Crate ethers_middleware

Ethers Middleware

Ethers uses a middleware-based architecture. You start the middleware stack with a Provider, and wrap it with additional middleware functionalities that you need.

Available Middleware

• Signer: Signs transactions locally, with a private key or a hardware wallet
• Nonce Manager: Manages nonces locally, allowing the rapid broadcast of transactions without having to wait for them to be submitted
• Gas Escalator: Bumps transaction gas prices in the background
• Gas Oracle: Allows getting your gas price estimates from places other than eth_gasPrice.
• Transformer: Allows intercepting and transforming a transaction to be broadcasted via a proxy wallet, e.g. DSProxy.

Example of a middleware stack

use ethers_providers::{Provider, Http};
use ethers_signers::{LocalWallet, Signer};
use ethers_middleware::{
    gas_escalator::{GasEscalatorMiddleware, GeometricGasPrice, Frequency},
    gas_oracle::{GasOracleMiddleware, GasNow, GasCategory},
    signer::SignerMiddleware,
    nonce_manager::NonceManagerMiddleware,
};
use ethers_core::rand;
use std::convert::TryFrom;

// Start the stack
let provider = Provider::<Http>::try_from("http://localhost:8545").unwrap();

// Escalate gas prices
let escalator = GeometricGasPrice::new(1.125, 60u64, None::<u64>);
let provider =
    GasEscalatorMiddleware::new(provider, escalator, Frequency::PerBlock);

// Sign transactions with a private key
let signer = LocalWallet::new(&mut rand::thread_rng());
let address = signer.address();
let provider = SignerMiddleware::new(provider, signer);

// Use GasNow as the gas oracle
let gas_oracle = GasNow::new().category(GasCategory::SafeLow);
let provider = GasOracleMiddleware::new(provider, gas_oracle);

// Manage nonces locally
let provider = NonceManagerMiddleware::new(provider, address);

// ... do something with the provider

Re-exports

pub use nonce_manager::NonceManagerMiddleware;

pub use signer::SignerMiddleware;

pub use policy::PolicyMiddleware;

Modules

gas_escalator

The Gas Escalator middleware is used to re-broadcast transactions with an increasing gas price to guarantee their timely inclusion.

gas_oracle

The gas oracle middleware is used to get the gas price from a list of gas oracles instead of using eth_gasPrice. For usage examples, refer to the GasOracle trait.

nonce_manager

The Nonce Manager is used to locally calculate nonces instead of using eth_getTransactionCount

policy

The Policy is used to ensure transactions comply with the rules configured in the PolicyMiddleware before sending them.

signer

The Signer is used to locally sign transactions and messages instead of using eth_sendTransaction and eth_sign

transformer

The Transformer is used to intercept transactions and transform them to be sent via various supported transformers, e.g., DSProxy