一次修改一个文件

Question

我使用 JSON 文件作为数据库，所以我需要在文件尚未完全更新时消除 read/write 错误。

如何从同一文件创建更新进程队列？

（我正在使用打字稿）

Answer 1

您可以使用bull，它是一个经过良好测试的第三方队列库。你可以使用 npm 安装它：

npm install bull --save

要添加类型运行这个：

npm install @types/bull --save-dev

您可以按照以下步骤操作：

const Queue = require('bull');

const videoQueue = new Queue('video transcoding', 'redis://127.0.0.1:6379');
const audioQueue = new Queue('audio transcoding', { redis: { port: 6379, host: '127.0.0.1', password: 'foobared' } }); // Specify Redis connection using object
const imageQueue = new Queue('image transcoding');
const pdfQueue = new Queue('pdf transcoding');

videoQueue.process(function (job, done) {

  // job.data contains the custom data passed when the job was created
  // job.id contains id of this job.

  // transcode video asynchronously and report progress
  job.progress(42);

  // call done when finished
  done();

  // or give a error if error
  done(new Error('error transcoding'));

  // or pass it a result
  done(null, { framerate: 29.5 /* etc... */ });

  // If the job throws an unhandled exception it is also handled correctly
  throw new Error('some unexpected error');
});

audioQueue.process(function (job, done) {
  // transcode audio asynchronously and report progress
  job.progress(42);

  // call done when finished
  done();

  // or give a error if error
  done(new Error('error transcoding'));

  // or pass it a result
  done(null, { samplerate: 48000 /* etc... */ });

  // If the job throws an unhandled exception it is also handled correctly
  throw new Error('some unexpected error');
});

imageQueue.process(function (job, done) {
  // transcode image asynchronously and report progress
  job.progress(42);

  // call done when finished
  done();

  // or give a error if error
  done(new Error('error transcoding'));

  // or pass it a result
  done(null, { width: 1280, height: 720 /* etc... */ });

  // If the job throws an unhandled exception it is also handled correctly
  throw new Error('some unexpected error');
});

pdfQueue.process(function (job) {
  // Processors can also return promises instead of using the done callback
  return pdfAsyncProcessor();
});

videoQueue.add({ video: 'http://example.com/video1.mov' });
audioQueue.add({ audio: 'http://example.com/audio1.mp3' });
imageQueue.add({ image: 'http://example.com/image1.tiff' });

你可以查看bull的文档来实现它。

注意：如果你不明白如何实现它，我建议你关注this链接。