What's the difference between .pipe and pipeline on streams

问题

I found two different ways to pipe streams in node.js

Well known .pipe() method of a stream

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

and standalone function for streams

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

Which one should I use and what are the benefits between those two?

回答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);

回答2:

According to the documentation, they both do the same thing. But there some differences:

.pipe() is a method of Readable, while pipeline is a module method of stream that accepts streams to pipe.
pipeline() method provide a callback when the pipeline is complete.
pipeline() method was added since 10 version of node, while .pipe exist from the earliest versions of Node.

In my opinion, with pipeline() code looks a bit cleaner, but you can use both of them.

Example of .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);

Example of 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.');
    }
  }
);

来源：https://stackoverflow.com/questions/58875655/whats-the-difference-between-pipe-and-pipeline-on-streams

标签

node.js

stream