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Pooled memory management currently impossible with socket.io interface #5353
Description
Is your feature request related to a problem? Please describe.
Currently, my application maintains reasonably large Buffer objects in a pool, reusing them to avoid tons of GC contention. However, socket.io is a bit of a black hole for those buffers. Once we .emit one, we don't know when it has been actually sent to the client and "released" from socket.io. Thus we cannot reuse those buffers and they must be GC. We're spending upwards of 60% of our CPU time in GC on these objects we send to socket.io right now.
Describe the solution you'd like
I would like socket.io to expose a released event that is emitted every time socket.io has successfully sent an object to the client. It would contain as its body the object that was released. These could be buffers, classes, POJO, etc., anything that lives on the heap and socket.io is now done with.
Describe alternatives you've considered
I don't see any alternatives at this time.
Additional context
I'd be very happy to implement this feature myself but before I spend time on it, I want to know that the solution I proposed is acceptable and the PR would likely to be merged.
Activity
bytenik commentedon Jun 10, 2025
@darrachequesne is this something you would be open to?
darrachequesne commentedon Jun 11, 2025
Hi!
Could the
drainevent of the low-level connection fit your use case?Reference: https://socket.io/docs/v4/server-api/#socketconn
bytenik commentedon Jun 13, 2025
@darrachequesne No; that happens when the low-level buffer that's internalized to the socket is drained. It doesn't happen when socket.io is done with the buffer because it has been placed into that TCP buffer.
bytenik commentedon Jun 16, 2025
@darrachequesne sorry to ping again and poke, but this is a huge issue at my company and I'm mostly just looking for your acknowledgement that you find my approach acceptable. At that point I'll start working on it. I would rather not develop something that then turns into a patch I have to apply to socket.io forever on my server.
darrachequesne commentedon Jun 17, 2025
Yes, that sounds like a reasonable use case 👍 could you please open a PR?
bytenik commentedon Sep 19, 2025
Hi @darrachequesne, the PR has been opened now with no engagement for several months. Can we do something to resolve this and get it merged?
darrachequesne commentedon Sep 19, 2025
Hi!
Sorry for the delay. To be honest, I think the suggested change needlessly complicates the source code, for a really specific use case, which is why I'm not sure about merging it.