fix: removed maxHeightDiff to let observer scan Bitcoin block from where it left off (#2222)

* removed maxHeightDiff to let observer scan Bitcoin block from where it left off

* added changelog entry

* renamed LoadLastBlock -> LoadLastScannedBlock; added more comments

* run format

---------

Co-authored-by: Lucas Bertrand <[email protected]>

Author: ws4charlie

changelog.md

@@ -40,6 +40,7 @@
 
 * [1484](https://github.com/zeta-chain/node/issues/1484) - replaced hard-coded `MaxLookaheadNonce` with a default lookback factor
 * [2125](https://github.com/zeta-chain/node/pull/2125) - fix develop upgrade test
+* [2222](https://github.com/zeta-chain/node/pull/2222) - removed `maxHeightDiff` to let observer scan from Bitcoin height where it left off
 
 ### CI
 

zetaclient/chains/bitcoin/observer/observer.go

@@ -39,9 +39,6 @@ import (
 )
 
 const (
-	// maxHeightDiff contains the max height diff in case the last block is too old when the observer starts
-	maxHeightDiff = 10000
-
 	// btcBlocksPerDay represents Bitcoin blocks per days for LRU block cache size
 	btcBlocksPerDay = 144
 
@@ -684,37 +681,35 @@ func (ob *Observer) BuildBroadcastedTxMap() error {
 	return nil
 }
 
-func (ob *Observer) LoadLastBlock() error {
+// LoadLastScannedBlock loads last scanned block from database
+// The last scanned block is the height from which the observer should continue scanning for inbound transactions
+func (ob *Observer) LoadLastScannedBlock() error {
 	// Get the latest block number from node
 	bn, err := ob.rpcClient.GetBlockCount()
 	if err != nil {
 		return err
 	}
 	if bn < 0 {
-		return fmt.Errorf("LoadLastBlock: negative block number %d", bn)
+		return fmt.Errorf("LoadLastScannedBlock: negative block number %d", bn)
 	}
 
 	//Load persisted block number
 	var lastBlockNum clienttypes.LastBlockSQLType
 	if err := ob.db.First(&lastBlockNum, clienttypes.LastBlockNumID).Error; err != nil {
-		ob.logger.Chain.Info().Msg("LastBlockNum not found in DB, scan from latest")
+		ob.logger.Chain.Info().Msg("LoadLastScannedBlock: last scanned block not found in DB, scan from latest")
 		ob.SetLastBlockHeightScanned(bn)
 	} else {
 		// #nosec G701 always in range
 		lastBN := int64(lastBlockNum.Num)
 		ob.SetLastBlockHeightScanned(lastBN)
-
-		//If persisted block number is too low, use the latest height
-		if (bn - lastBN) > maxHeightDiff {
-			ob.logger.Chain.Info().Msgf("LastBlockNum too low: %d, scan from latest", lastBlockNum.Num)
-			ob.SetLastBlockHeightScanned(bn)
-		}
 	}
 
-	if ob.chain.ChainId == 18444 { // bitcoin regtest: start from block 100
+	// bitcoin regtest starts from block 100
+	if chains.IsBitcoinRegnet(ob.chain.ChainId) {
 		ob.SetLastBlockHeightScanned(100)
 	}
-	ob.logger.Chain.Info().Msgf("%s: start scanning from block %d", ob.chain.String(), ob.GetLastBlockHeightScanned())
+	ob.logger.Chain.Info().
+		Msgf("LoadLastScannedBlock: chain %d starts scanning from block %d", ob.chain.ChainId, ob.GetLastBlockHeightScanned())
 
 	return nil
 }
@@ -812,8 +807,8 @@ func (ob *Observer) loadDB(dbpath string) error {
 		return err
 	}
 
-	//Load last block
-	err = ob.LoadLastBlock()
+	// Load last scanned block
+	err = ob.LoadLastScannedBlock()
 	if err != nil {
 		return err
 	}

zetaclient/chains/evm/observer/observer.go

@@ -570,12 +570,17 @@ func (ob *Observer) BlockByNumber(blockNumber int) (*ethrpc.Block, error) {
 	return block, nil
 }
 
-func (ob *Observer) BuildLastBlock() error {
-	logger := ob.logger.Chain.With().Str("module", "BuildBlockIndex").Logger()
+// LoadLastScannedBlock loads last scanned block from specified height or from database
+// The last scanned block is the height from which the observer should continue scanning for inbound transactions
+func (ob *Observer) LoadLastScannedBlock() error {
+	// get environment variable
 	envvar := ob.chain.ChainName.String() + "_SCAN_FROM"
 	scanFromBlock := os.Getenv(envvar)
+
+	// load from environment variable if set
 	if scanFromBlock != "" {
-		logger.Info().Msgf("BuildLastBlock: envvar %s is set; scan from  block %s", envvar, scanFromBlock)
+		ob.logger.Chain.Info().
+			Msgf("LoadLastScannedBlock: envvar %s is set; scan from  block %s", envvar, scanFromBlock)
 		if scanFromBlock == clienttypes.EnvVarLatest {
 			header, err := ob.evmClient.HeaderByNumber(context.Background(), nil)
 			if err != nil {
@@ -589,22 +594,26 @@ func (ob *Observer) BuildLastBlock() error {
 			}
 			ob.SetLastBlockHeightScanned(scanFromBlockInt)
 		}
-	} else { // last observed block
-		var lastBlockNum clienttypes.LastBlockSQLType
-		if err := ob.db.First(&lastBlockNum, clienttypes.LastBlockNumID).Error; err != nil {
-			logger.Info().Msgf("BuildLastBlock: db PosKey does not exist; read from external chain %s", ob.chain.String())
+	} else {
+		// load from DB otherwise
+		var lastBlock clienttypes.LastBlockSQLType
+		if err := ob.db.First(&lastBlock, clienttypes.LastBlockNumID).Error; err != nil {
+			ob.logger.Chain.Info().Msg("LoadLastScannedBlock: last scanned block not found in DB, scan from latest")
 			header, err := ob.evmClient.HeaderByNumber(context.Background(), nil)
 			if err != nil {
 				return err
 			}
 			ob.SetLastBlockHeightScanned(header.Number.Uint64())
 			if dbc := ob.db.Save(clienttypes.ToLastBlockSQLType(ob.GetLastBlockHeightScanned())); dbc.Error != nil {
-				logger.Error().Err(dbc.Error).Msgf("BuildLastBlock: error writing lastBlockScanned %d to db", ob.GetLastBlockHeightScanned())
+				ob.logger.Chain.Error().Err(dbc.Error).Msgf("LoadLastScannedBlock: error writing last scanned block %d to DB", ob.GetLastBlockHeightScanned())
 			}
 		} else {
-			ob.SetLastBlockHeightScanned(lastBlockNum.Num)
+			ob.SetLastBlockHeightScanned(lastBlock.Num)
 		}
 	}
+	ob.logger.Chain.Info().
+		Msgf("LoadLastScannedBlock: chain %d starts scanning from block %d", ob.chain.ChainId, ob.GetLastBlockHeightScanned())
+
 	return nil
 }
 
@@ -635,7 +644,7 @@ func (ob *Observer) LoadDB(dbPath string, chain chains.Chain) error {
 		}
 
 		ob.db = db
-		err = ob.BuildLastBlock()
+		err = ob.LoadLastScannedBlock()
 		if err != nil {
 			return err
 		}