Event not being captured in web3js

Question

I have the following (very simple) oracle contract. All I want it to do is manage data on the chain that is returned by an open source API - I'll use this data in another contract. I am able to call the methods of my contract without any issue using web3js, but I am unable to listen for events on a socket. I should be seeing console.log('Event firing ', event) output something, but I do not. If helpful, I am running ganache and truffle locally to host the contract

When I hit the http://localhost:3000/api/oracle endpoint, I get the following (source code below the output). Can someone help me understand why I'm not capturing the events correctly?

[0] 9:36:44 AM - Found 0 errors. Watching for file changes.
[1] Running on 3000 ⚡
[1] Endpoint called
[1] Contract response Done

//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.0;

contract SnapshotOracle {
  // Contract owner
  address public owner;

  string[] public voters;

  // Callback function
  event CallbackGetVotes(address owner);

  constructor() {
    owner = msg.sender;
  }

  // This is called first, which emits an event
  // that fetches new data
  function updateVotes() public returns (string memory) {
    emit CallbackGetVotes(owner);
    return "Done";
  }

  // Once the data is fatched by the service,
  // setVotes is called to set that data
  function setVotes(string[] memory _voters) public {
    require(msg.sender == owner);
    voters = _voters;
  }

  // Finally, getVotes is called to get the new data
  function getVotes() public view returns (string[] memory) {
    return voters;
  }
}

// Simple Node oracle service to interact with oracle contract
import express, { Express, Request, Response } from 'express';
import bodyParser from 'body-parser';
import helmet from 'helmet';
import dotenv from 'dotenv';

import Web3 from 'web3'
import OracleContract from './contracts/SnapshotOracle.json'
import { AbiItem } from 'web3-utils'

dotenv.config();

const PORT = process.env.PORT || 3000;
const app: Express = express();

app.use(helmet());
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

// Web socket to contract
const CHAIN_PORT = '7545' 
const ORACLE_ADDR = '0x05dbB4b1C895C593b66686b5234D3cD80D18E460'
const web3 = new Web3(`ws://127.0.0.1:${CHAIN_PORT}`)
const oracleContract = new web3.eth.Contract(OracleContract.abi as AbiItem[], ORACLE_ADDR)

web3.eth.getAccounts((err, accounts) => {
  const a = oracleContract.events.CallbackGetVotes({owner: accounts[0]})
  .on('data', (event: any) => {
    console.log('Event firing ', event)
    // TODO: Run API Request
    // TODO: Save result of API request to contract state
  })
})

app.get('/api/oracle', (req: Request, res: Response) => {
  const web3 = new Web3(`http://127.0.0.1:${CHAIN_PORT}`)
  const oracleContract = new web3.eth.Contract(OracleContract.abi as AbiItem[], ORACLE_ADDR)
  console.log('Endpoint called')

  web3.eth.getAccounts(async (err, accounts) => {
    const t = await oracleContract.methods.updateVotes().call({owner: accounts[0]})
    console.log('Contract response', t)

    setTimeout(async () => {
      const votes = await oracleContract.methods.getVotes().call()
      res.send(votes)
    }, 3000)
  })
});

app.listen(PORT, () => console.log(`Running on ${PORT} ⚡`));

Answer 1

The problem is that you aren't creating a transaction oracleContract.methods.updateVotes().call() is calling updateVotes as view function. You have to use .send instead.

const t = await oracleContract.methods.updateVotes().send({owner: accounts[0]})
console.log("Transaction receipt: ", t)