op-node: Add thread-safe method to check if p2p sync has a request for a block in-flight

op-node/p2p/sync.go

@@ -100,6 +100,12 @@ type peerRequest struct {
 	complete *atomic.Bool
 }
 
+type inFlightCheck struct {
+	num uint64
+
+	result chan bool
+}
+
 type SyncClientMetrics interface {
 	ClientPayloadByNumberEvent(num uint64, resultCode byte, duration time.Duration)
 	PayloadsQuarantineSize(n int)
@@ -200,6 +206,7 @@ type SyncClient struct {
 
 	requests       chan rangeRequest
 	peerRequests   chan peerRequest
+	inFlightChecks chan inFlightCheck
 
 	results chan syncResult
 
@@ -235,6 +242,7 @@ func NewSyncClient(log log.Logger, cfg *rollup.Config, newStream newStreamFn, rc
 		requests:        make(chan rangeRequest), // blocking
 		peerRequests:    make(chan peerRequest, 128),
 		results:         make(chan syncResult, 128),
+		inFlightChecks:  make(chan inFlightCheck, 128),
 		globalRL:        rate.NewLimiter(globalServerBlocksRateLimit, globalServerBlocksBurst),
 		resCtx:          ctx,
 		resCancel:       cancel,
@@ -328,6 +336,14 @@ func (s *SyncClient) mainLoop() {
 			ctx, cancel := context.WithTimeout(s.resCtx, maxResultProcessing)
 			s.onResult(ctx, res)
 			cancel()
+		case check := <-s.inFlightChecks:
+			s.log.Info("Checking in flight", "num", check.num)
+			complete, ok := s.inFlight[check.num]
+			if !ok {
+				check.result <- false
+			} else {
+				check.result <- !complete.Load()
+			}
 		case <-s.resCtx.Done():
 			s.log.Info("stopped P2P req-resp L2 block sync client")
 			return
@@ -335,6 +351,21 @@ func (s *SyncClient) mainLoop() {
 	}
 }
 
+func (s *SyncClient) isInFlight(ctx context.Context, num uint64) (bool, error) {
+	check := inFlightCheck{num: num, result: make(chan bool, 1)}
+	select {
+	case s.inFlightChecks <- check:
+	case <-ctx.Done():
+		return false, errors.New("context cancelled when publishing in flight check")
+	}
+	select {
+	case res := <-check.result:
+		return res, nil
+	case <-ctx.Done():
+		return false, errors.New("context cancelled while waiting for in flight check response")
+	}
+}
+
 // onRangeRequest is exclusively called by the main loop, and has thus direct access to the request bookkeeping state.
 // This function transforms requested block ranges into work for each peer.
 func (s *SyncClient) onRangeRequest(ctx context.Context, req rangeRequest) {

op-node/p2p/sync_test.go

@@ -271,12 +271,11 @@ func TestMultiPeerSync(t *testing.T) {
 	// Wait till the failed request is recognized as marked as done, so the re-request actually runs.
 	ctx, cancelFunc = context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancelFunc()
-	for clB.inFlight[25] != nil && !clB.inFlight[25].Load() {
-		select {
-		case <-ctx.Done():
-			t.Fatal("Did not complete request for block 25 in timely manner")
-		default:
-			// Carry on, timeout not yet reached
+	for {
+		isInFlight, err := clB.isInFlight(ctx, 25)
+		require.NoError(t, err)
+		if !isInFlight {
+			break
 		}
 		time.Sleep(time.Second)
 	}