transaction type not supported. Arbitrum getBlockByNumber. Golang

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04-10-2024

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"Transaction Type Not Supported" Error with Arbitrum getBlockByNumber in Golang: A Deep Dive

Have you encountered the cryptic "Transaction Type Not Supported" error while using the Arbitrum getBlockByNumber function in your Golang application? This error can be frustrating, leaving you scratching your head. Let's break down what causes this error and how to resolve it.

Scenario: The Case of the Unsupported Transactions

Imagine you're building a Golang application that interacts with the Arbitrum blockchain. You need to retrieve specific block data using the getBlockByNumber function from the Arbitrum RPC endpoint. You might be using a library like ethclient or ethereum to facilitate this communication.

Here's a snippet of the typical code you might encounter:

package main

import (
	"context"
	"fmt"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethclient"
)

func main() {
	client, err := ethclient.Dial("https://arb1.arbitrum.io/rpc")
	if err != nil {
		panic(err)
	}

	blockNumber := big.NewInt(100)
	block, err := client.BlockByNumber(context.Background(), blockNumber)
	if err != nil {
		fmt.Println("Error fetching block:", err)
	} else {
		fmt.Println("Block found:", block.Hash())
	}
}

This code snippet demonstrates a basic attempt to retrieve block data using the Arbitrum RPC endpoint. However, it could encounter the "Transaction Type Not Supported" error.

Why the Error? Dissecting the Issue

The root of the problem lies in the type of transaction supported by the Arbitrum RPC endpoint. While Ethereum-based blockchains traditionally use the "EIP-155" transaction type, Arbitrum utilizes a different transaction type. This discrepancy causes the standard getBlockByNumber function (which assumes EIP-155) to fail.

Solutions: Adapting to Arbitrum's Transactions

To overcome this hurdle, you need to adapt your approach to accommodate Arbitrum's transaction type. Here's how you can do it:

1. Leverage the ethclient Library's Custom Functionality:

• The ethclient library allows you to specify a custom transaction type during the block retrieval process. Instead of relying on the default getBlockByNumber, you can use the getBlockByHash function, passing in the block hash (which you can get from the eth_getBlockByNumber RPC call).

package main

import (
	"context"
	"fmt"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethclient"
)

func main() {
	client, err := ethclient.Dial("https://arb1.arbitrum.io/rpc")
	if err != nil {
		panic(err)
	}

	blockNumber := big.NewInt(100)
	// Use eth_getBlockByNumber RPC call to get the block hash 
	blockHash, err := client.CallContext(context.Background(), nil, "eth_getBlockByNumber", blockNumber)
	if err != nil {
		fmt.Println("Error fetching block hash:", err)
		return
	}
	// Use getBlockByHash with the custom transaction type
	block, err := client.BlockByHash(context.Background(), common.HexToHash(blockHash.String()))
	if err != nil {
		fmt.Println("Error fetching block:", err)
	} else {
		fmt.Println("Block found:", block.Hash())
	}
}

2. Implement Custom RPC Call for Block Retrieval:

• If you are not using the ethclient library, or if you prefer more granular control, you can directly make custom RPC calls using libraries like go-ethereum/rpc. This allows you to specify the desired transaction type and parse the response accordingly.

package main

import (
	"context"
	"fmt"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/rpc"
)

func main() {
	client, err := rpc.Dial("https://arb1.arbitrum.io/rpc")
	if err != nil {
		panic(err)
	}

	blockNumber := big.NewInt(100)
	var blockHash common.Hash
	// Use custom RPC call
	err = client.CallContext(context.Background(), &blockHash, "eth_getBlockByNumber", blockNumber)
	if err != nil {
		fmt.Println("Error fetching block hash:", err)
		return
	}

	// Use getBlockByHash with the custom transaction type
	block, err := client.BlockByHash(context.Background(), blockHash)
	if err != nil {
		fmt.Println("Error fetching block:", err)
	} else {
		fmt.Println("Block found:", block.Hash())
	}
}

Key Takeaways

• Understand Arbitrum's Transaction Type: Remember that Arbitrum operates with a different transaction type than traditional Ethereum chains.
• Adapt Your Approach: Adjust your code to accommodate Arbitrum's transaction type by using custom functionality or implementing custom RPC calls.
• Utilize Available Libraries: Libraries like ethclient provide helpful abstractions for working with different blockchains.
• Consult Arbitrum Documentation: Refer to the official Arbitrum documentation for detailed information on their transaction types and API specifications.

By following these guidelines, you can successfully retrieve block data from the Arbitrum blockchain using Golang and navigate the "Transaction Type Not Supported" error.