fix: truncate last 255 chars of failure_reason

cmd/bot/run.go

@@ -115,7 +115,7 @@ func ProcessUnprovenBotDelegatedWithdrawals(ctx context.Context, log log.Logger,
 				return
 			} else if strings.Contains(err.Error(), "execution reverted") {
 				// Proven transaction reverted, mark it with the failure reason
-				result := db.Model(&unproven).Update("failure_reason", err.Error())
+				result := db.Model(&unproven).Update("failure_reason", truncFailureReason(err.Error()))
 				if result.Error != nil {
 					log.Error("failed to update failure reason of l2_contract_events", "error", result.Error)
 				}
@@ -154,7 +154,7 @@ func ProcessUnfinalizedBotDelegatedWithdrawals(ctx context.Context, log log.Logg
 				continue
 			} else if strings.Contains(err.Error(), "execution reverted") {
 				// Finalized transaction reverted, mark it with the failure reason
-				result := db.Model(&unfinalized).Update("failure_reason", err.Error())
+				result := db.Model(&unfinalized).Update("failure_reason", truncFailureReason(err.Error()))
 				if result.Error != nil {
 					log.Error("failed to update failure reason of l2_contract_events", "error", result.Error)
 				}
@@ -330,3 +330,14 @@ func queryL2ScannedBlock(db *gorm.DB, cfg *core.Config) (*core.L2ScannedBlock, e
 	}
 	return &l2ScannedBlock, nil
 }
+
+// NOTE: types.L2ContractEvent.FailureReason is defined as `type:varchar(256)` in database.
+func truncFailureReason(reason string) string {
+	const maxFailureReasonLength = 255
+
+	if len(reason) < maxFailureReasonLength {
+		return reason
+	} else {
+		return reason[len(reason)-maxFailureReasonLength:]
+	}
+}