流上的 .pipe 和管道有什么区别

Question

我在 node.js 中找到了两种不同的管道流方法

.pipe()流的众所周知的方法

https://nodejs.org/api/stream.html#stream_readable_pipe_destination_options

和流的独立功能

https://nodejs.org/api/stream.html#stream_stream_pipeline_streams_callback

我应该使用哪一个，这两者之间有什么好处？

Answer 1

TL;DR - You better want to use pipeline

What's pipeline?

From the docs: A module method to pipe between streams forwarding errors and properly cleaning up and provide a callback when the pipeline is complete.

What's the motivation for using pipeline?

? Let's take a look at the following code:

const { createReadStream } = require('fs');
const { createServer } = require('http');
const server = createServer(
  (req, res) => {
    createReadStream(__filename).pipe(res);
  }
);

server.listen(3000);

What's wrong here? If the response will quit or the client closes the connection - then the read stream is not closed or destroy which leads to a memory leak.

?So if you use pipeline, it would close all other streams and make sure that there are no memory leaks.

const { createReadStream } = require('fs');
const { createServer } = require('http');
const { pipeline } = require('stream');

const server = createServer(
  (req, res) => {
    pipeline(
      createReadStream(__filename),
      res,
      err => {
        if (err)
          console.error('Pipeline failed.', err);
        else
          console.log('Pipeline succeeded.');
      }
    );
  }
);

server.listen(3000);

Answer 2

根据文档，他们都做同样的事情。但是有一些区别：

• .pipe()是 的方法Readable，而pipeline是stream接受流到管道的模块方法。
• pipeline() 方法在管道完成时提供回调。
• pipeline()方法是从 node 10 版本开始添加的，而.pipe从最早版本的 Node.js 开始就存在。

在我看来，withpipeline()代码看起来更简洁一些，但您可以同时使用它们。

示例.pipe()：

const fs = require('fs');
const r = fs.createReadStream('file.txt');
const z = zlib.createGzip();
const w = fs.createWriteStream('file.txt.gz');
r.pipe(z).pipe(w);

示例pipeline()：

const { pipeline } = require('stream');
const fs = require('fs');
const zlib = require('zlib');

pipeline(
  fs.createReadStream('archive.tar'),
  zlib.createGzip(),
  fs.createWriteStream('archive.tar.gz'),
  (err) => {
    if (err) {
      console.error('Pipeline failed.', err);
    } else {
      console.log('Pipeline succeeded.');
    }
  }
);