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Piping a simple program to stdout gives "MaxListenersExceededWarning: Possible EventEmitter memory leak detected when" #16767
Description
- Version: v8.9.0
- Platform: Linux brunhilde 4.13.8-1-ARCH deps: update openssl to 1.0.1j #1 SMP PREEMPT Wed Oct 18 11:49:44 CEST 2017 x86_64 GNU/Linux
- Subsystem: console.js
When running a program that produces a lot of output that is consumed by another program in the pipeline, Node gives memory leak errors.
To reproduce try saving this simple program:
// save as bug.js
for (var i = 0; i < 10000; i++) {
console.log('line ' + i)
}Then run
node bug.js | less
And quit less (type q). This results in the following warning being printed out:
(node:31009) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 error listeners added. Use emitter.setMaxListeners() to increase limit
@mcollina mentioned it is most likely a bug here, https://github.com/nodejs/node/blob/master/lib/console.js#L91-L119
(In general it would be useful as well if the memory leak errors printed out a stack trace so it was easier to hunt down the causes)
Activity
mscdex commentedon Nov 5, 2017
You mean
--trace-warnings?addaleax commentedon Nov 5, 2017
Fwiw, I couldn’t reproduce this with master or with v8.9.0… but yes,
--trace-warningsshould give a good hint at what’s going on.mscdex commentedon Nov 5, 2017
I'm also not able to reproduce this on Linux.
mcollina commentedon Nov 5, 2017
I think it's this block: https://github.com/nodejs/node/blob/master/lib/console.js#L81-L87.
What I think is happening is that there are a bunch of writes that are about to error, and we add a lot of
'error'in the meanwhile.mcollina commentedon Nov 5, 2017
I can reproduce it on Mac OS X, you just need to wait some seconds before hitting
qwithin less.mcollina commentedon Nov 5, 2017
My fix is working, I'll send a PR soon.
mafintosh commentedon Nov 5, 2017
@mscdex I'm also on linux and can reproduce.
--trace-warningssolves it for me but when other users report a memleak or you get a hard to reproduce one it would be nice if a stack happened per default.mafintosh commentedon Nov 8, 2017
Thanks for the quick turnaround everyone :)
console: avoid adding infinite error listeners
console: avoid adding infinite error listeners
console: avoid adding infinite error listeners