Use ESM with Streaming API Server

streaming/constants.mjs

@@ -0,0 +1,27 @@
+// @ts-check
+
+import * as os from 'node:os';
+
+/** @type {boolean} */
+export const alwaysRequireAuth =
+  process.env.LIMITED_FEDERATION_MODE === 'true' ||
+  process.env.WHITELIST_MODE === 'true' ||
+  process.env.AUTHORIZED_FETCH === 'true';
+
+/** @type {string} */
+export const env = process.env.NODE_ENV || 'development';
+
+/** @type {string} */
+export const logLevel = process.env.LOG_LEVEL || 'verbose';
+
+/** @type {number} */
+export const numWorkers =
+  +process.env.STREAMING_CLUSTER_NUM ||
+  (env === 'development' ? 1 : Math.max(os.cpus().length - 1, 1));
+
+/** @type {string} */
+export const redisNamespace = process.env.REDIS_NAMESPACE || null;
+
+export const trustedProxyIp = process.env.TRUSTED_PROXY_IP
+  ? process.env.TRUSTED_PROXY_IP.split(/(?:\s*,\s*|\s+)/)
+  : 'loopback,uniquelocal';

streaming/index.mjs

@@ -1,112 +1,51 @@
 // @ts-check
 
-const os = require('os');
+import * as http from 'node:http';
-const throng = require('throng');
+import * as url from 'node:url';
-const dotenv = require('dotenv');
-const express = require('express');
-const http = require('http');
-const redis = require('redis');
-const pg = require('pg');
-const log = require('npmlog');
-const url = require('url');
-const uuid = require('uuid');
-const fs = require('fs');
-const WebSocket = require('ws');
 
-const env = process.env.NODE_ENV || 'development';
+import * as dotenv from 'dotenv';
-const alwaysRequireAuth = process.env.LIMITED_FEDERATION_MODE === 'true' || process.env.WHITELIST_MODE === 'true' || process.env.AUTHORIZED_FETCH === 'true';
+import express from 'express';
+import log from 'npmlog';
+import * as pg from 'pg';
+import throng from 'throng';
+import * as uuid from 'uuid';
+import WebSocket from 'ws';
+
+import {
+  alwaysRequireAuth,
+  env,
+  logLevel,
+  numWorkers,
+  redisNamespace,
+  trustedProxyIp,
+} from './constants.mjs';
+import {
+  allowCrossDomain,
+  authenticationMiddleware,
+  errorMiddleware,
+  setRemoteAddress,
+  setRequestId,
+} from './middlewares.mjs';
+import Subscriber from './subscriber.mjs';
+import {
+  attachServerWithConfig,
+  checkScopes,
+  dbUrlToConfig,
+  firstParam,
+  httpNotFound,
+  isInScope,
+  isTruthy,
+  onPortAvailable,
+  parseJSON,
+  placeholders,
+  redisUrlToClient,
+} from './utils.mjs';
 
 dotenv.config({
   path: env === 'production' ? '.env.production' : '.env',
 });
 
-log.level = process.env.LOG_LEVEL || 'verbose';
+log.level = logLevel;
-
-/**
- * @param {string} dbUrl
- * @return {Object.<string, any>}
- */
-const dbUrlToConfig = (dbUrl) => {
-  if (!dbUrl) {
-    return {};
-  }
-
-  const params = url.parse(dbUrl, true);
-  const config = {};
-
-  if (params.auth) {
-    [config.user, config.password] = params.auth.split(':');
-  }
-
-  if (params.hostname) {
-    config.host = params.hostname;
-  }
-
-  if (params.port) {
-    config.port = params.port;
-  }
-
-  if (params.pathname) {
-    config.database = params.pathname.split('/')[1];
-  }
-
-  const ssl = params.query && params.query.ssl;
-
-  if (ssl && ssl === 'true' || ssl === '1') {
-    config.ssl = true;
-  }
-
-  return config;
-};
-
-/**
- * @param {Object.<string, any>} defaultConfig
- * @param {string} redisUrl
- */
-const redisUrlToClient = async (defaultConfig, redisUrl) => {
-  const config = defaultConfig;
-
-  let client;
-
-  if (!redisUrl) {
-    client = redis.createClient(config);
-  } else if (redisUrl.startsWith('unix://')) {
-    client = redis.createClient(Object.assign(config, {
-      socket: {
-        path: redisUrl.slice(7),
-      },
-    }));
-  } else {
-    client = redis.createClient(Object.assign(config, {
-      url: redisUrl,
-    }));
-  }
-
-  client.on('error', (err) => log.error('Redis Client Error!', err));
-  await client.connect();
-
-  return client;
-};
-
-const numWorkers = +process.env.STREAMING_CLUSTER_NUM || (env === 'development' ? 1 : Math.max(os.cpus().length - 1, 1));
-
-/**
- * @param {string} json
- * @param {any} req
- * @return {Object.<string, any>|null}
- */
-const parseJSON = (json, req) => {
-  try {
-    return JSON.parse(json);
-  } catch (err) {
-    if (req.accountId) {
-      log.warn(req.requestId, `Error parsing message from user ${req.accountId}: ${err}`);
-    } else {
-      log.silly(req.requestId, `Error parsing message from ${req.remoteAddress}: ${err}`);
-    }
-    return null;
-  }
-};
 
 const startMaster = () => {
   if (!process.env.SOCKET && process.env.PORT && isNaN(+process.env.PORT)) {
@@ -119,13 +58,14 @@ const startMaster = () => {
 const startWorker = async (workerId) => {
   log.warn(`Starting worker ${workerId}`);
 
+  /** @type {Record<string, pg.PoolConfig>} */
   const pgConfigs = {
     development: {
       user:     process.env.DB_USER || pg.defaults.user,
       password: process.env.DB_PASS || pg.defaults.password,
       database: process.env.DB_NAME || 'mastodon_development',
       host:     process.env.DB_HOST || pg.defaults.host,
-      port:     process.env.DB_PORT || pg.defaults.port,
+      port:     process.env.DB_PORT ? +process.env.DB_PORT : pg.defaults.port,
       max:      10,
     },
 
@@ -134,7 +74,7 @@ const startWorker = async (workerId) => {
       password: process.env.DB_PASS || '',
       database: process.env.DB_NAME || 'mastodon_production',
       host:     process.env.DB_HOST || 'localhost',
-      port:     process.env.DB_PORT || 5432,
+      port:     process.env.DB_PORT ? +process.env.DB_PORT : 5432,
       max:      10,
     },
   };
@@ -146,34 +86,31 @@ const startWorker = async (workerId) => {
 
   const app = express();
 
-  app.set('trust proxy', process.env.TRUSTED_PROXY_IP ? process.env.TRUSTED_PROXY_IP.split(/(?:\s*,\s*|\s+)/) : 'loopback,uniquelocal');
+  app.set('trust proxy', trustedProxyIp);
 
-  const pgPool = new pg.Pool(Object.assign(pgConfigs[env], dbUrlToConfig(process.env.DATABASE_URL)));
+  const pgPool = new pg.Pool({
+    ...pgConfigs[env],
+    ...dbUrlToConfig(process.env.DATABASE_URL),
+  });
   const server = http.createServer(app);
-  const redisNamespace = process.env.REDIS_NAMESPACE || null;
 
+  /** @type {import('redis').RedisClientOptions} */
   const redisParams = {
     socket: {
       host: process.env.REDIS_HOST || '127.0.0.1',
-      port: process.env.REDIS_PORT || 6379,
+      port: process.env.REDIS_PORT ? +process.env.REDIS_PORT : 6379,
     },
-    database: process.env.REDIS_DB || 0,
+    database: process.env.REDIS_DB ? +process.env.REDIS_DB : 0,
     password: process.env.REDIS_PASSWORD || undefined,
   };
 
-  if (redisNamespace) {
-    redisParams.namespace = redisNamespace;
-  }
-
   const redisPrefix = redisNamespace ? `${redisNamespace}:` : '';
 
-  /**
-   * @type {Object.<string, Array.<function(string): void>>}
-   */
-  const subs = {};
-
   const redisSubscribeClient = await redisUrlToClient(redisParams, process.env.REDIS_URL);
   const redisClient = await redisUrlToClient(redisParams, process.env.REDIS_URL);
+  const subscriber = new Subscriber({
+    redisClient: redisSubscribeClient,
+  });
 
   /**
    * @param {string[]} channels
@@ -195,121 +132,6 @@ const startWorker = async (workerId) => {
     };
   };
 
-  /**
-   * @param {string} message
-   * @param {string} channel
-   */
-  const onRedisMessage = (message, channel) => {
-    const callbacks = subs[channel];
-
-    log.silly(`New message on channel ${channel}`);
-
-    if (!callbacks) {
-      return;
-    }
-
-    callbacks.forEach(callback => callback(message));
-  };
-
-  /**
-   * @param {string} channel
-   * @param {function(string): void} callback
-   */
-  const subscribe = (channel, callback) => {
-    log.silly(`Adding listener for ${channel}`);
-
-    subs[channel] = subs[channel] || [];
-
-    if (subs[channel].length === 0) {
-      log.verbose(`Subscribe ${channel}`);
-      redisSubscribeClient.subscribe(channel, onRedisMessage);
-    }
-
-    subs[channel].push(callback);
-  };
-
-  /**
-   * @param {string} channel
-   */
-  const unsubscribe = (channel, callback) => {
-    log.silly(`Removing listener for ${channel}`);
-
-    if (!subs[channel]) {
-      return;
-    }
-
-    subs[channel] = subs[channel].filter(item => item !== callback);
-
-    if (subs[channel].length === 0) {
-      log.verbose(`Unsubscribe ${channel}`);
-      redisSubscribeClient.unsubscribe(channel);
-      delete subs[channel];
-    }
-  };
-
-  const FALSE_VALUES = [
-    false,
-    0,
-    '0',
-    'f',
-    'F',
-    'false',
-    'FALSE',
-    'off',
-    'OFF',
-  ];
-
-  /**
-   * @param {any} value
-   * @return {boolean}
-   */
-  const isTruthy = value =>
-    value && !FALSE_VALUES.includes(value);
-
-  /**
-   * @param {any} req
-   * @param {any} res
-   * @param {function(Error=): void}
-   */
-  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();
-  };
-
-  /**
-   * @param {any} req
-   * @param {any} res
-   * @param {function(Error=): void}
-   */
-  const setRequestId = (req, res, next) => {
-    req.requestId = uuid.v4();
-    res.header('X-Request-Id', req.requestId);
-
-    next();
-  };
-
-  /**
-   * @param {any} req
-   * @param {any} res
-   * @param {function(Error=): void}
-   */
-  const setRemoteAddress = (req, res, next) => {
-    req.remoteAddress = req.connection.remoteAddress;
-
-    next();
-  };
-
-  /**
-   * @param {any} req
-   * @param {string[]} necessaryScopes
-   * @return {boolean}
-   */
-  const isInScope = (req, necessaryScopes) =>
-    req.scopes.some(scope => necessaryScopes.includes(scope));
-
   /**
    * @param {string} token
    * @param {any} req
@@ -409,58 +231,6 @@ const startWorker = async (workerId) => {
     }
   };
 
-  const PUBLIC_CHANNELS = [
-    'public',
-    'public:media',
-    'public:local',
-    'public:local:media',
-    'public:remote',
-    'public:remote:media',
-    'hashtag',
-    'hashtag:local',
-  ];
-
-  /**
-   * @param {any} req
-   * @param {string} channelName
-   * @return {Promise.<void>}
-   */
-  const checkScopes = (req, channelName) => new Promise((resolve, reject) => {
-    log.silly(req.requestId, `Checking OAuth scopes for ${channelName}`);
-
-    // When accessing public channels, no scopes are needed
-    if (PUBLIC_CHANNELS.includes(channelName)) {
-      resolve();
-      return;
-    }
-
-    // The `read` scope has the highest priority, if the token has it
-    // then it can access all streams
-    const requiredScopes = ['read'];
-
-    // When accessing specifically the notifications stream,
-    // we need a read:notifications, while in all other cases,
-    // we can allow access with read:statuses. Mind that the
-    // user stream will not contain notifications unless
-    // the token has either read or read:notifications scope
-    // as well, this is handled separately.
-    if (channelName === 'user:notification') {
-      requiredScopes.push('read:notifications');
-    } else {
-      requiredScopes.push('read:statuses');
-    }
-
-    if (req.scopes && requiredScopes.some(requiredScope => req.scopes.includes(requiredScope))) {
-      resolve();
-      return;
-    }
-
-    const err = new Error('Access token does not cover required scopes');
-    err.status = 401;
-
-    reject(err);
-  });
-
   /**
    * @param {any} info
    * @param {function(boolean, number, string): void} callback
@@ -507,73 +277,6 @@ const startWorker = async (workerId) => {
     };
   };
 
-  /**
-   * @param {any} req
-   * @param {any} res
-   */
-  const subscribeHttpToSystemChannel = (req, res) => {
-    const systemChannelId = `timeline:access_token:${req.accessTokenId}`;
-
-    const listener = createSystemMessageListener(req, {
-
-      onKill() {
-        res.end();
-      },
-
-    });
-
-    res.on('close', () => {
-      unsubscribe(`${redisPrefix}${systemChannelId}`, listener);
-    });
-
-    subscribe(`${redisPrefix}${systemChannelId}`, listener);
-  };
-
-  /**
-   * @param {any} req
-   * @param {any} res
-   * @param {function(Error=): void} next
-   */
-  const authenticationMiddleware = (req, res, next) => {
-    if (req.method === 'OPTIONS') {
-      next();
-      return;
-    }
-
-    accountFromRequest(req, alwaysRequireAuth).then(() => checkScopes(req, channelNameFromPath(req))).then(() => {
-      subscribeHttpToSystemChannel(req, res);
-    }).then(() => {
-      next();
-    }).catch(err => {
-      next(err);
-    });
-  };
-
-  /**
-   * @param {Error} err
-   * @param {any} req
-   * @param {any} res
-   * @param {function(Error=): void} next
-   */
-  const errorMiddleware = (err, req, res, next) => {
-    log.error(req.requestId, err.toString());
-
-    if (res.headersSent) {
-      next(err);
-      return;
-    }
-
-    res.writeHead(err.status || 500, { 'Content-Type': 'application/json' });
-    res.end(JSON.stringify({ error: err.status ? err.toString() : 'An unexpected error occurred' }));
-  };
-
-  /**
-   * @param {array} arr
-   * @param {number=} shift
-   * @return {string}
-   */
-  const placeholders = (arr, shift = 0) => arr.map((_, i) => `$${i + 1 + shift}`).join(', ');
-
   /**
    * @param {string} listId
    * @param {any} req
@@ -690,7 +393,7 @@ const startWorker = async (workerId) => {
     };
 
     ids.forEach(id => {
-      subscribe(`${redisPrefix}${id}`, listener);
+      subscriber.register(`${redisPrefix}${id}`, listener);
     });
 
     if (attachCloseHandler) {
@@ -735,7 +438,7 @@ const startWorker = async (workerId) => {
   const streamHttpEnd = (req, closeHandler = undefined) => (ids) => {
     req.on('close', () => {
       ids.forEach(id => {
-        unsubscribe(id);
+        subscriber.unregister(id);
       });
 
       if (closeHandler) {
@@ -759,14 +462,6 @@ const startWorker = async (workerId) => {
     ws.send(JSON.stringify({ stream: streamName, event, payload }));
   };
 
-  /**
-   * @param {any} res
-   */
-  const httpNotFound = res => {
-    res.writeHead(404, { 'Content-Type': 'application/json' });
-    res.end(JSON.stringify({ error: 'Not found' }));
-  };
-
   app.use(setRequestId);
   app.use(setRemoteAddress);
   app.use(allowCrossDomain);
@@ -780,7 +475,8 @@ const startWorker = async (workerId) => {
   app.use(errorMiddleware);
 
   app.get('/api/v1/streaming/*', (req, res) => {
-    channelNameToIds(req, channelNameFromPath(req), req.query).then(({ channelIds, options }) => {
+    channelNameToIds(req, channelNameFromPath(req), req.query)
+      .then(({ channelIds, options }) => {
         const onSend = streamToHttp(req, res);
         const onEnd = streamHttpEnd(req, subscriptionHeartbeat(channelIds));
 
@@ -994,7 +690,7 @@ const startWorker = async (workerId) => {
       const { listener, stopHeartbeat } = subscription;
 
       channelIds.forEach(channelId => {
-        unsubscribe(`${redisPrefix}${channelId}`, listener);
+        subscriber.unregister(`${redisPrefix}${channelId}`, listener);
       });
 
       stopHeartbeat();
@@ -1019,7 +715,7 @@ const startWorker = async (workerId) => {
 
     });
 
-    subscribe(`${redisPrefix}${systemChannelId}`, listener);
+    subscriber.register(`${redisPrefix}${systemChannelId}`, listener);
 
     subscriptions[systemChannelId] = {
       listener,
@@ -1028,18 +724,6 @@ const startWorker = async (workerId) => {
     };
   };
 
-  /**
-   * @param {string|string[]} arrayOrString
-   * @return {string}
-   */
-  const firstParam = arrayOrString => {
-    if (Array.isArray(arrayOrString)) {
-      return arrayOrString[0];
-    } else {
-      return arrayOrString;
-    }
-  };
-
   wss.on('connection', (ws, req) => {
     const location = url.parse(req.url, true);
 
@@ -1068,7 +752,7 @@ const startWorker = async (workerId) => {
         const { listener, stopHeartbeat } = session.subscriptions[channelIds];
 
         channelIds.split(';').forEach(channelId => {
-          unsubscribe(`${redisPrefix}${channelId}`, listener);
+          subscriber.unregister(`${redisPrefix}${channelId}`, listener);
         });
 
         stopHeartbeat();
@@ -1135,45 +819,6 @@ const startWorker = async (workerId) => {
   process.on('uncaughtException', onError);
 };
 
-/**
- * @param {any} server
- * @param {function(string): void} [onSuccess]
- */
-const attachServerWithConfig = (server, onSuccess) => {
-  if (process.env.SOCKET || process.env.PORT && isNaN(+process.env.PORT)) {
-    server.listen(process.env.SOCKET || process.env.PORT, () => {
-      if (onSuccess) {
-        fs.chmodSync(server.address(), 0o666);
-        onSuccess(server.address());
-      }
-    });
-  } else {
-    server.listen(+process.env.PORT || 4000, process.env.BIND || '127.0.0.1', () => {
-      if (onSuccess) {
-        onSuccess(`${server.address().address}:${server.address().port}`);
-      }
-    });
-  }
-};
-
-/**
- * @param {function(Error=): void} onSuccess
- */
-const onPortAvailable = onSuccess => {
-  const testServer = http.createServer();
-
-  testServer.once('error', err => {
-    onSuccess(err);
-  });
-
-  testServer.once('listening', () => {
-    testServer.once('close', () => onSuccess());
-    testServer.close();
-  });
-
-  attachServerWithConfig(testServer);
-};
-
 onPortAvailable(err => {
   if (err) {
     log.error('Could not start server, the port or socket is in use');

streaming/middlewares.mjs

@@ -0,0 +1,62 @@
+// @ts-check
+
+import log from 'npmlog';
+import * as uuid from 'uuid';
+
+import { alwaysRequireAuth } from './constants.mjs';
+import { checkScopes } from './utils.mjs';
+
+/** @type {import('express').RequestHandler} */
+export function 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();
+}
+
+/** @type {import('express').RequestHandler} */
+export function authenticationMiddleware(req, res, next) {
+  if (req.method === 'OPTIONS') {
+    next();
+    return;
+  }
+
+  accountFromRequest(req, alwaysRequireAuth)
+    .then(() => checkScopes(req, channelNameFromPath(req)))
+    .then(() => {
+      subscribeHttpToSystemChannel(req, res);
+    }).then(() => {
+      next();
+    }).catch(err => {
+      next(err);
+    });
+}
+
+/** @type {import('express').ErrorRequestHandler} */
+export function errorMiddleware(err, req, res, next) {
+  log.error(req.requestId, err.toString());
+
+  if (res.headersSent) {
+    next(err);
+    return;
+  }
+
+  res.writeHead(err.status || 500, { 'Content-Type': 'application/json' });
+  res.end(JSON.stringify({ error: err.status ? err.toString() : 'An unexpected error occurred' }));
+}
+
+/** @type {import('express').RequestHandler} */
+export function setRemoteAddress(req, _res, next) {
+  req.remoteAddress = req.connection.remoteAddress;
+
+  next();
+}
+
+/** @type {import('express').RequestHandler} */
+export function setRequestId(req, res, next) {
+  req.requestId = uuid.v4();
+  res.header('X-Request-Id', req.requestId);
+
+  next();
+}

streaming/subscriber.mjs

@@ -0,0 +1,88 @@
+// @ts-check
+
+import log from 'npmlog';
+
+const LOG_PREFIX = 'subscriber';
+
+/**
+ * @typedef SubscriberOptions
+ * @property {import('redis').RedisClientType} redisClient
+ */
+
+/**
+ * @callback SubscribeListener
+ * @param {string} message
+ */
+
+export default class Subscriber {
+
+  /**
+   * @param {SubscriberOptions} options
+   */
+  constructor({ redisClient }) {
+    /** @type {import('redis').RedisClientType} */
+    this.redisClient = redisClient;
+
+    /** @type {Map<string, Set<SubscribeListener>>} */
+    this.subs = new Map();
+  }
+
+  /**
+   * @param {string} message
+   * @param {string} channel
+   * @returns {void}
+   */
+  handleRedisMessage = (message, channel) => {
+    log.silly(LOG_PREFIX, `New message on channel ${channel}`);
+
+    if (this.subs.has(channel)) {
+      for (const listener of this.subs.get(channel)) {
+        listener.call(this, message);
+      }
+    }
+  };
+
+  /**
+   * @param {string} channel
+   * @param {SubscribeListener} listener
+   * @returns {void}
+   */
+  register(channel, listener) {
+    log.silly(LOG_PREFIX, `Adding listener for ${channel}`);
+
+    if (this.subs.has(channel)) {
+      this.subs.set(channel, new Set());
+    }
+
+    if (this.subs.get(channel).size < 1) {
+      log.verbose(LOG_PREFIX, `Subscribe ${channel}`);
+      this.redisClient.subscribe(channel, this.handleRedisMessage);
+    }
+
+    this.subs.get(channel).add(listener);
+  }
+
+  /**
+   * @param {string} channel
+   * @param {SubscribeListener=} listener
+   * @returns {void}
+   */
+  unregister(channel, listener) {
+    log.silly(LOG_PREFIX, `Removing listener for ${channel}`);
+
+    if (!this.subs.has(channel)) {
+      return;
+    }
+
+    if (typeof listener === 'function') {
+      this.subs.get(channel).delete(listener);
+    }
+
+    if (this.subs.get(channel).size < 1) {
+      log.verbose(LOG_PREFIX, `Unsubscribe ${channel}`);
+      this.redisClient.unsubscribe(channel);
+      this.subs.delete(channel);
+    }
+  }
+
+}

streaming/utils.mjs

@@ -0,0 +1,272 @@
+// @ts-check
+
+import * as fs from 'node:fs';
+import * as http from 'node:http';
+
+import log from 'npmlog';
+import * as redis from 'redis';
+
+const LOG_PREFIX = 'utils';
+
+/**
+ * @param {http.Server} server
+ * @param {((address: string) => void)=} onSuccess
+ * @returns {void}
+ */
+export function attachServerWithConfig(server, onSuccess) {
+  if (process.env.SOCKET || process.env.PORT && isNaN(+process.env.PORT)) {
+    server.listen(process.env.SOCKET || process.env.PORT, () => {
+      if (!onSuccess) return;
+
+      fs.chmodSync(server.address(), 0o666);
+      onSuccess(server.address());
+    });
+  } else {
+    server.listen(+process.env.PORT || 4000, process.env.BIND || '127.0.0.1', () => {
+      if (onSuccess) {
+        onSuccess(`${server.address().address}:${server.address().port}`);
+      }
+    });
+  }
+};
+
+const PUBLIC_CHANNELS = [
+  'public',
+  'public:media',
+  'public:local',
+  'public:local:media',
+  'public:remote',
+  'public:remote:media',
+  'hashtag',
+  'hashtag:local',
+];
+
+/**
+ * @param {import('express').Request} req
+ * @param {string} channelName
+ * @return {Promise<void>}
+ */
+export function checkScopes(req, channelName) {
+  return new Promise((resolve, reject) => {
+    log.silly(req.requestId, `Checking OAuth scopes for ${channelName}`);
+
+    // When accessing public channels, no scopes are needed
+    if (PUBLIC_CHANNELS.includes(channelName)) {
+      resolve();
+      return;
+    }
+
+    // The `read` scope has the highest priority, if the token has it
+    // then it can access all streams
+    const requiredScopes = ['read'];
+
+    // When accessing specifically the notifications stream,
+    // we need a read:notifications, while in all other cases,
+    // we can allow access with read:statuses. Mind that the
+    // user stream will not contain notifications unless
+    // the token has either read or read:notifications scope
+    // as well, this is handled separately.
+    if (channelName === 'user:notification') {
+      requiredScopes.push('read:notifications');
+    } else {
+      requiredScopes.push('read:statuses');
+    }
+
+    if (req.scopes && requiredScopes.some(requiredScope => req.scopes.includes(requiredScope))) {
+      resolve();
+      return;
+    }
+
+    const err = new Error('Access token does not cover required scopes');
+    err.status = 401;
+
+    reject(err);
+  });
+}
+
+/**
+ * @param {string} dbUrl
+ * @return {import('pg').PoolConfig}
+ */
+export function dbUrlToConfig(dbUrl) {
+  if (!dbUrl) {
+    return {};
+  }
+
+  const url = new URL(dbUrl);
+  /** @type {import('pg').PoolConfig} */
+  const config = {};
+
+  if (url.username) {
+    config.user = url.username;
+  }
+
+  if (url.password) {
+    config.password = url.password;
+  }
+
+  if (url.hostname) {
+    config.host = url.hostname;
+  }
+
+  if (url.port) {
+    config.port = +url.port;
+  }
+
+  if (url.pathname) {
+    config.database = url.pathname.split('/')[1];
+  }
+
+  if (url.searchParams.has('ssl')) {
+    config.ssl = isTruthy(url.searchParams.get('ssl'));
+  }
+
+  return config;
+}
+
+/**
+ * @param {string | string[]} arrayOrString
+ * @returns {string}
+ */
+export function firstParam(arrayOrString) {
+  return Array.isArray(arrayOrString) ? arrayOrString[0] : arrayOrString;
+}
+
+/**
+ * @param {import('express').Response} res
+ * @returns {void}
+ */
+export function httpNotFound(res) {
+  res.status(404).json({
+    error: 'Not found',
+  });
+};
+
+const FALSE_VALUES = [
+  false,
+  0,
+  '0',
+  'f',
+  'F',
+  'false',
+  'FALSE',
+  'off',
+  'OFF',
+];
+
+/**
+ * @param {import('express').Request} req
+ * @param {string[]} necessaryScopes
+ * @returns {boolean}
+ */
+export function isInScope(req, necessaryScopes) {
+  return req.scopes.some(scope => necessaryScopes.includes(scope));
+}
+
+/**
+ * @param {boolean | number | string} value
+ * @return {boolean}
+ */
+export function isTruthy(value) {
+  return value && !FALSE_VALUES.includes(value);
+}
+
+/**
+ * @param {((err?: Error) => void)=} onSuccess
+ * @returns {void}
+ */
+export function onPortAvailable(onSuccess) {
+  const testServer = http.createServer();
+
+  testServer.once('error', err => {
+    onSuccess(err);
+  });
+
+  testServer.once('listening', () => {
+    testServer.once('close', () => onSuccess());
+    testServer.close();
+  });
+
+  attachServerWithConfig(testServer);
+}
+
+/**
+ * @param {string} json
+ * @param {Express.Request} req
+ * @returns {object | null}
+ */
+export function parseJSON(json, req) {
+  try {
+    return JSON.parse(json);
+  } catch (err) {
+    if (req.accountId) {
+      log.warn(req.requestId, `Error parsing message from user ${req.accountId}:`, err);
+    } else {
+      log.silly(req.requestId, `Error parsing message from ${req.remoteAddress}:`, err);
+    }
+  }
+
+  return null;
+}
+
+/**
+ * @param {string[]} values
+ * @param {number=} shift
+ * @return {string}
+ */
+export function placeholders(values, shift = 0) {
+  return values.map((_, i) => `$${i + 1 + shift}`).join(', ');
+}
+
+/**
+ * @param {redis.RedisClientOptions} defaultConfig
+ * @param {string} redisUrl
+ * @returns {Promise<redis.RedisClientType>}
+ */
+export async function redisUrlToClient(defaultConfig, redisUrl) {
+  /** @type {redis.RedisClientType} */
+  let client;
+
+  if (!redisUrl) {
+    client = redis.createClient(defaultConfig);
+  } else if (redisUrl.startsWith('unix://')) {
+    client = redis.createClient({
+      ...defaultConfig,
+      socket: {
+        path: redisUrl.slice(7),
+      },
+    });
+  } else {
+    client = redis.createClient({
+      ...defaultConfig,
+      url: redisUrl,
+    });
+  }
+
+  client.on('error', (err) => {
+    log.error(LOG_PREFIX, 'Redis Client Error!', err);
+  });
+  await client.connect();
+
+  return client;
+}
+
+/**
+ * @param {import('express').Request} req
+ * @param {import('express').Response} res
+ */
+export function subscribeHttpToSystemChannel(req, res) {
+  const systemChannelId = `timeline:access_token:${req.accessTokenId}`;
+
+  const listener = createSystemMessageListener(req, {
+    onKill() {
+      res.end();
+    },
+  });
+
+  res.on('close', () => {
+    unsubscribe(`${redisPrefix}${systemChannelId}`, listener);
+  });
+
+  subscribe(`${redisPrefix}${systemChannelId}`, listener);
+}