`web3-provider-nginx`

Installation

npm install @backbonecabal/web3-provider-nginx

Differences from original package

Written in Typescript
Standard ES6 modules, designed for the browser first
Designed to be extended with a properly exported Subprovider interface
Base class implements new EthereumProvider standard
Compatible with latest versions of web3.js
Heavier dependencies removed to keep base package light (primarily all dependencies that rely on elliptic)
Many small bug fixes and improvements
Reimplement VmSubprovider as a separate package
Reimplement NonceTracker as a separate package
Improve test coverage

Composable

Built to be modular - works via a stack of 'sub-providers' which are like normal web3 providers but only handle a subset of rpc methods.

The subproviders can emit new rpc requests in order to handle their own; e.g. eth_call may trigger eth_getAccountBalance, eth_getCode, and others. The provider engine also handles caching of rpc request results.

import {
  default as ProviderEngine,
  BlockCacheSubprovider,
  FixtureSubprovider,
  FilterSubprovider,
  FetchSubprovider
} from '@backbonecabal/provider-engine';

const engine = new ProviderEngine();
const web3 = new Web3(engine);

// static results
engine.addProvider(new FixtureSubprovider({
  web3_clientVersion: 'ProviderEngine/v0.0.0/javascript',
  net_listening: true,
  eth_hashrate: '0x00',
  eth_mining: false,
  eth_syncing: true,
}));

// cache layer
engine.addProvider(new BlockCacheSubprovider());

// filters
engine.addProvider(new FilterSubprovider());

// data source
engine.addProvider(new FetchSubprovider({
  rpcUrl: 'https://testrpc.metamask.io/',
}));

// log new blocks
engine.on('block', (block) => {
  console.log('================================')
  console.log('BLOCK CHANGED:', '#'+block.number.toString('hex'), '0x'+block.hash.toString('hex'))
  console.log('================================')
});

// network connectivity error
engine.on('error', (err) => {
  // report connectivity errors
  console.error(err.stack);
});

// start polling for blocks
engine.start();

Writing your own Subprovider

It's easy to extend the functionality of this module by writing your own Subprovider instance.

See src/subprovider.ts for the full interface.

import { Subprovider } from '@backbonecabal/provider-engine';

export default class MySubprovider extends Subprovider {

  // Only requirement is to implement handleRequest
  public handleRequest(payload, next, end) {
    // The payload includes the original JSON RPC request
    if (payload.method === 'eth_helloWorld') {
      // Call end() to handle the request in this subprovider
      end('hello world!');
    } else {
      // Call next() to fall-through to the next request in the stack
      next();
    }
  }

}

License

MIT

sambacha / web3-provider-engine