feat(relayer): Wait N confirmations on source chain before processing message on destination chain

packages/relayer/.default.env

@@ -7,4 +7,5 @@ RELAYER_ECDSA_KEY=
 L1_BRIDGE_ADDRESS=0xa566811E9E63e4F573Df89d5453bB89F239F7e10
 L2_BRIDGE_ADDRESS=0xa566811E9E63e4F573Df89d5453bB89F239F7e10
 L1_RPC_URL="wss://eth-goerli.g.alchemy.com/v2/bPAA5rQ42Zoo4ts9TYnTB2t0cuc5lf7_"
-L2_RPC_URL="wss://rinkeby-light.eth.linkpool.io/ws"
+L2_RPC_URL="wss://rinkeby-light.eth.linkpool.io/ws"
+CONFIRMATIONS_BEFORE_PROCESSING=15

packages/relayer/.golangci.yml

@@ -25,7 +25,7 @@ linters:
 
 linters-settings:
   funlen:
-    lines: 100
+    lines: 105
     statements: 45
   gocognit:
     min-complexity: 32

packages/relayer/cli/cli.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"strconv"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/rpc"
@@ -32,7 +33,10 @@ var (
 		"MYSQL_DATABASE",
 		"MYSQL_HOST",
 		"RELAYER_ECDSA_KEY",
+		"CONFIRMATIONS_BEFORE_PROCESSING",
 	}
+
+	defaultConfirmations = 15
 )
 
 func Run(mode relayer.Mode, layer relayer.Layer) {
@@ -107,6 +111,11 @@ func makeIndexers(layer relayer.Layer, db *gorm.DB) ([]*indexer.Service, func(),
 		return nil, nil, err
 	}
 
+	confirmations, err := strconv.Atoi(os.Getenv("CONFIRMATIONS_BEFORE_PROCESSING"))
+	if err != nil || confirmations <= 0 {
+		confirmations = defaultConfirmations
+	}
+
 	indexers := make([]*indexer.Service, 0)
 
 	if layer == relayer.L1 || layer == relayer.Both {
@@ -122,6 +131,8 @@ func makeIndexers(layer relayer.Layer, db *gorm.DB) ([]*indexer.Service, func(),
 			BridgeAddress:     common.HexToAddress(os.Getenv("L1_BRIDGE_ADDRESS")),
 			DestBridgeAddress: common.HexToAddress(os.Getenv("L2_BRIDGE_ADDRESS")),
 			DestTaikoAddress:  common.HexToAddress(os.Getenv("L2_TAIKO_ADDRESS")),
+
+			Confirmations: uint64(confirmations),
 		})
 		if err != nil {
 			log.Fatal(err)
@@ -143,6 +154,8 @@ func makeIndexers(layer relayer.Layer, db *gorm.DB) ([]*indexer.Service, func(),
 			BridgeAddress:     common.HexToAddress(os.Getenv("L2_BRIDGE_ADDRESS")),
 			DestBridgeAddress: common.HexToAddress(os.Getenv("L1_BRIDGE_ADDRESS")),
 			DestTaikoAddress:  common.HexToAddress(os.Getenv("L1_TAIKO_ADDRESS")),
+
+			Confirmations: uint64(confirmations),
 		})
 		if err != nil {
 			log.Fatal(err)

packages/relayer/errors.go

@@ -15,5 +15,10 @@ var (
 	ErrNoRPCClient = errors.Validation.NewWithKeyAndDetail("ERR_NO_RPC_CLIENT", "RPCClient is required")
 	ErrNoBridge    = errors.Validation.NewWithKeyAndDetail("ERR_NO_BRIDGE", "Bridge is required")
 	ErrNoTaikoL2   = errors.Validation.NewWithKeyAndDetail("ERR_NO_TAIKO_L2", "TaikoL2 is required")
+
+	ErrInvalidConfirmations = errors.Validation.NewWithKeyAndDetail(
+		"ERR_INVALID_CONFIRMATIONS",
+		"Confirmations amount is invalid, must be numerical and > 0",
+	)
 	ErrInvalidMode = errors.Validation.NewWithKeyAndDetail("ERR_INVALID_MODE", "Mode not supported")
 )

packages/relayer/indexer/service.go

@@ -53,6 +53,7 @@ type NewServiceOpts struct {
 	BridgeAddress     common.Address
 	DestBridgeAddress common.Address
 	DestTaikoAddress  common.Address
+	Confirmations     uint64
 }
 
 func NewService(opts NewServiceOpts) (*Service, error) {
@@ -130,6 +131,8 @@ func NewService(opts NewServiceOpts) (*Service, error) {
 		DestBridge:       destBridge,
 		EventRepo:        opts.EventRepo,
 		DestHeaderSyncer: destHeaderSyncer,
+		Confirmations:    opts.Confirmations,
+		SrcETHClient:     opts.EthClient,
 	})
 	if err != nil {
 		return nil, errors.Wrap(err, "message.NewProcessor")

packages/relayer/indexer/service_test.go

@@ -40,6 +40,7 @@ func Test_NewService(t *testing.T) {
 				ECDSAKey:          dummyEcdsaKey,
 				BridgeAddress:     common.HexToAddress(dummyAddress),
 				DestBridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations:     1,
 			},
 			nil,
 		},
@@ -53,6 +54,7 @@ func Test_NewService(t *testing.T) {
 				ECDSAKey:          dummyEcdsaKey,
 				BridgeAddress:     common.HexToAddress(dummyAddress),
 				DestBridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations:     1,
 			},
 			relayer.ErrNoRPCClient,
 		},
@@ -66,6 +68,7 @@ func Test_NewService(t *testing.T) {
 				ECDSAKey:          dummyEcdsaKey,
 				RPCClient:         &rpc.Client{},
 				DestBridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations:     1,
 			},
 			relayer.ErrNoBridgeAddress,
 		},
@@ -79,6 +82,7 @@ func Test_NewService(t *testing.T) {
 				ECDSAKey:      dummyEcdsaKey,
 				RPCClient:     &rpc.Client{},
 				BridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations: 1,
 			},
 			relayer.ErrNoBridgeAddress,
 		},
@@ -92,6 +96,7 @@ func Test_NewService(t *testing.T) {
 				DestEthClient:     &ethclient.Client{},
 				BridgeAddress:     common.HexToAddress(dummyAddress),
 				DestBridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations:     1,
 			},
 			relayer.ErrNoECDSAKey,
 		},
@@ -105,6 +110,7 @@ func Test_NewService(t *testing.T) {
 				BridgeAddress:     common.HexToAddress(dummyAddress),
 				RPCClient:         &rpc.Client{},
 				DestBridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations:     1,
 			},
 			relayer.ErrNoEventRepository,
 		},
@@ -118,6 +124,7 @@ func Test_NewService(t *testing.T) {
 				DestEthClient:     &ethclient.Client{},
 				BridgeAddress:     common.HexToAddress(dummyAddress),
 				DestBridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations:     1,
 			},
 			relayer.ErrNoBlockRepository,
 		},
@@ -131,6 +138,7 @@ func Test_NewService(t *testing.T) {
 				DestEthClient:     &ethclient.Client{},
 				BridgeAddress:     common.HexToAddress(dummyAddress),
 				DestBridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations:     1,
 			},
 			relayer.ErrNoEthClient,
 		},
@@ -144,6 +152,7 @@ func Test_NewService(t *testing.T) {
 				RPCClient:         &rpc.Client{},
 				BridgeAddress:     common.HexToAddress(dummyAddress),
 				DestBridgeAddress: common.HexToAddress(dummyAddress),
+				Confirmations:     1,
 			},
 			relayer.ErrNoEthClient,
 		},

packages/relayer/message/process_message.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/hex"
 	"math/big"
+	"time"
 
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
@@ -29,6 +30,10 @@ func (p *Processor) ProcessMessage(
 		return errors.New("only user can process this, gasLimit set to 0")
 	}
 
+	if err := p.waitForConfirmations(ctx, event.Raw.TxHash, event.Raw.BlockNumber); err != nil {
+		return errors.Wrap(err, "p.waitForConfirmations")
+	}
+
 	// get latest synced header since not every header is synced from L1 => L2,
 	// and later blocks still have the storage trie proof from previous blocks.
 	latestSyncedHeader, err := p.destHeaderSyncer.GetLatestSyncedHeader(&bind.CallOpts{})
@@ -116,3 +121,21 @@ func (p *Processor) ProcessMessage(
 
 	return nil
 }
+
+func (p *Processor) waitForConfirmations(ctx context.Context, txHash common.Hash, blockNumber uint64) error {
+	// TODO: make timeout a config var
+	ctx, cancelFunc := context.WithTimeout(ctx, 2*time.Minute)
+
+	defer cancelFunc()
+
+	if err := relayer.WaitConfirmations(
+		ctx,
+		p.srcEthClient,
+		p.confirmations,
+		txHash,
+	); err != nil {
+		return errors.Wrap(err, "relayer.WaitConfirmations")
+	}
+
+	return nil
+}

packages/relayer/message/processor.go

@@ -13,6 +13,7 @@ import (
 
 type Processor struct {
 	eventRepo     relayer.EventRepository
+	srcEthClient  *ethclient.Client
 	destEthClient *ethclient.Client
 	rpc           *rpc.Client
 	ecdsaKey      *ecdsa.PrivateKey
@@ -21,16 +22,20 @@ type Processor struct {
 	destHeaderSyncer *contracts.IHeaderSync
 
 	prover *proof.Prover
+
+	confirmations uint64
 }
 
 type NewProcessorOpts struct {
 	Prover           *proof.Prover
 	ECDSAKey         *ecdsa.PrivateKey
 	RPCClient        *rpc.Client
+	SrcETHClient     *ethclient.Client
 	DestETHClient    *ethclient.Client
 	DestBridge       *contracts.Bridge
 	EventRepo        relayer.EventRepository
 	DestHeaderSyncer *contracts.IHeaderSync
+	Confirmations    uint64
 }
 
 func NewProcessor(opts NewProcessorOpts) (*Processor, error) {
@@ -50,6 +55,10 @@ func NewProcessor(opts NewProcessorOpts) (*Processor, error) {
 		return nil, relayer.ErrNoEthClient
 	}
 
+	if opts.SrcETHClient == nil {
+		return nil, relayer.ErrNoEthClient
+	}
+
 	if opts.DestBridge == nil {
 		return nil, relayer.ErrNoBridge
 	}
@@ -62,13 +71,22 @@ func NewProcessor(opts NewProcessorOpts) (*Processor, error) {
 		return nil, relayer.ErrNoTaikoL2
 	}
 
+	if opts.Confirmations == 0 {
+		return nil, relayer.ErrInvalidConfirmations
+	}
+
 	return &Processor{
-		eventRepo:        opts.EventRepo,
-		prover:           opts.Prover,
-		ecdsaKey:         opts.ECDSAKey,
-		rpc:              opts.RPCClient,
+		eventRepo: opts.EventRepo,
+		prover:    opts.Prover,
+		ecdsaKey:  opts.ECDSAKey,
+		rpc:       opts.RPCClient,
+
+		srcEthClient: opts.SrcETHClient,
+
 		destEthClient:    opts.DestETHClient,
 		destBridge:       opts.DestBridge,
 		destHeaderSyncer: opts.DestHeaderSyncer,
+
+		confirmations: opts.Confirmations,
 	}, nil
 }