Infura web3 provider for Events (.get & .watch)

Question

I am using infura for connecting to testnet/mainnet as my server side web3 provider.

This works for most requests and operations, but it does not seem to work for Events.

const allEvents = (event, callback) =>
  event({}, { fromBlock: 0, toBlock: 'latest' }).get((error, results) => {
  if (error) return callback(error);
  results.forEach(result => callback(null, result));
  event().watch(callback);
});

allEvents(contractInstance.Event, eventCallback);

The code above runs locally (connecting to a localhost:8545 provider / geth) but does not run if I use infura:

// THIS DOES NOT WORK:
const web3Url = `https://ropsten.infura.io/${infuraKey}`;
const web3 = new Web3(new Web3.providers.HttpProvider(web3Url));

// THIS WORKS:
const web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'));

Any suggestions or alternatives for web3 providers? Thanks.

Answer 1

Infura currently doesn't support WebSockets (required for events using Web3 v1, otherwise you get the error "The current provider doesn't support subscriptions" when using infura as HttpProvider), so what you have to do is run a local geth node that connects and syncs to the network.

Here we enable the websocket flag and allow any origin to connect to the local geth node that is syncing with the rinkeby testnet:

geth --rinkeby --ws --wsport=8546 --wsorigins="*" --datadir=$HOME/.rinkeby --cache=512 --rpc --rpcapi="personal,eth,network" --rpcport=8545 --fast --bootnodes=enode://a24ac7c5484ef4ed0c5eb2d36620ba4e4aa13b8c84684e1b4aab0cebea2ae45cb4d375b77eab56516d34bfbd3c1a833fc51296ff084b770b94fb9028c4d25ccf@52.169.42.101:30303

To check the syncing status:

geth attach ipc:$HOME/.rinkeby/geth.ipc
> eth.syncing

Once it's done syncing you can connect using the WebsocketProvider:

const web3 = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'))

You should now be able to receive events:

myContract.events.allEvents((error, event) => {
  if (error) {
    console.error(error)
    return false
  }

  console.log(event)
})

Tested this with geth v1.6.5 and web3 v1.0.0.

Update Oct 11, 2017:

Infura is experimenting with websocket support. You can ask for beta access in this github issue thread:

https://github.com/INFURA/infura/issues/29

Answer 2

I have been using Infura with web3 1.0 in mainnet. Here is my code, hope it helps

var Web3 = require('web3')
var request = require('request');
var contract = require('truffle-contract')
var zastrin_pay_artifacts = require('./build/contracts/ZastrinPay.json')
var ws_provider = 'wss://mainnet.infura.io/ws'
var web3 = new Web3(new Web3.providers.WebsocketProvider(ws_provider))
var ZastrinPay = contract(zastrin_pay_artifacts);
var econtract = new web3.eth.Contract(ZastrinPay.abi, '<address>');

console.log("Starting listner ....");

newPaymentEvent = econtract.events.NewPayment({fromBlock: 5424000, address: '<address>', toBlock: 'latest'}, function(error, result){
  if (result !== undefined) {
    var args = result.returnValues;
    args["_txn"] = result.transactionHash;
    console.log(args);
  }
});

Answer 3

QuikNode.io works well. Dedicated ETH node supporting both https:// and wss:// (websockets). Supports event subscriptions and txpool/queue API calls; Parity and Geth clients; MainNet/Ropsten/Rinkeby/Kovan too. Can sign up on website and have node running in minutes.