Neutrofill

Neutrofill is an automated filler bot that processes inbound transaction requests from CompactX and executes them if deemed profitable. It maintains a server-side wallet and automatically submits transactions that meet profitability criteria.

Features

• Accepts inbound POST requests for transaction execution
• Real-time ETH price monitoring across multiple chains via CoinGecko
• Profitability analysis before transaction submission
• Support for multiple chains (Ethereum, Optimism, Base, Unichain)
• WebSocket support for real-time transaction status updates
• Automated cross-chain token rebalancing via bridging using the Across Protocol
• Automated single-chain token rebalancing via swaps using the Uniswap API

A hosted version can be accessed at neutrofill.com — note that this service is meant to serve as a reference for demonstration purposes and no guarantees about its uptime or reliability are provided.

This project is mostly meant to serve as a starting point until more mature standards like the Open Intents Framework have fully integrated with The Compact.

Getting Started

Prerequisites

• Node.js 18+
• npm 9+

Installation

1. Clone the repository:

   git clone https://github.com/Uniswap/Neutrofill.git
   cd Neutrofill

2. Install dependencies:

   npm install

3. Set up Git hooks:

   npx husky init

4. Copy .env.example to .env and configure your environment:

   cp .env.example .env

Development

• Start the development server with hot reload:

  npm run dev

• Run type checking:

  npm run typecheck

• Run the test suite:

  npm test

• Format and lint code:

  npm run fix

Building

Build both server and client:

npm run build

This will:

• Compile TypeScript server code to dist/server/
• Build React client to dist/client/

Production

Start the production server in production mode:

npm start

Or start the production server with debug logs enabled:

npm run start:debug

Cross-Chain Token Rebalancing

Neutrofill includes an automated cross-chain token rebalancing mechanism that helps maintain target token percentages across multiple blockchain networks. This maintatins sufficient funds on each supported chain to operate efficiently.

Rebalancing Features

• Configurable target percentages for each chain
• Token-specific rebalancing priorities
• Automatic detection of chains that need funds
• Cooldown periods between rebalancing operations
• Minimum and maximum rebalance amounts
• Transaction tracking and status monitoring
• Event-based notifications for rebalance operations

How It Works

For cross-chain bridging:

1. The system monitors token balances across all supported chains
2. When a chain's balance falls below its configured threshold, a rebalance operation is triggered
3. The system identifies a source chain with excess funds
4. Funds are transferred from the source chain to the destination chain using the Across Protocol
5. The operation is tracked until completion

For single-chain swapping, neutrofill uses the Uniswap API. Note that all swaps are performed on Unichain to allow for best execution with lowg gas costs.

Configuration

Rebalancing is configured in src/server/config/rebalance.ts. You can customize:

• Target percentage for each chain / token
• Trigger thresholds for rebalancing
• Token priorities for rebalancing
• Global settings like minimum/maximum amounts and cooldown periods

Configuration

The following environment variables are required:

• PORT: Server port (default: 3000)
• PRIVATE_KEY: Private key for the wallet that will execute transactions
• RPC_URL_MAINNET: Ethereum mainnet RPC URL
• RPC_URL_OPTIMISM: Optimism RPC URL
• RPC_URL_BASE: Base RPC URL
• RPC_URL_UNICHAIN: Unichain RPC URL
• COINGECKO_API_KEY: CoinGecko API key
• UNISWAP_API_KEY: Uniswap API key
• COMPACT_INDEXER: Graphql indexing service (e.g. Ponder node) for The Compact

Supported Networks

• Mainnet (Chain ID: 1)
• Optimism (Chain ID: 10)
• Base (Chain ID: 8453)
• Unichain (Chain ID: 130)

API Endpoints

POST /broadcast

Submit a transaction for potential execution. Generally, this will be relayed from a service like disseminator — reach out to be added as a webhook.

Request body must conform to the BroadcastRequest schema which includes:

• chainId: Chain ID where the resource lock resides (numeric string or hex)
• compact: Compact message object
  • arbiter: Ethereum address
  • sponsor: Ethereum address
  • nonce: 32-byte hex string
  • expires: Numeric string or hex
  • id: Numeric string or hex
  • amount: Numeric string or hex
  • mandate: Mandate object
• sponsorSignature: 64-byte hex string, '0x', or null (no signature indicates an onchain registration)
• allocatorSignature: 64-byte hex string
• context: Context object
  • dispensation: Numeric string or hex
  • dispensationUSD: String (can include $ prefix)
  • spotOutputAmount: Numeric string or hex
  • quoteOutputAmountDirect: Numeric string or hex
  • quoteOutputAmountNet: Numeric string or hex
  • deltaAmount: (optional) Numeric string or hex (can be negative)
  • slippageBips: (optional) Number between 0-10000
  • witnessTypeString: String
  • witnessHash: 32-byte hex string
  • claimHash: (optional) 32-byte hex string
• claimHash: (optional) 32-byte hex string

The mandate object represents parameters related to the fill chain and contains:

• chainId: Chain ID where the resource lock resides (positive number)
• tribunal: Ethereum address
• recipient: Ethereum address
• expires: Numeric string or hex
• token: Ethereum address
• minimumAmount: Numeric string or hex
• baselinePriorityFee: Numeric string or hex
• scalingFactor: Numeric string or hex
• salt: 32-byte hex string

Be sure that any ECDSA signatures are encoded in their "compact" representation using EIP-2098.

GET /health

Check server health status.

Response:

{
  status: "ok",
  timestamp: number  // Unix timestamp in seconds
}

WebSocket Connection

Connect to /ws for real-time transaction status updates. Note: WebSocket endpoint does not support CORS - connections must originate from the same origin.

Message Types:

1. Connection Status (Server -> Client):

{
  type: "connection",
  status: "connected" | "disconnected",
  timestamp: string  // ISO timestamp
}

2. Heartbeat (Bidirectional):

{
  type: "ping" | "pong",
  timestamp: string  // ISO timestamp
}

3. Fill Request Status (Server -> Client):

{
  type: "fillRequest",
  success: boolean,
  request: {
    chainId: string,
    compact: {
      arbiter: string,
      sponsor: string,
      nonce: string,
      expires: string,
      id: string,
      amount: string,
      mandate: {
        chainId: number,
        tribunal: string,
        recipient: string,
        expires: string,
        token: string,
        minimumAmount: string,
        baselinePriorityFee: string,
        scalingFactor: string,
        salt: string
      }
    },
    sponsorSignature: string | null,
    allocatorSignature: string,
    context: {
      dispensation: string,
      dispensationUSD: string,
      spotOutputAmount: string,
      quoteOutputAmountDirect: string,
      quoteOutputAmountNet: string,
      deltaAmount?: string,
      slippageBips?: number,
      witnessTypeString: string,
      witnessHash: string,
      claimHash?: string
    }
  },
  error?: string,  // Present only if success is false
  transactionHash?: string,  // Present only if success is true
  details?: {  // Present only if success is true
    dispensationUSD: number,
    gasCostUSD: number,
    netProfitUSD: number,
    minProfitUSD: number
  }
}

4. Price Update (Server -> Client):

{
  type: "price_update",
  chainId: number,
  price: string,  // Price in USD
  timestamp: string  // ISO timestamp
}

5. Account Update (Server -> Client):

{
  type: "account_update",
  account: string,
  chainId: number,
  balances: Record<string, string>,  // Token balances in wei
  timestamp: string  // ISO timestamp
}

6. Error (Server -> Client):

{
  type: "error",
  code: string,
  message: string,
  timestamp: string  // ISO timestamp
}

Code Quality

• TypeScript for type safety
• Biome for linting and formatting
• Jest for testing
• Husky for Git hooks
• lint-staged for pre-commit checks

Deployment

The project includes a setup script for deploying to a cloud server with automatic HTTPS configuration using Let's Encrypt.

Prerequisites

• A domain name pointing to your server (A record)
• Ubuntu-based cloud server
• SSH access to the server

Deployment Steps

1. SSH into your server:

ssh user@your-server

2. Clone the repository:

git clone https://github.com/Uniswap/neutrofill.git
cd neutrofill

3. Run the setup script with your domain and IP:

./scripts/setup-server.sh your-domain.com your-server-ip

For example:

./scripts/setup-server.sh neutrofill.com 167.172.1.91

The script will:

• Install required dependencies (Node.js, nginx, certbot)
• Set up the project in /opt/neutrofill
• Configure nginx with WebSocket support
• Set up SSL certificates with Let's Encrypt
• Create and enable a systemd service
• Start the server

Monitoring

Monitor the server status:

sudo systemctl status neutrofill

View server logs:

sudo journalctl -u neutrofill -f

Testing Deployed Server

Test WebSocket connection:

wscat -c wss://your-domain.com/ws

Test broadcast endpoint:

curl -X POST https://your-domain.com/broadcast \
-H "Content-Type: application/json" \
-d '{ ... your payload ... }'

Test health endpoint:

curl https://your-domain.com/health

License

MIT