Fix tracker errors after a block reorganization (#247)

* Fix blocktraceker.go and tracker.go after block reorganization

* func (t *BlockTracker) Init() fix

* include getBlockByNumber() into Tracker

---------

Co-authored-by: Igor Crevar <crewce@gmail.com>

blocktracker/blocktracker.go

@@ -113,6 +113,11 @@ func (t *BlockTracker) Init() (err error) {
 			}
 			block, err = t.provider.GetBlockByHash(block.ParentHash, false)
 			if err != nil {
+				return
+			} else if block == nil {
+				// if block does not exist (for example reorg happened) GetBlockByHash will return nil, nil
+				err = fmt.Errorf("block with hash %s not found", block.ParentHash)
+
 				return
 			}
 		}
@@ -231,6 +236,9 @@ func (t *BlockTracker) handleReconcileImpl(block *ethgo.Block) ([]*ethgo.Block,
 
 		parent, err := t.provider.GetBlockByHash(block.ParentHash, false)
 		if err != nil {
+			return nil, -1, fmt.Errorf("parent with hash retrieving error: %w", err)
+		} else if parent == nil {
+			// if block does not exist (for example reorg happened) GetBlockByHash will return nil, nil
 			return nil, -1, fmt.Errorf("parent with hash %s not found", block.ParentHash)
 		}
 

tracker/tracker.go

@@ -314,10 +314,16 @@ func (t *Tracker) findAncestor(block, pivot *ethgo.Block) (uint64, error) {
 		block, err = t.provider.GetBlockByHash(block.ParentHash, false)
 		if err != nil {
 			return 0, err
+		} else if block == nil {
+			// if block does not exist (for example reorg happened) GetBlockByNumber will return nil, nil
+			return 0, fmt.Errorf("block with hash %s not found", block.ParentHash)
 		}
 		pivot, err = t.provider.GetBlockByHash(pivot.ParentHash, false)
 		if err != nil {
 			return 0, err
+		} else if pivot == nil {
+			// if block does not exist (for example reorg happened) GetBlockByNumber will return nil, nil
+			return 0, fmt.Errorf("block/pivot with hash %s not found", pivot.ParentHash)
 		}
 	}
 	return 0, fmt.Errorf("the reorg is bigger than maxBlockBacklog %d", t.blockTracker.MaxBlockBacklog())
@@ -383,7 +389,7 @@ START:
 	t.emitLogs(EventAdd, logs)
 
 	// update the last block entry
-	block, err := t.provider.GetBlockByNumber(ethgo.BlockNumber(dst), false)
+	block, err := t.getBlockByNumber(dst)
 	if err != nil {
 		return err
 	}
@@ -418,7 +424,7 @@ func (t *Tracker) preSyncCheck() error {
 }
 
 func (t *Tracker) preSyncCheckImpl() error {
-	rGenesis, err := t.provider.GetBlockByNumber(0, false)
+	rGenesis, err := t.getBlockByNumber(0)
 	if err != nil {
 		return err
 	}
@@ -456,7 +462,7 @@ func (t *Tracker) preSyncCheckImpl() error {
 func (t *Tracker) fastTrack(filterConfig *FilterConfig) (*ethgo.Block, error) {
 	// Try to use first the user provided block if any
 	if filterConfig.Start != 0 {
-		bb, err := t.provider.GetBlockByNumber(ethgo.BlockNumber(filterConfig.Start), false)
+		bb, err := t.getBlockByNumber(filterConfig.Start)
 		if err != nil {
 			return nil, err
 		}
@@ -518,7 +524,7 @@ func (t *Tracker) fastTrack(filterConfig *FilterConfig) (*ethgo.Block, error) {
 			}
 		}
 
-		bb, err := t.provider.GetBlockByNumber(ethgo.BlockNumber(minBlock-1), false)
+		bb, err := t.getBlockByNumber(minBlock - 1)
 		if err != nil {
 			return nil, err
 		}
@@ -650,7 +656,7 @@ func (t *Tracker) syncImpl(ctx context.Context) error {
 			return fmt.Errorf("store is more advanced than the chain")
 		}
 
-		pivot, err := t.provider.GetBlockByNumber(ethgo.BlockNumber(last.Number), false)
+		pivot, err := t.getBlockByNumber(last.Number)
 		if err != nil {
 			return err
 		}
@@ -674,7 +680,7 @@ func (t *Tracker) syncImpl(ctx context.Context) error {
 			}
 			t.emitLogs(EventDel, logs)
 
-			last, err = t.provider.GetBlockByNumber(ethgo.BlockNumber(ancestor), false)
+			last, err = t.getBlockByNumber(ancestor)
 			if err != nil {
 				return err
 			}
@@ -843,6 +849,18 @@ func (t *Tracker) doFilter(added []*ethgo.Block, removed []*ethgo.Block) (*Event
 	return evnt, nil
 }
 
+func (t *Tracker) getBlockByNumber(blockNumber uint64) (*ethgo.Block, error) {
+	block, err := t.provider.GetBlockByNumber(ethgo.BlockNumber(blockNumber), false)
+	if err != nil {
+		return nil, err
+	} else if block == nil {
+		// if block does not exist (for example reorg happened) GetBlockByNumber will return nil, nil
+		return nil, fmt.Errorf("block with number %d not found", blockNumber)
+	}
+
+	return block, nil
+}
+
 // EventType is the type of the event
 type EventType int