Ethereum JSON-RPC Proxy

This Node.js script acts as a proxy for Ethereum JSON-RPC requests. It checks the health of multiple Ethereum RPC endpoints and forwards requests to the first available and healthy node.

Features

• Health Checks: Periodically checks the status of configured RPC URLs, verifying uptime, sync status, and recent block timestamp.
• Automatic Failover: Forwards requests to the first available and healthy RPC node.
• Minimal Dependencies: Uses only built-in Node.js modules (http, https, url).
• Environment Configuration: Reads RPC URLs from the RPC_URLS environment variable.
• Error Handling: Includes robust error handling for RPC calls, request forwarding, and JSON parsing.
• Logging: Provides informative console logs about RPC status and errors.

Installation

1. Make sure you have Node.js installed.
2. Save the script (e.g., as rpc-proxy.js).

Usage

1. Set the RPC_URLS environment variable, listing your Ethereum RPC URLs separated by commas:

   export RPC_URLS="[https://mainnet.infura.io/v3/](https://mainnet.infura.io/v3/)<YOUR_INFURA_PROJECT_ID>,[https://another.rpc.url](https://another.rpc.url)"

   Replace <YOUR_INFURA_PROJECT_ID> and https://another.rpc.url with your actual RPC endpoint URLs. You can use Infura, Alchemy, or other providers.

2. Run the script:

   node rpc-proxy.js

3. The proxy will start listening on port 3000 by default. You can change this using the PORT environment variable:

   export PORT=8080
   node rpc-proxy.js

4. Send your JSON-RPC requests to the proxy server:

   curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc": "2.0", "method": "eth_blockNumber", "params": [], "id": 1}' http://localhost:3000

Configuration

• RPC_URLS: A comma-separated list of Ethereum RPC URLs. This is a required environment variable.
• PORT: The port the proxy server listens on (optional, defaults to 3000).

Health Check Details

The proxy performs the following checks for each RPC URL:

• Uptime: Attempts to connect to the RPC endpoint.
• Sync Status: Calls the eth_syncing method. A response of false indicates the node is not syncing.
• Block Timestamp: Calls the eth_getBlockByNumber method with latest and checks if the block's timestamp is within the last 5 minutes. This helps ensure the node's clock is accurate.

Error Handling

The proxy handles the following errors:

• Invalid RPC_URLS environment variable.
• Errors during RPC health checks.
• Errors forwarding requests to the RPC node.
• JSON parsing errors.

Logging

The proxy logs the following information to the console:

• Proxy server startup message.
• RPC health check results.
• Errors encountered.

Contributing

Contributions are welcome! Please open an issue or submit a pull request.

License

MIT