code: public function waitReady()
      {
          $x = 0;
          while ($x++ < 100) {
              usleep(self::WAIT_IDLE);
              if ($this[self::STARTED_MARKER] === true) {
                  return $this;
              }
          }
  
          throw new \RuntimeException('Wait process running timeout for child pid ' . $this->getPid());
      }
docs: Wait Process is completely initialized.
  
  @return $this;
  
  @limitation This method should not to be called from child process.
  @throw \RuntimeException If time out occurred during wait;