等待带有内部回调的同步函数

Question

我有几个同步函数，其中一些不是我自己的代码。 这些函数在完成时接受并执行回调函数。

我需要等到这些回调完成后再退出应用程序。 我该如何执行？

const serverGracefulShutdown = () => {

  logger.info('Signal received: Gracefully killing application');

  httpServer.close(() => {
    logger.info('Apollo server closed');
  });

  redis.quit(() => {
    logger.info('Redis client closed');
  });

  stopKafkaConsumer(() => {
    logger.info('Kafka consumer closed');
  });

  logger.info('Application closed');
  process.exit(0);
};

process.on('SIGINT', serverGracefulShutdown);
process.on('SIGTERM', serverGracefulShutdown);

在上面的代码中，我想确保应用程序正常关闭。

所有正在运行的东西都停止了，然后我可以调用 process.exit(0)。

Answer 1

你应该可以玩 Promise：

const serverGracefulShutdown = () => {

  logger.info('Signal received: Gracefully killing application');

  const promises = [

    new Promise((resolve, reject) => httpServer.close(() => {
      // do you get an optional error param inside this callback?
      // if yes, then "if (error) reject(error) else resolve()"
      // (or any other way to mark this operation as failed)
      logger.info('Apollo server closed');
      resolve();
    })),

    new Promise((resolve /* + reject? */) => redis.close(() => {
      logger.info('Redis client closed');
      resolve();
    })),

    new Promise((resolve /* + reject? */) => stopKafkaConsumer(() => {
      logger.info('Kafka consumer closed');
      resolve();
    }))

  ];

  return Promise.all(promises).then(() => {
    logger.info('Application closed');
    process.exit(0);
  }).catch((error) => {
    // what's your plan if at least one failed?
  });

};

process.on('SIGINT', serverGracefulShutdown);
process.on('SIGTERM', serverGracefulShutdown);