
 func (h *failureHandler) Serve(ctx context.Context) error {
@@ -82,23 +100,28 @@ func (h *failureHandler) Serve(ctx context.Context) error {
 			if !ok {
 				// Just to be safe - shouldn't ever happen, as
 				// evChan is set to nil when unsubscribing.
-				h.addReport(evChanClosed, time.Now())
+				h.addReport(FailureData{Description: evChanClosed}, time.Now())
 				evChan = nil
 				continue
 			}
-			descr, ok := e.Data.(string)
-			if !ok {
+			var data FailureData
+			switch d := e.Data.(type) {
+			case string:
+				data.Description = d
+			case FailureData:
+				data = d
+			default:
 				// Same here, shouldn't ever happen.
-				h.addReport(invalidEventDataType, time.Now())
+				h.addReport(FailureData{Description: invalidEventDataType}, time.Now())
 				continue
 			}
-			h.addReport(descr, e.Time)
+			h.addReport(data, e.Time)
 		case <-timer.C:
 			reports := make([]FailureReport, 0, len(h.buf))
 			now := time.Now()
 			for descr, stat := range h.buf {
 				if now.Sub(stat.last) > minDelay || now.Sub(stat.first) > maxDelay {
-					reports = append(reports, newFailureReport(descr, stat.count))
+					reports = append(reports, newFailureReport(stat))
 					delete(h.buf, descr)
 				}
 			}
@@ -125,8 +148,8 @@ func (h *failureHandler) Serve(ctx context.Context) error {
 		sub.Unsubscribe()
 		if len(h.buf) > 0 {
 			reports := make([]FailureReport, 0, len(h.buf))
-			for descr, stat := range h.buf {
-				reports = append(reports, newFailureReport(descr, stat.count))
+			for _, stat := range h.buf {
+				reports = append(reports, newFailureReport(stat))
 			}
 			timeout, cancel := context.WithTimeout(context.Background(), finalSendTimeout)
 			defer cancel()
@@ -151,16 +174,17 @@ func (h *failureHandler) applyOpts(opts config.OptionsConfiguration, sub events.
 	return url, nil, nil
 }
 
-func (h *failureHandler) addReport(descr string, evTime time.Time) {
-	if stat, ok := h.buf[descr]; ok {
+func (h *failureHandler) addReport(data FailureData, evTime time.Time) {
+	if stat, ok := h.buf[data.Description]; ok {
 		stat.last = evTime
 		stat.count++
 		return
 	}
-	h.buf[descr] = &failureStat{
+	h.buf[data.Description] = &failureStat{
 		first: evTime,
 		last:  evTime,
 		count: 1,
+		data:  data,
 	}
 }
 
@@ -210,10 +234,10 @@ func sendFailureReports(ctx context.Context, reports []FailureReport, url string
 	return
 }
 
-func newFailureReport(descr string, count int) FailureReport {
+func newFailureReport(stat *failureStat) FailureReport {
 	return FailureReport{
-		Description: descr,
-		Count:       count,
+		FailureData: stat.data,
+		Count:       stat.count,
 		Version:     build.LongVersion,
 	}
 }

lib/ur/usage_report.go

@@ -23,8 +23,8 @@ import (
 	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/config"
 	"github.com/syncthing/syncthing/lib/connections"
+	"github.com/syncthing/syncthing/lib/db"
 	"github.com/syncthing/syncthing/lib/dialer"
-	"github.com/syncthing/syncthing/lib/model"
 	"github.com/syncthing/syncthing/lib/protocol"
 	"github.com/syncthing/syncthing/lib/scanner"
 	"github.com/syncthing/syncthing/lib/upgrade"
@@ -38,15 +38,20 @@ const Version = 3
 
 var StartTime = time.Now().Truncate(time.Second)
 
+type Model interface {
+	DBSnapshot(folder string) (*db.Snapshot, error)
+	UsageReportingStats(report *contract.Report, version int, preview bool)
+}
+
 type Service struct {
 	cfg                config.Wrapper
-	model              model.Model
+	model              Model
 	connectionsService connections.Service
 	noUpgrade          bool
 	forceRun           chan struct{}
 }
 
-func New(cfg config.Wrapper, m model.Model, connectionsService connections.Service, noUpgrade bool) *Service {
+func New(cfg config.Wrapper, m Model, connectionsService connections.Service, noUpgrade bool) *Service {
 	return &Service{
 		cfg:                cfg,
 		model:              m,