nits

statefulsyncer/configuration.go

@@ -59,7 +59,7 @@ func WithPruneSleepTime(sleepTime int) Option {
 }
 
 // WithSeenConcurrency overrides the number of concurrent
-// invocations of BlockSeen we will make. We default
+// invocations of BlockSeen we will handle. We default
 // to the value of runtime.NumCPU().
 func WithSeenConcurrency(concurrency int64) Option {
 	return func(s *StatefulSyncer) {

statefulsyncer/stateful_syncer.go

@@ -68,9 +68,8 @@ type StatefulSyncer struct {
 	adjustmentWindow int64
 	pruneSleepTime   time.Duration
 
-	// SeenSemaphore controls how many concurrent
-	// invocations we make to the SeenBlock function
-	// in the handler.
+	// SeenSemaphore limits how many executions of
+	// BlockSeen occur concurrently.
 	seenSemaphore     *semaphore.Weighted
 	seenSemaphoreSize int64
 }

storage/modules/block_storage.go

@@ -634,7 +634,8 @@ func (b *BlockStorage) SeeBlock(
 	ctx context.Context,
 	block *types.Block,
 ) error {
-	transaction := b.db.WriteTransaction(ctx, block.BlockIdentifier.Hash, true)
+	_, key := getBlockHashKey(block.BlockIdentifier.Hash)
+	transaction := b.db.WriteTransaction(ctx, string(key), true)
 	defer transaction.Discard(ctx)
 
 	// Store all transactions in order and check for duplicates

syncer/syncer.go

@@ -555,7 +555,14 @@ func (s *Syncer) syncRange(
 	s.concurrency = startingConcurrency
 	s.goalConcurrency = s.concurrency
 
-	// Spawn syncing goroutines
+	// We create a separate derivative context here instead of
+	// replacing the provided ctx because the context returned
+	// by errgroup.WithContext is canceled as soon as Wait returns.
+	// If this canceled context is passed to a handler or helper,
+	// it can have unintended consequences (some functions
+	// return immediately if the context is canceled).
+	//
+	// Source: https://godoc.org/golang.org/x/sync/errgroup
 	g, pipelineCtx := errgroup.WithContext(ctx)
 	g.Go(func() error {
 		return s.addBlockIndices(pipelineCtx, blockIndices, s.nextIndex, endIndex)