Got premature close error when using pump

[Congelli501]

If you don't know about it, pump is a module to better handle stream pipe (better error handling and better close handling to prevent resource leak) https://www.npmjs.com/package/pump.
It is considered by many as safer than pipe and may be part of node core in the future (nodejs/node#13506).

mysql2 streams are not working well with pump: a "premature close" error is thrown at the end of the stream.

Here is an example code to reproduce the error:

const mysql = require('mysql2/promise');
const pump = require('pump-promise');
const {Writable} = require('stream');

/**
 * Main test function
 */
async function main () {
	const connection = await mysql.createConnection({
		/* ... */
	});

	const sqlReadable = connection.connection.query('select 1')
		.stream();

	const testWritable = new Writable({
		objectMode: true,
		write (chunk, encoding, callback) {
			console.log(chunk);
			callback();
		}
	});

	// Not working
	await pump([
		sqlReadable,
		testWritable
	]);


	// Working
	//sqlReadable.pipe(testWritable);
	//await new Promise(resolve => testWritable.on('finish', resolve));

	connection.close();
}

main()
	.then(() => console.log('ok'))
	.catch((e) => {
		process.exitCode = 1;
		console.error(e);
	});

You can uncomment the "working" code (and comment the "not working" code) to use the working pipe version.

[sidorares]

thanks for report @Congelli501 ! Have you tried to investigate what could cause that?

In the future for promise version we'll likely prefer async iterators to stream, with api similar to something like this:

for await (const row of conn.queryRows(sql)) {
  console.log(row);
}

[Congelli501]

The problem is caused by the 'close' event being emitted before the 'end' event.
Node's pipeline (https://nodejs.org/api/stream.html#stream_stream_pipeline_streams_callback) also breaks with this behaviour.

[vicary]

@Congelli501 @sidorares Sorry to bring this up again, but I think I hit the same issue.

Using for await still produces a premature close from the stream, I think it's caused by the row data still being transmitted.

Wrapping stream.emit('close'); inside a setImmediate would allow the data event to be consumed by the async generator before ending the stream, preventing the error.

Shall I open a new issue instead?

[nofarham]

@sidorares any news on this issue? We're using node 18 and getting the [ERR_STREAM_PREMATURE_CLOSE]: Premature close error.
As @vicary suggested, when wrapping stream.emit('close'); inside a setImmediate it resolves the issue.

[AnechaS]

Try upgrade mysql2 latest version. It work for me.