Web3 ProviderEngine

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

Status: WIP - expect breaking changes and strange behaviour

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. vap_call may trigger vap_getAccountBalance, vap_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,
  vap_hashrate: '0x00',
  vap_mining: false,
  vap_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.vapormask.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()

Built For Zero-Clients

The Vapory 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 Vapory '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

13.0.0

• txs included in blocks via vap-block-tracker@2.0.0

12.0.0

• moved block polling to vap-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

Current RPC method support:

static

• [x] web3_clientVersion
• [x] net_version
• [x] net_listening
• [x] net_peerCount
• [x] vap_protocolVersion
• [x] vap_hashrate
• [x] vap_mining
• [x] vap_syncing

filters

• [x] vap_newBlockFilter
• [x] vap_newPendingTransactionFilter
• [x] vap_newFilter
• [x] vap_uninstallFilter
• [x] vap_getFilterLogs
• [x] vap_getFilterChanges

accounts manager

• [x] vap_coinbase
• [x] vap_accounts
• [x] vap_sendTransaction
• [x] vap_sign
• [x] vap_signTypedData

vm

• [x] vap_call
• [x] vap_estimateGas

db source

• [ ] db_putString
• [ ] db_getString
• [ ] db_putHex
• [ ] db_getHex

compiler

• [ ] vap_getCompilers
• [ ] vap_compileLLL
• [ ] vap_compileSerpent
• [ ] vap_compileSolidity

shh gateway

• [ ] shh_version
• [ ] shh_post
• [ ] shh_newIdentity
• [ ] shh_hasIdentity
• [ ] shh_newGroup
• [ ] shh_addToGroup

data source ( fallback to rpc )

• vap_gasPrice
• vap_blockNumber
• vap_getBalance
• vap_getBlockByHash
• vap_getBlockByNumber
• vap_getBlockTransactionCountByHash
• vap_getBlockTransactionCountByNumber
• vap_getCode
• vap_getStorageAt
• vap_getTransactionByBlockHashAndIndex
• vap_getTransactionByBlockNumberAndIndex
• vap_getTransactionByHash
• vap_getTransactionCount
• vap_getTransactionReceipt
• vap_getUncleByBlockHashAndIndex
• vap_getUncleByBlockNumberAndIndex
• vap_getUncleCountByBlockHash
• vap_getUncleCountByBlockNumber
• vap_sendRawTransaction
• vap_getLogs ( not used in web3.js )

( not supported )

• vap_getWork
• vap_submitWork
• vap_submitHashrate ( not used in web3.js )