feat: add maxLoadingRetryTime option when redis server not ready (#784)

And default this option to 10000ms

lib/redis.js

@@ -79,6 +79,8 @@ var PromiseContainer = require('./promiseContainer');
  * @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.
@@ -185,7 +187,8 @@ Redis.defaultOptions = {
   reconnectOnError: null,
   readOnly: false,
   stringNumbers: false,
-  maxRetriesPerRequest: 20
+  maxRetriesPerRequest: 20,
+  maxLoadingRetryTime: 10000
 };
 
 Redis.prototype.resetCommandQueue = function () {
@@ -451,7 +454,10 @@ Redis.prototype._readyCheck = function (callback) {
     if (!info.loading || info.loading === '0') {
       callback(null, info);
     } else {
-      var retryTime = (info.loading_eta_seconds || 1) * 1000;
+      var loadingEtaMs = (info.loading_eta_seconds || 1) * 1000;
+      var 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);