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. 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)
engine.addProvider(new FixtureSubprovider({
web3_clientVersion: 'ProviderEngine/v0.0.0/javascript',
net_listening: true,
eth_hashrate: '0x00',
eth_mining: false,
eth_syncing: true,
})
engine.addProvider(new CacheSubprovider())
engine.addProvider(new FilterSubprovider())
engine.addProvider(new NonceSubprovider())
engine.addProvider(new VmSubprovider())
engine.addProvider(new HookedWalletSubprovider({
getAccounts: function(cb){ ... },
approveTransaction: function(cb){ ... },
signTransaction: function(cb){ ... },
}))
engine.addProvider(new RpcSubprovider({
rpcUrl: 'https://testrpc.metamask.io/',
}))
engine.on('block', function(block){
console.log('================================')
console.log('BLOCK CHANGED:', '#'+block.number.toString('hex'), '0x'+block.hash.toString('hex'))
console.log('================================')
})
engine.on('error', function(err){
console.error(err.stack)
})
engine.start()
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)
Current RPC method support:
static
filters
accounts manager
vm
db source
compiler
shh gateway
data source ( fallback to rpc )
- eth_gasPrice
- eth_blockNumber
- eth_getBalance
- eth_getBlockByHash
- eth_getBlockByNumber
- eth_getBlockTransactionCountByHash
- eth_getBlockTransactionCountByNumber
- eth_getCode
- eth_getStorageAt
- eth_getTransactionByBlockHashAndIndex
- eth_getTransactionByBlockNumberAndIndex
- eth_getTransactionByHash
- eth_getTransactionCount
- eth_getTransactionReceipt
- eth_getUncleByBlockHashAndIndex
- eth_getUncleByBlockNumberAndIndex
- eth_getUncleCountByBlockHash
- eth_getUncleCountByBlockNumber
- eth_sendRawTransaction
- eth_getLogs ( not used in web3.js )
( not supported )
- eth_getWork
- eth_submitWork
- eth_submitHashrate ( not used in web3.js )