Re: [hybi] Payload only compression extension, again

[John Tamplin <[e-mail]>]

On Tue, Jul 26, 2011 at 10:23 AM, Takeshi Yoshino <[e-mail]>wrote:

> Additionally, I'd like to propose one more parameter.
>
> - No compression context sharing option
> -- though I'm claiming that compression context sharing across frames is
> good, it's sometimes harmful for intermediaries
> -- for load balancers that dispatches WebSocket frames to different
> backends, shared compression context means that the load balancer have to
> perform decompression. it's burden in terms of both memory pressure and CPU
> power.
> -- So, I'd add parameter "finish_at_eof" to allow such intermediaries to
> ask clients not to keep using the same compression context across frames
>

The problem is that if you don't share compression state across frames, then
it becomes critical to not try and compress incompressible content.  Look at
the experiment data I presented in that same thread -- it is very easy for
frame sizes to go up if you aren't sharing compression state, so I think if
this option is included we have to decide now how to turn off compression on
a frame-by-frame basis rather than delaying it for a future extension.  In
contrast, if compression state is maintained across frames, it is still
usually a win even on incompressible content because different frames have
redundancy, and the loss is never bad.

I would prefer, for the initial version, to simply have load balancers that
can't maintain compression state to simply refuse compression.

-- 
John A. Tamplin
Software Engineer (GWT), Google