docs: function (context, next) {
          this._cache.read(context.cached._id, function (err, doc) {
              if (err || !doc)
                  return next(err || new Error('Critical failure! A cache entry has mysteriously disappeared...'));
              context.cached = doc;
              // this should happen only for internal phantom errors, not client javascript errors.
              if (context.cached.error) {
                  this.logger.warn('The last try gave us an error, try to recompute.', { error: context.cached.error });
                  context.options.force = true;
                  context.options.wait = true;
              }
              next(null);
          });
      }