From 015b0ac8613741da346d8e7852c89f38da22cce7 Mon Sep 17 00:00:00 2001
From: lbqds <lbqds@outlook.com>
Date: Fri, 15 Mar 2024 14:11:18 +0800
Subject: [PATCH] Retrieve the latest event index from the database when
 restarting

---
 explorer-backend/main.go             | 14 ++------------
 explorer-backend/transactions/evm.go | 16 +++++++++++-----
 2 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/explorer-backend/main.go b/explorer-backend/main.go
index d693ca55..a1d5206d 100644
--- a/explorer-backend/main.go
+++ b/explorer-backend/main.go
@@ -346,18 +346,13 @@ func run(cmd *cobra.Command, args []string) {
 			return err
 		}
 
-		ethEventIndex, err := watcher.GetLatestEventIndexEth(ctx)
-		if err != nil {
-			logger.Error("failed to get latest event index", zap.Uint16("chainId", uint16(vaa.ChainIDEthereum)), zap.Error(err))
-			return err
-		}
 		ethWatcher, err := transactions.NewEVMWatcher(
 			logger,
 			ctx,
 			*ethRpcUrl,
 			vaa.ChainIDEthereum,
 			bridgeConfig.Ethereum,
-			*ethEventIndex,
+			watcher.GetLatestEventIndexEth,
 			blockTxsC,
 		)
 		if err != nil {
@@ -369,18 +364,13 @@ func run(cmd *cobra.Command, args []string) {
 		}
 
 		if *bscRpcUrl != "" && *network == "devnet" {
-			bscEventIndex, err := watcher.GetLatestEventIndexBsc(ctx)
-			if err != nil {
-				logger.Error("failed to get latest event index", zap.Uint16("chainId", uint16(vaa.ChainIDBSC)), zap.Error(err))
-				return err
-			}
 			bscWatcher, err := transactions.NewEVMWatcher(
 				logger,
 				ctx,
 				*bscRpcUrl,
 				vaa.ChainIDBSC,
 				bridgeConfig.Bsc,
-				*bscEventIndex,
+				watcher.GetLatestEventIndexBsc,
 				blockTxsC,
 			)
 			if err != nil {
diff --git a/explorer-backend/transactions/evm.go b/explorer-backend/transactions/evm.go
index 967f92f1..8d95baa4 100644
--- a/explorer-backend/transactions/evm.go
+++ b/explorer-backend/transactions/evm.go
@@ -23,7 +23,7 @@ type EVMWatcher struct {
 	chainConfig     *common.ChainConfig
 	connector       *ethereum.EthereumConnector
 	contractAddress *ethCommon.Address
-	fromHeight      uint32
+	getEventIndex   func(context.Context) (*uint32, error)
 	blockTxsC       chan<- []*BlockTransactions
 	logger          *zap.Logger
 }
@@ -34,7 +34,7 @@ func NewEVMWatcher(
 	rpcUrl string,
 	chainId vaa.ChainID,
 	chainConfig *common.ChainConfig,
-	fromHeight uint32,
+	getEventIndex func(context.Context) (*uint32, error),
 	blockTxsC chan<- []*BlockTransactions,
 ) (*EVMWatcher, error) {
 	contractAddress := ethCommon.HexToAddress(chainConfig.Contracts.Governance)
@@ -48,7 +48,7 @@ func NewEVMWatcher(
 		chainConfig:     chainConfig,
 		contractAddress: &contractAddress,
 		connector:       connector,
-		fromHeight:      fromHeight,
+		getEventIndex:   getEventIndex,
 		blockTxsC:       blockTxsC,
 		logger:          namedLogger,
 	}, nil
@@ -69,7 +69,13 @@ func (w *EVMWatcher) Run() func(ctx context.Context) error {
 }
 
 func (w *EVMWatcher) fetchEvents(ctx context.Context, errC chan<- error) {
-	w.logger.Info("evm watcher started", zap.Uint32("fromHeight", w.fromHeight))
+	fromHeight, err := w.getEventIndex(ctx)
+	if err != nil {
+		w.logger.Error("failed to get latest event index", zap.Error(err), zap.Uint16("chainId", uint16(w.chainId)))
+		errC <- err
+		return
+	}
+	w.logger.Info("evm watcher started", zap.Uint32("fromHeight", *fromHeight))
 
 	blockC := make(chan *ethereum.NewBlock, 64)
 	subscription, err := w.connector.SubscribeForBlocks(ctx, blockC)
@@ -92,7 +98,7 @@ func (w *EVMWatcher) fetchEvents(ctx context.Context, errC chan<- error) {
 			w.logger.Info("received new block", zap.Uint64("height", block.Number.Uint64()), zap.String("hash", block.Hash.Hex()))
 			if isFirstBlock {
 				isFirstBlock = false
-				if err := w.fetchEventsFromBlockRange(ctx, w.fromHeight, uint32(block.Number.Uint64())); err != nil {
+				if err := w.fetchEventsFromBlockRange(ctx, *fromHeight, uint32(block.Number.Uint64())); err != nil {
 					w.logger.Error("failed to fetch events by block range", zap.Error(err))
 					errC <- err
 					return