Dynamic RPC proxy

Proxy requests to different Ethereum RPC servers and optionally alter the request.

Usage

1. Run npm install to install dependencies.
2. Copy config.js.example to config.js and edit it to your needs. See below for details.
3. Run npm start to run the proxy.

Configuration

Port

The port key defines the port number the proxy should listen on.

RPCs

The rpcs key defines the list of upstream RPC servers. The rpcs is an object with keys being the name of the RPC and the value being the URL.

Fallback

The fallback key defines the fallback RPC to use if none of the rules matched.

Rules

Each rule is an object with the following properties:

matchers:

Matchers are functions that take three parameters (httpMethod, headers, body) and return a boolean. They are used to match requests to rules. The matchers will be called in the order the rules are defined. Only the first matching rule will be used..

actions:

Actions are used to modify requests before they are sent to the RPC. An action is a function that takes three parameters (httpMethod, headers, body) and returns an object { method, headers, body } with the modified request.

rpc:

The name of the RPC to proxy to if the rule matched. The RPC must be defined in the rpcs section.

Example config: send transactions to Flashbots Protect RPC

const matchers = require('./src/matchers');
const actions = require('./src/actions');

module.exports = {
  port: 8545,
  rpcs: {
    infura: 'https://mainnet.infura.io/v3/9aa3d95b3bc440fa88ea12eaa4456161',
    flashbots: 'https://rpc.flashbots.net',
  },
  fallback: 'infura',
  rules: [
    { matcher: matchers.isRawTx, action: actions.identity, rpc: 'flashbots' },
    { matcher: matchers.any, action: actions.identity, rpc: 'infura' },
  ],
};

This configuration will send all requests to infura except for raw transactions, which will be sent to flashbots. This provides transparently private transactions while avoiding spamming flashbots protect rpc with requests. This was the main motivation and goal of the project.

Example config: send transactions to Flashbots relay

const matchers = require('./src/matchers');
const actions = require('./src/actions');

module.exports = {
  port: 8545,
  rpcs: {
    infura: 'https://mainnet.infura.io/v3/9aa3d95b3bc440fa88ea12eaa4456161',
    flashbots: 'https://relay.flashbots.net',
  },
  fallback: 'infura',
  rules: [
    { matcher: matchers.isRawTx, action: actions.makeTxPrivate, rpc: 'flashbots' },
    { matcher: matchers.any, action: actions.identity, rpc: 'infura' },
  ],
};

This configuration will send all requests to infura except for raw transactions, which will be sent to flashbots and will be made private by changing the rpc method from eth_sendRawTransaction to eth_sendPrivateTransaction.

Heads up: Currently the makeTxPrivate lacks X-Flashbots-Signature header implementation.

License

MIT