How to bind variable with connection in a customized module?

[Maxim Dounin]

Hello!

On Tue, Jan 22, 2013 at 08:16:36PM +0800, Liu Haifeng wrote:

> hi all,
> 
> I want save state during a long connection (keep-alive) for 
> performance optimization in my own HTTP handler module, thus I 
> can peek up the saved state when handling requests, to speed up 
> response. Actually it's quite like session concept. I saw 
> request struct has a member ctx, but what I want is a ctx on the 
> connection. It seems no way to save any customized variable to 
> the ngx_connection_t structure. What's the suggested way to make 
> this if I don't want the client hold something like session_id?

This was recently discussed on nginx-devel@ mailing list, and 
probably the best way currently available is to install connection 
pool cleanup handler with custom data and then iterate over 
connection pool cleanup handlers to find your data.  It is 
relatively costly, but allows to keep memory footprint from 
keepalive connections low and still allows modules to keep their 
per-connection data in rare cases when they really need to.

See here:
http://mailman.nginx.org/pipermail/nginx-devel/2012-December/003049.html

Note well though, that HTTP is stateless protocol, and the fact 
that request came from the same connection means mostly nothing: 
it might be a request from a completely different user.

-- 
Maxim Dounin
http://nginx.com/support.html