1) Using a single compression context for the whole stream means you have to keep that context active on the client and server while the connection is active. This may have a nontrivial memory cost, especially at high compression levels. (Don't set the compression window any larger than it needs to be!)
2) Using a single context also means that you can't decompress one frame without having read the whole stream that led up to that. This prevents some possible useful optimizations if you're "fanning out" messages to many recipients - if you're compressing each message individually, you can compress it once and send the same compressed message to every recipient.
It sounds like these contexts should be cleared when they reach a certain memory limit, or maybe reset periodically, i.e every N messages. Is there another way to manage the memory cost?
Many compression standards include memory limits, to guarantee compatibility, and the older the standard the lower that limit is likely to be. If the standards didn't dictate this stuff, DVD sellers could release a DVD that needed a 4MB decompression window, and it'd fail to play on players that only had 2MB of memory - setting a standard and following it avoids this happening.
We used a streaming compression format that was originally designed for IBM tape drives.
It was fast as hell and worked really well, and was gentle on CPU and it was easy to control memory usage.
In the early 2000s on a modest 2-proc AMD64 machine we ran out of fast Ethernet way before we felt CPU pressure.
We got hit by the SOAP mafia during Longhorn; we couldn’t convince the web services to adopt it; instead they made us enshittify our “2 bytes length, 2 bytes msgtype, structs-on-the-wire” speed demon with their XML crap.
https://www.ietf.org/archive/id/draft-ietf-httpbis-compressi...
lambdaloop•1mo ago
duskwuff•1mo ago
dgoldstein0•1mo ago
dgoldstein0•1mo ago
gkbrk•1mo ago
There is RFC 9220 [2] that makes WebSockets go over QUIC (which is UDP-based). But that's still expected to expose a stream of bytes to the WebSocket, which still keeps the ordering guarantee.
[1]: https://datatracker.ietf.org/doc/html/rfc6455
[2]: https://datatracker.ietf.org/doc/rfc9220/