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configuration.md

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Configuration Guide

This guide provides detailed information about configuring Ethers for your Elixir project. We'll cover all available configuration options, their purposes, and best practices for different scenarios.

Json RPC Configuration

Ethers uses Ethereumex as an Ethereum RPC client by default. A default URL can be set using the elixir config statements like the example below.

You can use one of the RPC URLs for your chain/wallet of choice or try out one of them from chainlist.org. We recommend using a reliable RPC provider (line infura or quicknodes) for production.

# Configure the default JSON-RPC endpoint URL
config :ethereumex, url: "https://..."

Note: If your app requires multiple RPC endpoints (e.g. multi-chain) then you need to pass in the URL for each operation via :rpc_opts key. (e.g. Ethers.call(my_fn, rpc_opts: [url: "https://..."])

Configuration Options

RPC Client :rpc_client

Specifies the module responsible for making JSON-RPC calls to the Ethereum node. This module must implement Ethers.RpcClient.Adapter behaviour.

Example

config :ethers, rpc_client: Ethereumex.HttpClient

Keccak Module :keccak_module

Module for Keccak-256 hashing operations. Uses ExKeccak by default.

Example

config :ethers, keccak_module: ExKeccak

JSON Module json_module

Handles JSON encoding/decoding. Uses Jason by default.

Example

config :ethers, json_module: Jason  # If you prefer using Poison

Secp256k1 Module :secp256k1_module

Handles elliptic curve operations for signing and public key operations.

config :ethers, secp256k1_module: ExSecp256k1

Default Signer :default_signer and :default_signer_opts

Specifies the default module for transaction signing by default. Also use default_signer_opts as default signer options if needed (See example).

Built-in Siginers

  • Ethers.Signer.Local: For local private key signing
  • Ethers.Signer.JsonRPC: For remote signing via RPC

Example

config :ethers,
  default_signer: Ethers.Signer.Local,
  default_signer_opts: [private_key: System.fetch_env!("ETH_PRIVATE_KEY")]

Gas Margins

Default Gas Margin :default_gas_margin

Safety margin for gas estimation. Precision is 0.01%. Default is 11000 = 110%.

This will increase the estimated gas value so transactions are less likely to run out of gas.

Example

config :ethers, default_gas_margin: 11000  # 110% gas margin

Max Fee Per Gas Margin :default_max_fee_per_gas_margin

Safety margin for max fee per gas in EIP-1559 transactions. Precision is 0.01%. Default is 12000 = 120%.

config :ethers, default_max_fee_per_gas_margin: 12000  # 120% of current gas price.

Best Practices

  1. Security:

    • Never commit private keys or sensitive configuration
    • Use environment variables for sensitive values
    • Consider using runtime configuration for flexibility

  2. Gas Management:

    • Adjust gas margins based on network conditions
    • Use higher margins on networks with more volatility

  3. RPC Endpoints:

    • Use reliable RPC providers in production
    • Consider fallback RPC endpoints
    • Monitor RPC endpoint performance

  4. Signing:

    • If possible, Use ethers_kms in production for better security
    • Keep private keys secure when using Ethers.Signer.Local

Troubleshooting

Common Issues

  • RPC Connection Issues:
# Verify your RPC connection
config :ethereumex,
  url: "https://your-ethereum-node.com",
  http_options: [recv_timeout: 60_000]  # Increase timeout if needed
  • Gas Estimation Failures: Increase gas margin for complex contracts
config :ethers, default_gas_margin: 15000  # 150%

Or manually provide the gas estimation when sending/signing transactions.