kafka-dance-api/app.js

const { Kafka } = require('kafkajs');

const { readConfig, storeConfig } = require('./config')
const express = require('express');
const cors = require('cors')
const ws = require('ws')
const path = require('path');
const cookieParser = require('cookie-parser');
const logger = require('morgan');
const query = require('./query')
const { buildEscape } = require('./safely-exit')

const config = readConfig()
console.log('CONFIG', config)

/**
 * Log out an object and return it.
 *
 * @param object The object to log
 * @param f Optional param to specify an alternative log function. E.g. console.error
 * @returns {*}
 */
const c = (object, f = console.log) => {
  f(object)
  return object;
}

const buildCluster = (clusterConfig, connect = true) => {
  const kafkaConfig = {...clusterConfig}
  delete kafkaConfig.clusterName // new Kafka() tries to use this same value

  const kafka = new Kafka(kafkaConfig)
  const admin = kafka.admin()
  const cluster = {
    kafka,
    admin,
    config: clusterConfig
  }
  admin.connect().catch(e => console.error(cluster.error = e.toString()))
  return cluster
}

const clusters =
  Object.fromEntries(Object.entries(config.clusters)
    .map(([clusterName, clusterData]) => [clusterName, buildCluster(clusterData)]))
console.log('CLUSTERS', clusters)

const app = express();

app.use(cors({
  origin: 'http://localhost:5173'
}))
app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

const router = express.Router()

process.on('unhandledRejection', console.error)

/* GET topics listing. */
router.get('/topics/:cluster', async (req, res, _next) => {
  const legalName = topicName => !topicName.startsWith("__")
  try {
    const topicList = (await clusters[req.params.cluster]?.admin.listTopics() || [])
    res.send(topicList.filter(legalName))
  } catch (e) {
    res.status(502).send({
      error: `Could not connect to cluster '${req.params.cluster}'`,
      errorDetails: e.toString()
    })
  }
})

const passwordPlaceholder = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXX'

const getClusterData = () =>
  Object.fromEntries(
    Object.entries(clusters).map(([key, value]) => {
      value = JSON.parse(JSON.stringify(value))
      if (value.config.sasl?.password) {
        value.config.sasl.password = passwordPlaceholder
      }
      return [key, value.config]
    }))

router.get('/clusters', async (req, res, _next) => {
  console.log('/clusters')
  res.send(getClusterData())
})

router.post('/clusters', async (req, res, _next) => {
  console.log('/clusters post body', req.body)
  const clusterName = req.body.clusterName
  config.clusters[clusterName] = req.body
  clusters[clusterName] = buildCluster(req.body)
  res.send(getClusterData())
  await storeConfig(config)
})

router.post('/clusters/delete', async (req, res, _next) => {
  const clusterName = req.body.clusterName
  // Kill all consumers connected to this cluster and notify those clients via their websocket
  consumers.forEach(([{ consumer, cluster }, socket]) => {
    if (clusters[clusterName] !== cluster) {
      // TODO This reference equality may not be sufficient?
      return
    }
    killConsumer(consumer)
    const sendDeletedMessage = buildSocketMessageSender({ type: 'cluster_deleted', socket })
    sendDeletedMessage(clusterName)
  })
  delete clusters[clusterName]
  delete config.clusters[clusterName]
  await storeConfig(config)
  res.send(getClusterData())
})

router.put('/clusters', async (req, res, _next) => {
  const hasPlaceholderPassword = req.body.sasl.password === passwordPlaceholder
  const clusterName = req.body.clusterName
  if (hasPlaceholderPassword) {
    req.body.password = config.clusters[clusterName].password
  }
  config.clusters[clusterName] = req.body
  clusters[clusterName] = buildCluster(req.body)
  res.send('')
  await storeConfig(config)
})

app.use(router)

const buildSocketMessageSender = ({ type, socket }) => message => {
  socket.send(JSON.stringify({
    type,
    message
  }))
}

const realTimeSearch = async ({ kafka, socket, topic }) =>
  query.realTimeMessageSearch({
    kafka,
    topic,
    onMessage: buildSocketMessageSender({ socket, type: 'message' })
  });

const oneShotSearch = async ({ kafka, socket, topic, maxItems }) =>
  query.searchMessages({
    kafka,
    topic,
    maxItems,
    onDone: buildSocketMessageSender({ socket, type: 'count' }),
    onBatchDone: buildSocketMessageSender({ socket, type: 'item_count' })
  })

/**
 * @type {WebSocketServer}
 */
const wsServer = new ws.WebSocketServer({
  noServer: true
})

/** @type {Map<WebSocket, ({consumer: Consumer, cluster: { kafka, admin, config }})>} */
const consumers = new Map()

buildEscape(consumers, clusters)

wsServer.on('connection', socket => {
  socket.send('CONNECTED')
  socket.on('close', async () => {
    await killConsumer(consumers.get(socket).consumer)
    consumers.delete(socket)
  })

  socket.on('message', async message => {
    message = JSON.parse(message)

    if (message.mode === 'kill') {
      console.log('KILLING SOCKET')
      await killConsumer(consumers.get(socket).consumer)
      consumers.delete(socket)
      return
    }
    const startSearch = message.mode === 'realTime' ? realTimeSearch : oneShotSearch
    const cluster = clusters[message.cluster]

    const run = async () => {
      const consumerCluster = {
        consumer: await startSearch({
          kafka: cluster.kafka,
          topic: message.topic,
          maxItems: message.maxItems,
          socket
        }),
        cluster
      }
      consumers.set(socket, consumerCluster);
    }

    run().catch(async e => {
      console.error('run() error occurred!', e.toString())
      await killConsumer(consumers.get(socket).consumer)
      // Try again ONCE on failure
      run().catch(ee => socket.send('ERROR: ' + ee))
    })
  })
})

const killConsumer = async consumer => {
  await consumer?.stop()
  await consumer?.disconnect()
}

module.exports = {
  app,
  wsServer
}