perMessageDeflate memory leak #559

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• report a bug
• request a feature

Current behaviour

There appears to be some kind of memory leak when using perMessageDeflate: true (default).
It used to be fine, but I suppose a combination of updated dependencies (node/engine.io?) resulted in this leak. It's very noticable when it happens.

With deflate my application will use >3GB of memory (and rising until OOM) with 10-20k active websockets.
Without deflate I'm looking at <1GB. I transfer about 200-300kb of data to each client.

Here's a screenshot of what a heapdump looks like: https://i.imgur.com/byTUInU.png

Expected behaviour

Reasonable memory usage.

Setup

• OS: Linux
• engine.io: 3.2.0 and 3.1.5 (probably)
• node: v10.9.0 and at least some v9.X.X releases

Suggestion

Maybe updating "ws" to a recent version could help fix this. It would be cool if I could provide a wsEngine object directly via the options object, instead of having the require('ws') done internally.