WHATWG URL Memory Leak

[aikar]

• Version: 8.9.4
• Platform: Linux 4.4.0-72-generic [stream] support piping multiple streams into a single stream #93-Ubuntu SMP Fri Mar 31 14:07:41 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
• Subsystem: url

I've been debugging this issue: sidorares/node-mysql2#726
I'm confident the leak is in native land, as my heap grew over the weekend from 21.8MB to 22.0MB, comparing Heap Snapshots with the Chrome Inspector, shows no signs of a leak.

However the RSS of my process grew 240MB (in the course of the weekend)

I've narrowed the issue down to being related to the URL parsing of the Database DSN, as when I did a core dump of my leaking process,
I found my hostnames at 1.3 million instances of the string, and thousands to hundreds of thousands of various chunks of my DSN.
mysql2 lib does url parsing like so:
https://github.com/sidorares/node-mysql2/blob/master/lib/connection_config.js#L167

Seems pretty standard to me.

edit: mysql2 notes not relevant, see below comments.

Related Issue: #17448

[aikar]

It appears the related issue I linked deals with the WHATWG impl, where as node-mysql2 is using the original implementation.

I'll see if I can swap it to the WHATWG and hopefully it will resolve it for me, but i'm a bit confused about what in the old implementation is leaking the strings since it's JS oriented.

[aikar]

It appears I am using the WHATWG version in my applications code const url = new URL(dsn); and then passing the result to node-mysql2, so the issue is at the WHATWG implementation, and not the JS one, as mysql2 isn't even doing URL parsing given that I am passing it an object form instead of string DSN.

[ChALkeR]

@aikar Could you provide a complete minimal testcase that reproduces this issue without mysql2?

[ChALkeR]

The following testcase seems to reproduce the issue on v8.9.4 but not affect v9.5.0.
@aikar Could you confirm that v9.5.0 is not affected in your setup?

const { URL } = require('url');

let i = 0;

function tick() {
  const url = 'mysql://user:pass@host/db?debug=true&charset=BIG5_CHINESE_CI&timezone=-0700&rand=' + Math.random();
  new URL(url);
  if (++i % 1e6 === 0) console.log(i);
  setImmediate(tick);
}

tick();

[TimothyGu]

Sounds like the same issue as #17448.

The fix for #17448, #17470, is included in:

• v6.13.0+ (the first v6.x version that introduced the WHATWG URL parser)
• No v8.x versions, but should be in the next v8.x version (cc @MylesBorins)
• v9.4.0+

[richardlau]

Sounds like the same issue as #17448.

The fix for #17448, #17470, is included in:

• v6.13.0+ (the first v6.x version that introduced the WHATWG URL parser)
• No v8.x versions, but should be in the next v8.x version

cc @gibfahn @nodejs/lts

[MylesBorins]

It is already staged in c2028fa and will be out in the next 8.x release --> #18336

Does it make sense to close this or wait for the release to be cut?

[aikar]

Closing as fix has landed in 8.10