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unpipe() and resume() in _transform() #31190
Description
- Node.js Version: 13.*
- OS: mac
- Scope (install, code, runtime, meta, other?):
- Module (and version) (if relevant):
In case of synchronous pipe removal in _transform, the resume method does not resume as expected
const stream = require('stream')
const fs = require('fs');
const readStream = fs.createReadStream('big.txt')
const writeStream = fs.createWriteStream('result.txt');
const transformStream = new class extends stream.Transform {
_transform(chunk, encoding, callback) {
readStream.unpipe()
readStream.resume()
}
}
readStream.on('end', () => {
console.log('never print')
})
readStream
.pipe(transformStream)
.pipe(writeStream)Nevertheless, resume operation during an asynchronous call and removal not from the _transform method
Can someone explain this behavior why unpipe () and resume () do not work in the _transform method?
Activity
addaleax commentedon Jan 5, 2020
/cc @ronag
ronag commentedon Jan 5, 2020
ronag commentedon Jan 5, 2020
addaleax commentedon Jan 5, 2020
@ronag The only two things I could think of are a) process.exit() or equivalents being called or b) blocking JS execution that prevents the nextTick queue from running.
For debugging Node.js core, it’s sometimes a good idea to use
process._rawDebug()rather thanconsole.log(), which doesn’t use streams under the hood.That being said, if I just add the
console.log()calls like you did, it does print output for me.ronag commentedon Jan 5, 2020
Oh, thanks for that! I'll keep digging.
stream: sync stream unpipe resume
stream: sync stream unpipe resume
stream: sync stream unpipe resume
stream: sync stream unpipe resume
stream: sync stream unpipe resume