From 979f210828cc5aba2ce1b202d37d3b3a8335b6dd Mon Sep 17 00:00:00 2001
From: Jeffery Walsh <cyberhorsey@gmail.com>
Date: Tue, 20 Jun 2023 13:52:13 -0700
Subject: [PATCH] error handling

---
 packages/relayer/message/errors.go          | 28 +++++++++++++++++++++
 packages/relayer/message/process_message.go | 14 +++++++----
 2 files changed, 37 insertions(+), 5 deletions(-)
 create mode 100644 packages/relayer/message/errors.go

diff --git a/packages/relayer/message/errors.go b/packages/relayer/message/errors.go
new file mode 100644
index 00000000000..0bf2d406aeb
--- /dev/null
+++ b/packages/relayer/message/errors.go
@@ -0,0 +1,28 @@
+package message
+
+import (
+	"math/big"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+var (
+	//lint:ignore ST1005 allow `errMaxPriorityFeePerGasNotFound` to be capitalized.
+	errMaxPriorityFeePerGasNotFound = errors.New(
+		"Method eth_maxPriorityFeePerGas not found",
+	)
+
+	// FallbackGasTipCap is the default fallback gasTipCap used when we are
+	// unable to query an L1 backend for a suggested gasTipCap.
+	FallbackGasTipCap = big.NewInt(1500000000)
+)
+
+// IsMaxPriorityFeePerGasNotFoundError returns true if the provided error
+// signals that the backend does not support the eth_maxPrirorityFeePerGas
+// method. In this case, the caller should fallback to using the constant above.
+func IsMaxPriorityFeePerGasNotFoundError(err error) bool {
+	return strings.Contains(
+		err.Error(), errMaxPriorityFeePerGasNotFound.Error(),
+	)
+}
diff --git a/packages/relayer/message/process_message.go b/packages/relayer/message/process_message.go
index 6f5b635f7b2..b6b426fcb55 100644
--- a/packages/relayer/message/process_message.go
+++ b/packages/relayer/message/process_message.go
@@ -207,12 +207,16 @@ func (p *Processor) sendProcessMessageCall(
 
 	gasTipCap, err := p.destEthClient.SuggestGasTipCap(ctx)
 	if err != nil {
-		gasPrice, err := p.destEthClient.SuggestGasPrice(context.Background())
-		if err != nil {
-			return nil, errors.Wrap(err, "p.destBridge.SuggestGasPrice")
-		}
+		if IsMaxPriorityFeePerGasNotFoundError(err) {
+			auth.GasTipCap = FallbackGasTipCap
+		} else {
+			gasPrice, err := p.destEthClient.SuggestGasPrice(context.Background())
+			if err != nil {
+				return nil, errors.Wrap(err, "p.destBridge.SuggestGasPrice")
+			}
 
-		auth.GasPrice = gasPrice
+			auth.GasPrice = gasPrice
+		}
 	} else {
 		auth.GasTipCap = gasTipCap
 	}