blockchain - 如何订阅“日志事件”并在 ThunderCore 上获取通知？

Question

当我想订阅log事件并在 ThunderCore 上获取通知时，我遇到了一些问题。

据我所知，我似乎应该使用 websocket 和eth_subscribe. 有没有例子？？

或者，是否有其他解决方案可以实现我的目标？

Answer 1

listen_to_thundercore_mainnet.js

/**
 * Connect to Thundercore mainnet and listen for tips to a specific smart contract address.
 */

const Web3 = require('web3');
var provider = 'wss://mainnet-ws.thundercore.com';
var web3 = new Web3(provider);


let listenOnce = () => {
  // Create a connection to Thundercore mainet.

  const smartContractAddress = '0xb7d82e5B73e01bB4c1cFB1448f1215bf165929a2'

  var subscription = web3.eth.subscribe('logs', {
    address: smartContractAddress,
  }, (error, result) => {
    if (error) {
      console.log(error)
      console.log('Reconnecting to Thundercore mainnet.')    
      setTimeout( () => {
        // Re-instantiating web3 is needed in case the connection is dropped.
        web3 = new Web3(provider);
        _listen()
      }, 5000);
    }
  })
  .on('connected', (subscriptionId) => {
    console.log('connected')
  })
  .on('data', (log) => {
    console.log(log);
  })
  .on("changed", (log) => {
    console.log('changed')
  })
  
  return subscription
}

const _listen = async () => {
  let tips = listenOnce();
  console.log('Connected to Thundercore mainnet.')

  // web3 subscription times out at 60 secs. Close and reopen at 50 secs.
  setInterval( () => {
    tips.unsubscribe( (error, success) => {
      if(error) {
        console.log('Failed to disconnect from Thundercore mainnet!');
      }
      if(success) {
        console.log('disconnected');
      }
    });
    tips = listenOnce();
  }, (50 * 1000));
}


_listen()

使用 NodeJS 运行

node listen_to_thundercore_mainnet.js

Thundercore 会在 60 秒后断开您的连接。所以我们在此之前故意断开连接并立即重新连接。这种方法在跟踪流量巨大的合约时会错过一些交易。

Answer 2

通过以下方式获取有关 ThunderCore 上新合约事件的通知：

1. 使用 Websocket 连接到 RPC 节点，例如https://testnet-rpc.thundercore.com
2. 在事件上调用eth_subscribeRPC 方法logs

自包含示例

SimpleRecord.sol

pragma solidity ^0.4.25;

contract SimpleRecord {
    event Record(
        address indexed _from,
        uint _value
    );

    function write() payable public {
        emit Record(msg.sender, msg.value);
    }
}

要生成Record事件，请运行simple-record-write以查看通知运行simple-record-log-subscribe：

const process = require('process')
const path = require('path')
const fs = require('fs')
const Web3 = require('web3')
const Accounts = require('web3-eth-accounts')
const util = require('util')

// truffle migrate --reset --network thunder-mainnet
const thunderWsUrl = 'wss://mainnet-ws.thundercore.com'
// truffle migrate --reset --network thunder-testnet
//const thunderWsUrl = 'wss://testnet-ws.thundercore.com'

const programName = () => {
    return path.basename(process.argv[1])
}

const web3Url = () => {
    let u = process.env['WEB3_PROVIDER_URI']
    if (u === undefined) {
        u = thunderWsUrl
    }
    return u
}

const signTx = async (fromAccount, tx) => {
    const signedTx = await fromAccount.signTransaction(tx)
    return signedTx.rawTransaction // hex string
}

const setup = async () => {
    const privateKeys = fs.readFileSync(path.join(__dirname, '..', '.private-keys'), {encoding: 'ascii'}).split('\n').filter(x => x.length > 0)
    const accounts = new Accounts()
    const account = accounts.privateKeyToAccount('0x' + privateKeys[0])
    const jsonBuf = fs.readFileSync(path.join(__dirname, '..', 'build', 'contracts', 'SimpleRecord.json'))
    const contractData = JSON.parse(jsonBuf)
    const contractAbi = contractData['abi']
    const web3ProviderUrl = web3Url()
    const web3 = new Web3(web3ProviderUrl)
    const networkId = await web3.eth.net.getId()

    let deployedNetwork, contractAddress
    try {
        deployedNetwork = contractData['networks'][networkId]
        contractAddress = deployedNetwork['address']
    } catch (err) {
        msg = `error getting deployedNetwork: ${err}`
        throw new Error(msg)
    }
    const contract = new web3.eth.Contract(contractAbi, contractAddress)
    return [ web3ProviderUrl, web3, networkId, contractAddress, contract, account ]
}

const prettyPrint = (o) => {
   return util.inspect(o, {showHidden: false, depth: null, colors: true})
}

const recordWrite = async () => {
    const [web3ProviderUrl, web3, chainId, contractAddress, contract, fromAccount] = await setup()
    console.log('web3ProviderUrl:', web3ProviderUrl)
    const txnData = contract.methods.write().encodeABI()
    console.log('account.address:', fromAccount.address)
    const promiseResults = await Promise.all([
        web3.eth.getTransactionCount(fromAccount.address),
        web3.eth.getGasPrice(),
    ])
    const nonce = promiseResults[0]
    const gasPrice = promiseResults[1]
    const tx = {
        'gasLimit': 0,
        'chainId': chainId,
        'gasPrice': gasPrice,
        'nonce': Web3.utils.toHex(nonce),
        'from': fromAccount.address,
        'to': contractAddress,
        'value': 0xbeef,
        'data': txnData,
    }
    const gasMultiple = 2.0
    tx.gasLimit = (await web3.eth.estimateGas(tx)) * gasMultiple
    console.log('tx:', prettyPrint(tx))
    const rawTxStr = await signTx(fromAccount, tx)
    const r = await web3.eth.sendSignedTransaction(rawTxStr)
    console.log('sendTransaction: receipt:', prettyPrint(r))
    return 0
}

const logSubscribe = () => {
    return new Promise((resolve, reject) => {
        setup().then(([web3ProviderUrl, web3, chainId, contractAddress, contract, account]) => {
            let eventCount = 0
            console.log('web3ProviderUrl:', web3ProviderUrl)
            console.log('contractAddress:', contractAddress)
            console.log('contract.options.jsonInterface:', prettyPrint(contract.options.jsonInterface))
            const eventAbis = contract.options.jsonInterface.filter((abiObj) => abiObj.type === 'event')
            web3.eth.subscribe('logs', { address: contractAddress }, (err, log) => {
                console.log('eth.subscribe("logs") callback')
                if (err) {
                    console.log('logs callback, err:', err)
                    reject(err)
                    return
                }
                eventCount++
                console.log(`log[${eventCount}]:`, log)
                const eventSig = log.topics[0]
                for (let abi of eventAbis) {
                    if (eventSig === abi.signature) {
                        const decoded = web3.eth.abi.decodeLog(abi.inputs, log.data, log.topics.slice(1))
                        console.log('Decoded Event:', prettyPrint(abi), '\n', prettyPrint(decoded))
                        resolve(0)
                        return
                    }
                }
            })
        })
    })
}

(async () => {
    if (programName().endsWith('-write')) {
        process.exit(await recordWrite())
    } else if (programName().endsWith('-log-subscribe')) {
        process.exit(await logSubscribe())
    } else {
        console.error(`unsupported program name: "${programName()}"`)
        process.exit(2)
    }
})()

在repo的subscribe-to-logs分支中查看完整的项目。field-support