sync, blocks: request blocks when tortoise crossed local threshold (s…

…pacemeshos#4826)

closes: spacemeshos#4824

- first improvement is to register peers that supported blocks, otherwise we will be guessing from whom to request the block
- and when mesh is called by sync or block builder it may send request to fetch blocks from registered peers. previously it would do so only in sync code path, which is less robust and might be delayed by fork finder

mesh/mesh.go

@@ -319,15 +319,12 @@ func (msh *Mesh) ProcessLayer(ctx context.Context, lid types.LayerID) error {
 			})),
 		)
 	}
-	applicable, missing := filterMissing(results, next)
-	if len(missing) > 0 {
+	if missing := missingBlocks(results); len(missing) > 0 {
 		select {
 		case <-ctx.Done():
 		case msh.missingBlocks <- missing:
 		}
-		if len(applicable) == 0 {
-			return fmt.Errorf("%w: request missing blocks %v", ErrMissingBlock, missing)
-		}
+		return fmt.Errorf("request missing blocks %v", missing)
 	}
 
 	if err := msh.ensureStateConsistent(ctx, applicable); err != nil {

syncer/state_syncer.go

@@ -111,9 +111,7 @@ func (s *Syncer) processLayers(ctx context.Context) error {
 		// even if it fails to fetch opinions, we still go ahead to ProcessLayer so that the tortoise
 		// has a chance to count ballots and form its own opinions
 		if err := s.mesh.ProcessLayer(ctx, lid); err != nil {
-			if !errors.Is(err, mesh.ErrMissingBlock) {
-				s.logger.WithContext(ctx).With().Warning("mesh failed to process layer from sync", lid, log.Err(err))
-			}
+			s.logger.WithContext(ctx).With().Warning("mesh failed to process layer from sync", lid, log.Err(err))
 		}
 	}
 	s.logger.WithContext(ctx).With().Debug("end of state sync",