This could lead to memory leak of Promise/PromiseWrap

[strawhatboy]

Hello guys,

I was using this module to track what is pending in my nodejs project, and once my node process ended with heap out of memory, I was confused a lot by checking my code for memory leak...

Finally with ChromeDev tools, I found that the objects Array, Promise & PromiseWrap were always increasing without being released by GC, and they're somehow related to this module.

By checking the source code, async-hook was used to track all the Promises/async/await, and they're put into a map... so I think that's where the leak happens. and after removed require('why-is-node-running') from my code, the memory leak was gone.

So maybe I would like to recommend to put some WARNINGS in the README.md file of this module like:
if you're creating new Promises to wrap traditional callbacks a lot, this module could lead to memory leaks...

Thanks.

[mafintosh]

should be fixed by #37

[cardin]

I think this issue surfaces when using HTTPS agents with keepalive.

I'm writing a site cloner where I'm encountering a scenario with 60,000+ TLSWrap and ZLIB handlers reported. I definitely do not have that many open connections.

For larger sites, I get OOM failure. I tried removing why-is-node-running and the OOM went away.

Could it be related to this issue as well? nodejs/node#33468 I'm running Node 12.8.2.