Web3 ProviderEngine

Web3 ProviderEngine is a tool for composing your own web3 providers.

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.

const ProviderEngine = require('web3-provider-engine')
const CacheSubprovider = require('web3-provider-engine/subproviders/cache.js')
const FixtureSubprovider = require('web3-provider-engine/subproviders/fixture.js')
const FilterSubprovider = require('web3-provider-engine/subproviders/filters.js')
const VmSubprovider = require('web3-provider-engine/subproviders/vm.js')
const HookedWalletSubprovider = require('web3-provider-engine/subproviders/hooked-wallet.js')
const NonceSubprovider = require('web3-provider-engine/subproviders/nonce-tracker.js')
const RpcSubprovider = require('web3-provider-engine/subproviders/rpc.js')

var engine = new ProviderEngine()
var 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 CacheSubprovider())

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

// pending nonce
engine.addProvider(new NonceSubprovider())

// vm
engine.addProvider(new VmSubprovider())

// id mgmt
engine.addProvider(new HookedWalletSubprovider({
  getAccounts: function(cb){ ... },
  approveTransaction: function(cb){ ... },
  signTransaction: function(cb){ ... },
}))

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

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

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

// start polling for blocks
engine.start()

When importing in webpack:

import * as Web3ProviderEngine  from 'web3-provider-engine';
import * as RpcSource  from 'web3-provider-engine/subproviders/rpc';
import * as HookedWalletSubprovider from 'web3-provider-engine/subproviders/hooked-wallet';

Built For Zero-Clients

The Ethereum JSON RPC was not designed to have one node service many clients. However a smaller, lighter subset of the JSON RPC can be used to provide the blockchain data that an Ethereum 'zero-client' node would need to function. We handle as many types of requests locally as possible, and just let data lookups fallback to some data source ( hosted rpc, blockchain api, etc ). Categorically, we don’t want / can’t have the following types of RPC calls go to the network:

id mgmt + tx signing (requires private data)
filters (requires a stateful data api)
vm (expensive, hard to scale)

Change Log

15.0.0

uses eth-block-tracker@4, but still provides block body on ('block', 'latest', and 'rawBlock'). Other events ('sync') provide block number hex string instead of block body.
SubscriptionsSubprovider automatically forwards events to provider
replacing subprovider implementations with those in eth-json-rpc-engine
browserify: moved to babelify@10 + @babel/core@7

14.0.0

default dataProvider for zero is Infura mainnet REST api
websocket support
subscriptions support
remove solc subprovider
removed dist from git (but published in npm module)
es5 builds in dist/es5
zero + ProviderEngine bundles are es5
web3 subprovider renamed to provider subprovider
error if provider subprovider is missing a proper provider
removed need to supply getAccounts hook
fixed hooked-wallet-ethtx message signing
fixed hooked-wallet default txParams

13.0.0

txs included in blocks via eth-block-tracker@2.0.0

12.0.0

moved block polling to eth-block-tracker.

11.0.0

zero.js - replaced http subprovider with fetch provider (includes polyfill for node).

10.0.0

renamed HookedWalletSubprovider personalRecoverSigner to recoverPersonalSignature

9.0.0

pollingShouldUnref option now defaults to false

NF-Repo/web3-provider-engine