Setting Gas Price on Klaytn Using Ethereum Tools: A Developer's Guide

Introduction

Klaytn's v1.8.0 update brings Ethereum equivalence features, allowing developers to use popular Ethereum tools with minimal modifications. However, unlike Ethereum's dynamic gas pricing, Klaytn uses a fixed gas price model. This guide explains how to properly set gas prices when using Ethereum tools like web3.js, ethers.js, Hardhat, and Truffle on Klaytn.

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Key Ethereum Equivalence Features in Klaytn

• Precompiled Contract Changes: Enhanced compatibility with Ethereum's smart contract environment.
• Ethereum API Support: Full JSON-RPC API support matching Ethereum standards.
• Ethereum Transaction Types: Support for legacy and EIP-1559 transaction formats.

Understanding Gas Price on Klaytn

While Ethereum uses dynamic gas pricing (post EIP-1559), Klaytn maintains fixed gas prices:

• Baobab Testnet: 250 ston
• Cypress Mainnet: 250 ston

Critical Consideration: Ethereum tools generate default gas values based on Ethereum's dynamic model. These defaults will cause transactions to fail on Klaytn. You must explicitly set gas parameters.

Configuring Gas Price in Ethereum Tools

web3.js Implementation

Legacy Transactions:

const tx = await web3.eth.accounts.signTransaction({
  to: recipientAddress,
  value: amount,
  gasPrice: 250000000000, // Explicitly set
  gas: 21000,
}, privateKey);

Dynamic Fee Transactions (EIP-1559):

const tx = await web3.eth.accounts.signTransaction({
  to: recipientAddress,
  value: amount,
  maxFeePerGas: 250000000000, // Both must match Klaytn's fixed price
  maxPriorityFeePerGas: 250000000000,
  gas: 21000,
}, privateKey);

ethers.js Implementation

Legacy Transactions:

const tx = await wallet.sendTransaction({
  to: recipientAddress,
  value: amount,
  gasPrice: 250000000000,
  gasLimit: 21000,
});

Dynamic Fee Transactions:

const tx = await wallet.sendTransaction({
  to: recipientAddress,
  value: amount,
  maxFeePerGas: 250000000000,
  maxPriorityFeePerGas: 250000000000,
  gasLimit: 21000,
});

Development Environment Configuration

Hardhat Setup

Method 1: Configure in hardhat.config.js

module.exports = {
  networks: {
    klaytn: {
      url: "RPC_ENDPOINT",
      gasPrice: 250000000000, // Sets default for all transactions
      accounts: [...]
    }
  }
};

Method 2: Transaction-level Configuration

const contract = await ethers.getContractFactory("Contract");
const deployed = await contract.deploy({
  gasPrice: 250000000000 // Overrides config
});

Truffle Configuration

Legacy Transaction Setup:

module.exports = {
  networks: {
    klaytn: {
      provider: () => new HDWalletProvider(...),
      gasPrice: 250000000000,
      network_id: "*"
    }
  }
};

Dynamic Fee Transaction Setup:

module.exports = {
  networks: {
    klaytn: {
      provider: () => new HDWalletProvider(...),
      maxFeePerGas: 250000000000,
      maxPriorityFeePerGas: 250000000000,
      network_id: "*"
    }
  }
};

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Best Practices and Troubleshooting

1. Migration Contracts: When using Truffle migrations, configure gas prices in truffle-config.js rather than transaction code to ensure consistent behavior.

2. Network Forking: When forking Klaytn nodes:

   • Archive mode: Fork at any block
   • Full mode: Fork at blocks multiples of 128

3. Transaction Failure: If transactions fail:

   • Verify gas price matches current network requirements
   • Check for sufficient gas limits
   • Confirm proper transaction type (legacy vs EIP-1559)

FAQ Section

Q: Why do my Ethereum tool transactions fail on Klaytn?
A: This occurs when tools use Ethereum's dynamic gas pricing defaults. You must explicitly set Klaytn's fixed gas price.

Q: Can I use the same gas price for both legacy and EIP-1559 transactions?
A: Yes, set both gasPrice (legacy) and maxFeePerGas/maxPriorityFeePerGas (EIP-1559) to Klaytn's fixed price.

Q: How do I find Klaytn's current gas price?
A: Check the latest documentation or use the klay_gasPrice RPC call.

Q: Are there any special considerations for migration contracts?
A: Yes, configure gas prices in truffle-config.js rather than transaction code to ensure proper migration contract functionality.

Q: What happens if I set different values for maxFee and maxPriorityFee?
A: On Klaytn, both values should be identical as the network uses fixed pricing.

Conclusion

With Klaytn's Ethereum equivalence features, developers can leverage familiar Ethereum tools while adapting to Klaytn's fixed gas price model. By following this guide's configuration recommendations, you can ensure seamless transaction processing on the Klaytn network.