Add panic handler (#3296)

beacon-chain/sync/subscriber.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"runtime/debug"
 	"time"
 
 	"github.com/gogo/protobuf/proto"
@@ -85,6 +86,13 @@ func (r *RegularSync) subscribe(topic string, validate validator, handle subHand
 	// Pipeline decodes the incoming subscription data, runs the validation, and handles the
 	// message.
 	pipeline := func(data []byte) {
+		defer func() {
+			if r := recover(); r != nil {
+				log.WithField("error", r).Error("Panic occurred")
+				debug.PrintStack()
+			}
+		}()
+		
 		if data == nil {
 			log.Warn("Received nil message on pubsub")
 			return

beacon-chain/sync/subscriber_test.go

@@ -38,3 +38,26 @@ func TestSubscribe_ReceivesValidMessage(t *testing.T) {
 		t.Fatal("Did not receive PubSub in 1 second")
 	}
 }
+
+func TestSubscribe_HandlesPanic(t *testing.T) {
+	p2p := p2ptest.NewTestP2P(t)
+	r := RegularSync{
+		ctx: context.Background(),
+		p2p: p2p,
+	}
+
+	topic := "/eth2/voluntary_exit"
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	r.subscribe(topic, noopValidator, func(_ context.Context, msg proto.Message) error {
+		defer wg.Done()
+		panic("bad")
+	})
+
+	p2p.ReceivePubSub(topic, &pb.VoluntaryExit{Epoch: 55})
+
+	if testutil.WaitTimeout(&wg, time.Second) {
+		t.Fatal("Did not receive PubSub in 1 second")
+	}
+}