code: function log(key, result, done) {
      var storage = this;
      
      // store result as JSON serialized string
      result = JSON.stringify(result);
  
      // generate result key from task key
      key = key + "-result";
      
      // first add the key to the log
      this.redis().rpush(this.logKey(), key, function(err) {
          if (err) done(err);
  
          // now store result data
          else storage.redis().set(key, result, done);
      });
  }
docs: Log task result.
  @param {string} key
  @param {object} result
  @param {function} done