index.ts

import { defaults, noop } from "../utils/lodash";
import { inherits } from "util";
import { EventEmitter } from "events";
import Deque = require("denque");
import Command from "../command";
import Commander from "../commander";
import {
  isInt,
  CONNECTION_CLOSED_ERROR_MSG,
  parseURL,
  Debug,
  resolveTLSProfile,
} from "../utils";
import asCallback from "standard-as-callback";
import * as eventHandler from "./event_handler";
import { StandaloneConnector, SentinelConnector } from "../connectors";
import ScanStream from "../ScanStream";
import * as commands from "redis-commands";
import * as PromiseContainer from "../promiseContainer";
import { addTransactionSupport } from "../transaction";
import {
  IRedisOptions,
  ReconnectOnError,
  DEFAULT_REDIS_OPTIONS,
} from "./RedisOptions";
import { NetStream, CallbackFunction, ICommandItem } from "../types";

const debug = Debug("redis");

/**
 * Creates a Redis instance
 *
 * @constructor
 * @param {(number|string|Object)} [port=6379] - Port of the Redis server,
 * or a URL string(see the examples below),
 * or the `options` object(see the third argument).
 * @param {string|Object} [host=localhost] - Host of the Redis server,
 * when the first argument is a URL string,
 * this argument is an object represents the options.
 * @param {Object} [options] - Other options.
 * @param {number} [options.port=6379] - Port of the Redis server.
 * @param {string} [options.host=localhost] - Host of the Redis server.
 * @param {string} [options.family=4] - Version of IP stack. Defaults to 4.
 * @param {string} [options.path=null] - Local domain socket path. If set the `port`,
 * `host` and `family` will be ignored.
 * @param {number} [options.keepAlive=0] - TCP KeepAlive on the socket with a X ms delay before start.
 * Set to a non-number value to disable keepAlive.
 * @param {boolean} [options.noDelay=true] - Whether to disable the Nagle's Algorithm. By default we disable
 * it to reduce the latency.
 * @param {string} [options.connectionName=null] - Connection name.
 * @param {number} [options.db=0] - Database index to use.
 * @param {string} [options.password=null] - If set, client will send AUTH command
 * with the value of this option when connected.
 * @param {string} [options.username=null] - Similar to `password`, Provide this for Redis ACL support.
 * @param {boolean} [options.dropBufferSupport=false] - Drop the buffer support for better performance.
 * This option is recommended to be enabled when
 * handling large array response and you don't need the buffer support.
 * @param {boolean} [options.enableReadyCheck=true] - When a connection is established to
 * the Redis server, the server might still be loading the database from disk.
 * While loading, the server not respond to any commands.
 * To work around this, when this option is `true`,
 * ioredis will check the status of the Redis server,
 * and when the Redis server is able to process commands,
 * a `ready` event will be emitted.
 * @param {boolean} [options.enableOfflineQueue=true] - By default,
 * if there is no active connection to the Redis server,
 * commands are added to a queue and are executed once the connection is "ready"
 * (when `enableReadyCheck` is `true`,
 * "ready" means the Redis server has loaded the database from disk, otherwise means the connection
 * to the Redis server has been established). If this option is false,
 * when execute the command when the connection isn't ready, an error will be returned.
 * @param {number} [options.connectTimeout=10000] - The milliseconds before a timeout occurs during the initial
 * connection to the Redis server.
 * @param {boolean} [options.autoResubscribe=true] - After reconnected, if the previous connection was in the
 * subscriber mode, client will auto re-subscribe these channels.
 * @param {boolean} [options.autoResendUnfulfilledCommands=true] - If true, client will resend unfulfilled
 * commands(e.g. block commands) in the previous connection when reconnected.
 * @param {boolean} [options.lazyConnect=false] - By default,
 * When a new `Redis` instance is created, it will connect to Redis server automatically.
 * If you want to keep the instance disconnected until a command is called, you can pass the `lazyConnect` option to
 * the constructor:
 *
 * ```javascript
 * var redis = new Redis({ lazyConnect: true });
 * // No attempting to connect to the Redis server here.

 * // Now let's connect to the Redis server
 * redis.get('foo', function () {
 * });
 * ```
 * @param {Object} [options.tls] - TLS connection support. See https://github.com/luin/ioredis#tls-options
 * @param {string} [options.keyPrefix=''] - The prefix to prepend to all keys in a command.
 * @param {function} [options.retryStrategy] - See "Quick Start" section
 * @param {number} [options.maxRetriesPerRequest] - See "Quick Start" section
 * @param {number} [options.maxLoadingRetryTime=10000] - when redis server is not ready, we will wait for
 * `loading_eta_seconds` from `info` command or maxLoadingRetryTime (milliseconds), whichever is smaller.
 * @param {function} [options.reconnectOnError] - See "Quick Start" section
 * @param {boolean} [options.readOnly=false] - Enable READONLY mode for the connection.
 * Only available for cluster mode.
 * @param {boolean} [options.stringNumbers=false] - Force numbers to be always returned as JavaScript
 * strings. This option is necessary when dealing with big numbers (exceed the [-2^53, +2^53] range).
 * @param {boolean} [options.enableTLSForSentinelMode=false] - Whether to support the `tls` option
 * when connecting to Redis via sentinel mode.
 * @param {NatMap} [options.natMap=null] NAT map for sentinel connector.
 * @param {boolean} [options.updateSentinels=true] - Update the given `sentinels` list with new IP
 * addresses when communicating with existing sentinels.
 * @param {boolean} [options.failoverDetector=false] - Detect failover actively by subscribing to the
 * related channels. With this option disabled, ioredis is still able to detect failovers because Redis
 * Sentinel will disconnect all clients whenever a failover happens, so ioredis will reconnect to the new
 * master. This option is useful when you want to detect failover quicker, but it will create more TCP
 * connections to Redis servers in order to subscribe to related channels.
* @param {boolean} [options.enableAutoPipelining=false] - When enabled, all commands issued during an event loop
 * iteration are automatically wrapped in a pipeline and sent to the server at the same time.
 * This can dramatically improve performance.
 * @param {string[]} [options.autoPipeliningIgnoredCommands=[]] - The list of commands which must not be automatically wrapped in pipelines.
 * @param {number} [options.maxScriptsCachingTime=60000] Default script definition caching time.
  * @extends [EventEmitter](http://nodejs.org/api/events.html#events_class_events_eventemitter)
 * @extends Commander
 * @example
 * ```js
 * var Redis = require('ioredis');
 *
 * var redis = new Redis();
 *
 * var redisOnPort6380 = new Redis(6380);
 * var anotherRedis = new Redis(6380, '192.168.100.1');
 * var unixSocketRedis = new Redis({ path: '/tmp/echo.sock' });
 * var unixSocketRedis2 = new Redis('/tmp/echo.sock');
 * var urlRedis = new Redis('redis://user:password@redis-service.com:6379/');
 * var urlRedis2 = new Redis('//localhost:6379');
 * var urlRedisTls = new Redis('rediss://user:password@redis-service.com:6379/');
 * var authedRedis = new Redis(6380, '192.168.100.1', { password: 'password' });
 * ```
 */
export default Redis;
function Redis(port: number, host: string, options: IRedisOptions): void;
function Redis(path: string, options: IRedisOptions): void;
function Redis(port: number, options: IRedisOptions): void;
function Redis(port: number, host: string): void;
function Redis(options: IRedisOptions): void;
function Redis(port: number): void;
function Redis(path: string): void;
function Redis(): void;
function Redis() {
  if (!(this instanceof Redis)) {
    console.error(
      new Error(
        "Calling `Redis()` like a function is deprecated. Using `new Redis()` instead."
      ).stack.replace("Error", "Warning")
    );
    return new Redis(arguments[0], arguments[1], arguments[2]);
  }

  this.parseOptions(arguments[0], arguments[1], arguments[2]);

  EventEmitter.call(this);
  Commander.call(this);

  this.resetCommandQueue();
  this.resetOfflineQueue();

  this.connectionEpoch = 0;

  if (this.options.Connector) {
    this.connector = new this.options.Connector(this.options);
  } else if (this.options.sentinels) {
    const sentinelConnector = new SentinelConnector(this.options);
    sentinelConnector.emitter = this;

    this.connector = sentinelConnector;
  } else {
    this.connector = new StandaloneConnector(this.options);
  }

  this.retryAttempts = 0;

  // Prepare a cache of scripts and setup a interval which regularly clears it
  this._addedScriptHashes = {};

  // Prepare autopipelines structures
  this._autoPipelines = new Map();
  this._runningAutoPipelines = new Set();

  Object.defineProperty(this, "autoPipelineQueueSize", {
    get() {
      let queued = 0;

      for (const pipeline of this._autoPipelines.values()) {
        queued += pipeline.length;
      }

      return queued;
    },
  });

  // end(or wait) -> connecting -> connect -> ready -> end
  if (this.options.lazyConnect) {
    this.setStatus("wait");
  } else {
    this.connect().catch(noop);
  }
}

inherits(Redis, EventEmitter);
Object.assign(Redis.prototype, Commander.prototype);

/**
 * Create a Redis instance
 *
 * @deprecated
 */
// @ts-ignore
Redis.createClient = function (...args): Redis {
  // @ts-ignore
  return new Redis(...args);
};

/**
 * Default options
 *
 * @var defaultOptions
 * @private
 */
Redis.defaultOptions = DEFAULT_REDIS_OPTIONS;

Redis.prototype.resetCommandQueue = function () {
  this.commandQueue = new Deque();
};

Redis.prototype.resetOfflineQueue = function () {
  this.offlineQueue = new Deque();
};

Redis.prototype.parseOptions = function () {
  this.options = {};
  let isTls = false;
  for (let i = 0; i < arguments.length; ++i) {
    const arg = arguments[i];
    if (arg === null || typeof arg === "undefined") {
      continue;
    }
    if (typeof arg === "object") {
      defaults(this.options, arg);
    } else if (typeof arg === "string") {
      defaults(this.options, parseURL(arg));
      if (arg.startsWith("rediss://")) {
        isTls = true;
      }
    } else if (typeof arg === "number") {
      this.options.port = arg;
    } else {
      throw new Error("Invalid argument " + arg);
    }
  }
  if (isTls) {
    defaults(this.options, { tls: true });
  }
  defaults(this.options, Redis.defaultOptions);

  if (typeof this.options.port === "string") {
    this.options.port = parseInt(this.options.port, 10);
  }
  if (typeof this.options.db === "string") {
    this.options.db = parseInt(this.options.db, 10);
  }
  if (this.options.parser === "hiredis") {
    console.warn(
      "Hiredis parser is abandoned since ioredis v3.0, and JavaScript parser will be used"
    );
  }

  this.options = resolveTLSProfile(this.options);
};

/**
 * Change instance's status
 * @private
 */
Redis.prototype.setStatus = function (status, arg) {
  // @ts-ignore
  if (debug.enabled) {
    debug(
      "status[%s]: %s -> %s",
      this._getDescription(),
      this.status || "[empty]",
      status
    );
  }
  this.status = status;
  process.nextTick(this.emit.bind(this, status, arg));
};

Redis.prototype.clearAddedScriptHashesCleanInterval = function () {
  if (this._addedScriptHashesCleanInterval) {
    clearInterval(this._addedScriptHashesCleanInterval);
    this._addedScriptHashesCleanInterval = null;
  }
};

/**
 * Create a connection to Redis.
 * This method will be invoked automatically when creating a new Redis instance
 * unless `lazyConnect: true` is passed.
 *
 * When calling this method manually, a Promise is returned, which will
 * be resolved when the connection status is ready.
 * @param {function} [callback]
 * @return {Promise<void>}
 * @public
 */
Redis.prototype.connect = function (callback) {
  const _Promise = PromiseContainer.get();
  const promise = new _Promise<void>((resolve, reject) => {
    if (
      this.status === "connecting" ||
      this.status === "connect" ||
      this.status === "ready"
    ) {
      reject(new Error("Redis is already connecting/connected"));
      return;
    }

    // Make sure only one timer is active at a time
    this.clearAddedScriptHashesCleanInterval();

    // Scripts need to get reset on reconnect as redis
    // might have been restarted or some failover happened
    this._addedScriptHashes = {};

    // Start the script cache cleaning
    this._addedScriptHashesCleanInterval = setInterval(() => {
      this._addedScriptHashes = {};
    }, this.options.maxScriptsCachingTime);

    this.connectionEpoch += 1;
    this.setStatus("connecting");

    const { options } = this;

    this.condition = {
      select: options.db,
      auth: options.username
        ? [options.username, options.password]
        : options.password,
      subscriber: false,
    };

    const _this = this;
    asCallback(
      this.connector.connect(function (type, err) {
        _this.silentEmit(type, err);
      }) as Promise<NetStream>,
      function (err: Error | null, stream?: NetStream) {
        if (err) {
          _this.flushQueue(err);
          _this.silentEmit("error", err);
          reject(err);
          _this.setStatus("end");
          return;
        }
        let CONNECT_EVENT = options.tls ? "secureConnect" : "connect";
        if (options.sentinels && !options.enableTLSForSentinelMode) {
          CONNECT_EVENT = "connect";
        }

        _this.stream = stream;
        if (typeof options.keepAlive === "number") {
          stream.setKeepAlive(true, options.keepAlive);
        }

        if (stream.connecting) {
          stream.once(CONNECT_EVENT, eventHandler.connectHandler(_this));

          if (options.connectTimeout) {
            /*
             * Typically, Socket#setTimeout(0) will clear the timer
             * set before. However, in some platforms (Electron 3.x~4.x),
             * the timer will not be cleared. So we introduce a variable here.
             *
             * See https://github.com/electron/electron/issues/14915
             */
            let connectTimeoutCleared = false;
            stream.setTimeout(options.connectTimeout, function () {
              if (connectTimeoutCleared) {
                return;
              }
              stream.setTimeout(0);
              stream.destroy();

              const err = new Error("connect ETIMEDOUT");
              // @ts-ignore
              err.errorno = "ETIMEDOUT";
              // @ts-ignore
              err.code = "ETIMEDOUT";
              // @ts-ignore
              err.syscall = "connect";
              eventHandler.errorHandler(_this)(err);
            });
            stream.once(CONNECT_EVENT, function () {
              connectTimeoutCleared = true;
              stream.setTimeout(0);
            });
          }
        } else if (stream.destroyed) {
          const firstError = _this.connector.firstError;
          if (firstError) {
            process.nextTick(() => {
              eventHandler.errorHandler(_this)(firstError);
            });
          }
          process.nextTick(eventHandler.closeHandler(_this));
        } else {
          process.nextTick(eventHandler.connectHandler(_this));
        }
        if (!stream.destroyed) {
          stream.once("error", eventHandler.errorHandler(_this));
          stream.once("close", eventHandler.closeHandler(_this));
        }

        if (options.noDelay) {
          stream.setNoDelay(true);
        }

        const connectionReadyHandler = function () {
          _this.removeListener("close", connectionCloseHandler);
          resolve();
        };
        var connectionCloseHandler = function () {
          _this.removeListener("ready", connectionReadyHandler);
          reject(new Error(CONNECTION_CLOSED_ERROR_MSG));
        };
        _this.once("ready", connectionReadyHandler);
        _this.once("close", connectionCloseHandler);
      }
    );
  });

  return asCallback(promise, callback);
};

/**
 * Disconnect from Redis.
 *
 * This method closes the connection immediately,
 * and may lose some pending replies that haven't written to client.
 * If you want to wait for the pending replies, use Redis#quit instead.
 * @public
 */
Redis.prototype.disconnect = function (reconnect) {
  this.clearAddedScriptHashesCleanInterval();

  if (!reconnect) {
    this.manuallyClosing = true;
  }
  if (this.reconnectTimeout && !reconnect) {
    clearTimeout(this.reconnectTimeout);
    this.reconnectTimeout = null;
  }
  if (this.status === "wait") {
    eventHandler.closeHandler(this)();
  } else {
    this.connector.disconnect();
  }
};

/**
 * Disconnect from Redis.
 *
 * @deprecated
 */
Redis.prototype.end = function () {
  this.disconnect();
};

/**
 * Create a new instance with the same options as the current one.
 *
 * @example
 * ```js
 * var redis = new Redis(6380);
 * var anotherRedis = redis.duplicate();
 * ```
 *
 * @public
 */
Redis.prototype.duplicate = function (override: IRedisOptions) {
  return new Redis(Object.assign({}, this.options, override || {}));
};

Redis.prototype.recoverFromFatalError = function (
  commandError,
  err: Error | null,
  options
) {
  this.flushQueue(err, options);
  this.silentEmit("error", err);
  this.disconnect(true);
};

Redis.prototype.handleReconnection = function handleReconnection(
  err: Error,
  item: ICommandItem
) {
  let needReconnect: ReturnType<ReconnectOnError> = false;
  if (this.options.reconnectOnError) {
    needReconnect = this.options.reconnectOnError(err);
  }

  switch (needReconnect) {
    case 1:
    case true:
      if (this.status !== "reconnecting") {
        this.disconnect(true);
      }
      item.command.reject(err);
      break;
    case 2:
      if (this.status !== "reconnecting") {
        this.disconnect(true);
      }
      if (
        this.condition.select !== item.select &&
        item.command.name !== "select"
      ) {
        this.select(item.select);
      }
      this.sendCommand(item.command);
      break;
    default:
      item.command.reject(err);
  }
};

/**
 * Flush offline queue and command queue with error.
 *
 * @param {Error} error - The error object to send to the commands
 * @param {object} options
 * @private
 */
Redis.prototype.flushQueue = function (error: Error, options: IRedisOptions) {
  options = defaults({}, options, {
    offlineQueue: true,
    commandQueue: true,
  });

  let item;
  if (options.offlineQueue) {
    while (this.offlineQueue.length > 0) {
      item = this.offlineQueue.shift();
      item.command.reject(error);
    }
  }

  if (options.commandQueue) {
    if (this.commandQueue.length > 0) {
      if (this.stream) {
        this.stream.removeAllListeners("data");
      }
      while (this.commandQueue.length > 0) {
        item = this.commandQueue.shift();
        item.command.reject(error);
      }
    }
  }
};

/**
 * Check whether Redis has finished loading the persistent data and is able to
 * process commands.
 *
 * @param {Function} callback
 * @private
 */
Redis.prototype._readyCheck = function (callback: CallbackFunction) {
  const _this = this;
  this.info(function (err: Error | null, res: string) {
    if (err) {
      return callback(err);
    }
    if (typeof res !== "string") {
      return callback(null, res);
    }

    const info: { [key: string]: any } = {};

    const lines = res.split("\r\n");
    for (let i = 0; i < lines.length; ++i) {
      const [fieldName, ...fieldValueParts] = lines[i].split(":");
      const fieldValue = fieldValueParts.join(":");
      if (fieldValue) {
        info[fieldName] = fieldValue;
      }
    }

    if (!info.loading || info.loading === "0") {
      callback(null, info);
    } else {
      const loadingEtaMs = (info.loading_eta_seconds || 1) * 1000;
      const retryTime =
        _this.options.maxLoadingRetryTime &&
        _this.options.maxLoadingRetryTime < loadingEtaMs
          ? _this.options.maxLoadingRetryTime
          : loadingEtaMs;
      debug("Redis server still loading, trying again in " + retryTime + "ms");
      setTimeout(function () {
        _this._readyCheck(callback);
      }, retryTime);
    }
  });
};

/**
 * Emit only when there's at least one listener.
 *
 * @param {string} eventName - Event to emit
 * @param {...*} arguments - Arguments
 * @return {boolean} Returns true if event had listeners, false otherwise.
 * @private
 */
Redis.prototype.silentEmit = function (eventName) {
  let error;
  if (eventName === "error") {
    error = arguments[1];

    if (this.status === "end") {
      return;
    }

    if (this.manuallyClosing) {
      // ignore connection related errors when manually disconnecting
      if (
        error instanceof Error &&
        (error.message === CONNECTION_CLOSED_ERROR_MSG ||
          // @ts-ignore
          error.syscall === "connect" ||
          // @ts-ignore
          error.syscall === "read")
      ) {
        return;
      }
    }
  }
  if (this.listeners(eventName).length > 0) {
    return this.emit.apply(this, arguments);
  }
  if (error && error instanceof Error) {
    console.error("[ioredis] Unhandled error event:", error.stack);
  }
  return false;
};

/**
 * Listen for all requests received by the server in real time.
 *
 * This command will create a new connection to Redis and send a
 * MONITOR command via the new connection in order to avoid disturbing
 * the current connection.
 *
 * @param {function} [callback] The callback function. If omit, a promise will be returned.
 * @example
 * ```js
 * var redis = new Redis();
 * redis.monitor(function (err, monitor) {
 *   // Entering monitoring mode.
 *   monitor.on('monitor', function (time, args, source, database) {
 *     console.log(time + ": " + util.inspect(args));
 *   });
 * });
 *
 * // supports promise as well as other commands
 * redis.monitor().then(function (monitor) {
 *   monitor.on('monitor', function (time, args, source, database) {
 *     console.log(time + ": " + util.inspect(args));
 *   });
 * });
 * ```
 * @public
 */
Redis.prototype.monitor = function (callback) {
  const monitorInstance = this.duplicate({
    monitor: true,
    lazyConnect: false,
  });

  const Promise = PromiseContainer.get();
  return asCallback(
    new Promise(function (resolve) {
      monitorInstance.once("monitoring", function () {
        resolve(monitorInstance);
      });
    }),
    callback
  );
};

addTransactionSupport(Redis.prototype);

/**
 * Send a command to Redis
 *
 * This method is used internally by the `Redis#set`, `Redis#lpush` etc.
 * Most of the time you won't invoke this method directly.
 * However when you want to send a command that is not supported by ioredis yet,
 * this command will be useful.
 *
 * @method sendCommand
 * @memberOf Redis#
 * @param {Command} command - The Command instance to send.
 * @see {@link Command}
 * @example
 * ```js
 * var redis = new Redis();
 *
 * // Use callback
 * var get = new Command('get', ['foo'], 'utf8', function (err, result) {
 *   console.log(result);
 * });
 * redis.sendCommand(get);
 *
 * // Use promise
 * var set = new Command('set', ['foo', 'bar'], 'utf8');
 * set.promise.then(function (result) {
 *   console.log(result);
 * });
 * redis.sendCommand(set);
 * ```
 * @private
 */
Redis.prototype.sendCommand = function (command: Command, stream: NetStream) {
  if (this.status === "wait") {
    this.connect().catch(noop);
  }
  if (this.status === "end") {
    command.reject(new Error(CONNECTION_CLOSED_ERROR_MSG));
    return command.promise;
  }
  if (
    this.condition.subscriber &&
    !Command.checkFlag("VALID_IN_SUBSCRIBER_MODE", command.name)
  ) {
    command.reject(
      new Error(
        "Connection in subscriber mode, only subscriber commands may be used"
      )
    );
    return command.promise;
  }

  if (typeof this.options.commandTimeout === "number") {
    command.setTimeout(this.options.commandTimeout);
  }

  if (command.name === "quit") {
    this.clearAddedScriptHashesCleanInterval();
  }

  let writable =
    this.status === "ready" ||
    (!stream &&
      this.status === "connect" &&
      commands.exists(command.name) &&
      commands.hasFlag(command.name, "loading"));
  if (!this.stream) {
    writable = false;
  } else if (!this.stream.writable) {
    writable = false;
  } else if (this.stream._writableState && this.stream._writableState.ended) {
    // https://github.com/iojs/io.js/pull/1217
    writable = false;
  }

  if (!writable && !this.options.enableOfflineQueue) {
    command.reject(
      new Error(
        "Stream isn't writeable and enableOfflineQueue options is false"
      )
    );
    return command.promise;
  }

  if (!writable && command.name === "quit" && this.offlineQueue.length === 0) {
    this.disconnect();
    command.resolve(Buffer.from("OK"));
    return command.promise;
  }

  if (writable) {
    // @ts-ignore
    if (debug.enabled) {
      debug(
        "write command[%s]: %d -> %s(%o)",
        this._getDescription(),
        this.condition.select,
        command.name,
        command.args
      );
    }
    (stream || this.stream).write(command.toWritable());

    this.commandQueue.push({
      command: command,
      stream: stream,
      select: this.condition.select,
    });

    if (Command.checkFlag("WILL_DISCONNECT", command.name)) {
      this.manuallyClosing = true;
    }
  } else if (this.options.enableOfflineQueue) {
    // @ts-ignore
    if (debug.enabled) {
      debug(
        "queue command[%s]: %d -> %s(%o)",
        this._getDescription(),
        this.condition.select,
        command.name,
        command.args
      );
    }
    this.offlineQueue.push({
      command: command,
      stream: stream,
      select: this.condition.select,
    });
  }

  if (command.name === "select" && isInt(command.args[0])) {
    const db = parseInt(command.args[0], 10);
    if (this.condition.select !== db) {
      this.condition.select = db;
      this.emit("select", db);
      debug("switch to db [%d]", this.condition.select);
    }
  }

  return command.promise;
};

/**
 * Get description of the connection. Used for debugging.
 * @private
 */
Redis.prototype._getDescription = function () {
  let description;
  if (this.options.path) {
    description = this.options.path;
  } else if (
    this.stream &&
    this.stream.remoteAddress &&
    this.stream.remotePort
  ) {
    description = this.stream.remoteAddress + ":" + this.stream.remotePort;
  } else {
    description = this.options.host + ":" + this.options.port;
  }
  if (this.options.connectionName) {
    description += ` (${this.options.connectionName})`;
  }
  return description;
};
[
  "scan",
  "sscan",
  "hscan",
  "zscan",
  "scanBuffer",
  "sscanBuffer",
  "hscanBuffer",
  "zscanBuffer",
].forEach(function (command) {
  Redis.prototype[command + "Stream"] = function (key, options) {
    if (command === "scan" || command === "scanBuffer") {
      options = key;
      key = null;
    }
    return new ScanStream(
      defaults(
        {
          objectMode: true,
          key: key,
          redis: this,
          command: command,
        },
        options
      )
    );
  };
});