# squarelink-provider-engine

> Squarelink's Web3 Provider Engine

Latest version **15.0.5** (published 2019-08-27) · MIT license · 0 weekly downloads

## Install

```sh
npm install squarelink-provider-engine
pnpm add squarelink-provider-engine
yarn add squarelink-provider-engine
bun add squarelink-provider-engine
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 15.0.5 |
| Published | 2019-08-27 |
| First published | 2019-05-15 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 22 |
| Unpacked size | 2 MB |
| Known vulnerabilities | 0 (+1 in 1 direct dependencies) |
| Install scripts | no |
| Author | Alex Patin |
| Maintainers | thealexpatin |

## Links

- npm: https://www.npmjs.com/package/squarelink-provider-engine
- Repository: https://github.com/Squarelink-inc/Web3ProviderEngine
- Homepage: https://github.com/Squarelink-inc/Web3ProviderEngine#readme
- Issues: https://github.com/Squarelink-inc/Web3ProviderEngine/issues
- npm.io page: https://npm.io/package/squarelink-provider-engine

## Dependencies (22)

- [ws](https://npm.io/package/ws.md) ^5.1.1
- [xhr](https://npm.io/package/xhr.md) ^2.2.0
- [async](https://npm.io/package/async.md) ^2.5.0
- [clone](https://npm.io/package/clone.md) ^2.0.0
- [xtend](https://npm.io/package/xtend.md) ^4.0.1
- [backoff](https://npm.io/package/backoff.md) ^2.5.0
- [request](https://npm.io/package/request.md) ^2.85.0
- [semaphore](https://npm.io/package/semaphore.md) ^1.0.3
- [cross-fetch](https://npm.io/package/cross-fetch.md) ^2.1.0
- [eth-sig-util](https://npm.io/package/eth-sig-util.md) ^1.4.2
- [ethereumjs-tx](https://npm.io/package/ethereumjs-tx.md) ^1.2.0
- [ethereumjs-vm](https://npm.io/package/ethereumjs-vm.md) ^2.3.4
- [json-rpc-error](https://npm.io/package/json-rpc-error.md) ^2.0.0
- [ethereumjs-util](https://npm.io/package/ethereumjs-util.md) ^5.1.5
- [readable-stream](https://npm.io/package/readable-stream.md) ^2.2.9
- [ethereumjs-block](https://npm.io/package/ethereumjs-block.md) ^1.2.2
- [eth-block-tracker](https://npm.io/package/eth-block-tracker.md) ^4.4.1
- [eth-json-rpc-infura](https://npm.io/package/eth-json-rpc-infura.md) ^3.1.0
- [promise-to-callback](https://npm.io/package/promise-to-callback.md) ^1.0.0
- [eth-json-rpc-filters](https://npm.io/package/eth-json-rpc-filters.md) ^4.0.2
- [json-stable-stringify](https://npm.io/package/json-stable-stringify.md) ^1.0.1
- [eth-json-rpc-middleware](https://npm.io/package/eth-json-rpc-middleware.md) ^4.1.1

## Recent versions

- 15.0.5 (latest) — 2019-08-27
- 15.0.4 — 2019-08-16
- 15.0.3 — 2019-06-24
- 15.0.2 — 2019-05-28
- 15.0.1 — 2019-05-27
- 15.0.0 — 2019-05-15

## README

# Web3 ProviderEngine

[![Greenkeeper badge](https://badges.greenkeeper.io/MetaMask/provider-engine.svg)](https://greenkeeper.io/)

Web3 ProviderEngine is a tool for composing your own [web3 providers](https://github.com/ethereum/wiki/wiki/JavaScript-API#web3).


### 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.

```js
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:
```js
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](https://github.com/ethereum/wiki/wiki/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`](https://github.com/MetaMask/eth-json-rpc-middleware)
- 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`](https://github.com/kumavis/eth-block-tracker)@2.0.0

##### 12.0.0

- moved block polling to [`eth-block-tracker`](https://github.com/kumavis/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

---
_Source: https://npm.io/package/squarelink-provider-engine · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._