hometown/streaming/index.js

import os from 'os';
import cluster from 'cluster';
import dotenv from 'dotenv'
import express from 'express'
import http from 'http'
import redis from 'redis'
import pg from 'pg'
import log from 'npmlog'
import url from 'url'
import WebSocket from 'ws'
import uuid from 'uuid'

const env = process.env.NODE_ENV || 'development'

dotenv.config({
  path: env === 'production' ? '.env.production' : '.env'
})

if (cluster.isMaster) {
  // cluster master

  const core = +process.env.STREAMING_CLUSTER_NUM || (env === 'development' ? 1 : Math.max(os.cpus().length - 1, 1))
  const fork = () => {
    const worker = cluster.fork();
    worker.on('exit', (code, signal) => {
      log.error(`Worker died with exit code ${code}, signal ${signal} received.`);
      setTimeout(() => fork(), 0);
    });
  };
  for (let i = 0; i < core; i++) fork();
  log.info(`Starting streaming API server master with ${core} workers`)

} else {
  // cluster worker

  const pgConfigs = {
    development: {
      database: 'mastodon_development',
      host:     '/var/run/postgresql',
      max:      10
    },

    production: {
      user:     process.env.DB_USER || 'mastodon',
      password: process.env.DB_PASS || '',
      database: process.env.DB_NAME || 'mastodon_production',
      host:     process.env.DB_HOST || 'localhost',
      port:     process.env.DB_PORT || 5432,
      max:      10
    }
  }

  const app    = express()
  const pgPool = new pg.Pool(pgConfigs[env])
  const server = http.createServer(app)
  const wss    = new WebSocket.Server({ server })

  const redisClient = redis.createClient({
    host:     process.env.REDIS_HOST     || '127.0.0.1',
    port:     process.env.REDIS_PORT     || 6379,
    password: process.env.REDIS_PASSWORD
  })

  const subs = {}

  redisClient.on('pmessage', (_, channel, message) => {
    const callbacks = subs[channel]

    log.silly(`New message on channel ${channel}`)

    if (!callbacks) {
      return
    }

    callbacks.forEach(callback => callback(message))
  })

  redisClient.psubscribe('timeline:*')

  const subscribe = (channel, callback) => {
    log.silly(`Adding listener for ${channel}`)
    subs[channel] = subs[channel] || []
    subs[channel].push(callback)
  }

  const unsubscribe = (channel, callback) => {
    log.silly(`Removing listener for ${channel}`)
    subs[channel] = subs[channel].filter(item => item !== callback)
  }

  const allowCrossDomain = (req, res, next) => {
    res.header('Access-Control-Allow-Origin', '*')
    res.header('Access-Control-Allow-Headers', 'Authorization, Accept, Cache-Control')
    res.header('Access-Control-Allow-Methods', 'GET, OPTIONS')

    next()
  }

  const setRequestId = (req, res, next) => {
    req.requestId = uuid.v4()
    res.header('X-Request-Id', req.requestId)

    next()
  }

  const accountFromToken = (token, req, next) => {
    pgPool.connect((err, client, done) => {
      if (err) {
        next(err)
        return
      }

      client.query('SELECT oauth_access_tokens.resource_owner_id, users.account_id FROM oauth_access_tokens INNER JOIN users ON oauth_access_tokens.resource_owner_id = users.id WHERE oauth_access_tokens.token = $1 LIMIT 1', [token], (err, result) => {
        done()

        if (err) {
          next(err)
          return
        }

        if (result.rows.length === 0) {
          err = new Error('Invalid access token')
          err.statusCode = 401

          next(err)
          return
        }

        req.accountId = result.rows[0].account_id

        next()
      })
    })
  }

  const authenticationMiddleware = (req, res, next) => {
    if (req.method === 'OPTIONS') {
      next()
      return
    }

    const authorization = req.get('Authorization')

    if (!authorization) {
      const err = new Error('Missing access token')
      err.statusCode = 401

      next(err)
      return
    }

    const token = authorization.replace(/^Bearer /, '')

    accountFromToken(token, req, next)
  }

  const errorMiddleware = (err, req, res, next) => {
    log.error(req.requestId, err)
    res.writeHead(err.statusCode || 500, { 'Content-Type': 'application/json' })
    res.end(JSON.stringify({ error: err.statusCode ? `${err}` : 'An unexpected error occurred' }))
  }

  const placeholders = (arr, shift = 0) => arr.map((_, i) => `$${i + 1 + shift}`).join(', ');

  const streamFrom = (id, req, output, attachCloseHandler, needsFiltering = false) => {
    log.verbose(req.requestId, `Starting stream from ${id} for ${req.accountId}`)

    const listener = message => {
      const { event, payload, queued_at } = JSON.parse(message)

      const transmit = () => {
        const now   = new Date().getTime()
        const delta = now - queued_at;

        log.silly(req.requestId, `Transmitting for ${req.accountId}: ${event} ${payload} Delay: ${delta}ms`)
        output(event, payload)
      }

      // Only messages that may require filtering are statuses, since notifications
      // are already personalized and deletes do not matter
      if (needsFiltering && event === 'update') {
        pgPool.connect((err, client, done) => {
          if (err) {
            log.error(err)
            return
          }

          const unpackedPayload  = JSON.parse(payload)
          const targetAccountIds = [unpackedPayload.account.id].concat(unpackedPayload.mentions.map(item => item.id)).concat(unpackedPayload.reblog ? [unpackedPayload.reblog.account.id] : [])

          client.query(`SELECT target_account_id FROM blocks WHERE account_id = $1 AND target_account_id IN (${placeholders(targetAccountIds, 1)}) UNION SELECT target_account_id FROM mutes WHERE account_id = $1 AND target_account_id IN (${placeholders(targetAccountIds, 1)})`, [req.accountId].concat(targetAccountIds), (err, result) => {
            done()

            if (err) {
              log.error(err)
              return
            }

            if (result.rows.length > 0) {
              return
            }

            transmit()
          })
        })
      } else {
        transmit()
      }
    }

    subscribe(id, listener)
    attachCloseHandler(id, listener)
  }

  // Setup stream output to HTTP
  const streamToHttp = (req, res) => {
    res.setHeader('Content-Type', 'text/event-stream')
    res.setHeader('Transfer-Encoding', 'chunked')

    const heartbeat = setInterval(() => res.write(':thump\n'), 15000)

    req.on('close', () => {
      log.verbose(req.requestId, `Ending stream for ${req.accountId}`)
      clearInterval(heartbeat)
    })

    return (event, payload) => {
      res.write(`event: ${event}\n`)
      res.write(`data: ${payload}\n\n`)
    }
  }

  // Setup stream end for HTTP
  const streamHttpEnd = req => (id, listener) => {
    req.on('close', () => {
      unsubscribe(id, listener)
    })
  }

  // Setup stream output to WebSockets
  const streamToWs = (req, ws) => {
    const heartbeat = setInterval(() => ws.ping(), 15000)

    ws.on('close', () => {
      log.verbose(req.requestId, `Ending stream for ${req.accountId}`)
      clearInterval(heartbeat)
    })

    return (event, payload) => {
      if (ws.readyState !== ws.OPEN) {
        log.error(req.requestId, 'Tried writing to closed socket')
        return
      }

      ws.send(JSON.stringify({ event, payload }))
    }
  }

  // Setup stream end for WebSockets
  const streamWsEnd = ws => (id, listener) => {
    ws.on('close', () => {
      unsubscribe(id, listener)
    })

    ws.on('error', e => {
      unsubscribe(id, listener)
    })
  }

  app.use(setRequestId)
  app.use(allowCrossDomain)
  app.use(authenticationMiddleware)
  app.use(errorMiddleware)

  app.get('/api/v1/streaming/user', (req, res) => {
    streamFrom(`timeline:${req.accountId}`, req, streamToHttp(req, res), streamHttpEnd(req))
  })

  app.get('/api/v1/streaming/public', (req, res) => {
    streamFrom('timeline:public', req, streamToHttp(req, res), streamHttpEnd(req), true)
  })

  app.get('/api/v1/streaming/public/local', (req, res) => {
    streamFrom('timeline:public:local', req, streamToHttp(req, res), streamHttpEnd(req), true)
  })

  app.get('/api/v1/streaming/hashtag', (req, res) => {
    streamFrom(`timeline:hashtag:${req.query.tag}`, req, streamToHttp(req, res), streamHttpEnd(req), true)
  })

  app.get('/api/v1/streaming/hashtag/local', (req, res) => {
    streamFrom(`timeline:hashtag:${req.query.tag}:local`, req, streamToHttp(req, res), streamHttpEnd(req), true)
  })

  wss.on('connection', ws => {
    const location = url.parse(ws.upgradeReq.url, true)
    const token    = location.query.access_token
    const req      = { requestId: uuid.v4() }

    accountFromToken(token, req, err => {
      if (err) {
        log.error(req.requestId, err)
        ws.close()
        return
      }

      switch(location.query.stream) {
      case 'user':
        streamFrom(`timeline:${req.accountId}`, req, streamToWs(req, ws), streamWsEnd(ws))
        break;
      case 'public':
        streamFrom('timeline:public', req, streamToWs(req, ws), streamWsEnd(ws), true)
        break;
      case 'public:local':
        streamFrom('timeline:public:local', req, streamToWs(req, ws), streamWsEnd(ws), true)
        break;
      case 'hashtag':
        streamFrom(`timeline:hashtag:${location.query.tag}`, req, streamToWs(req, ws), streamWsEnd(ws), true)
        break;
      case 'hashtag:local':
        streamFrom(`timeline:hashtag:${location.query.tag}:local`, req, streamToWs(req, ws), streamWsEnd(ws), true)
        break;
      default:
        ws.close()
      }
    })
  })

  server.listen(process.env.PORT || 4000, () => {
    log.level = process.env.LOG_LEVEL || 'verbose'
    log.info(`Starting streaming API server worker on ${server.address().address}:${server.address().port}`)
  })

  process.on('SIGINT', exit)
  process.on('SIGTERM', exit)
  process.on('exit', exit)

  function exit() {
    server.close()
  }
}