[dev] http phase handler

[Igor Sysoev]

On Wed, Dec 05, 2007 at 07:54:54PM +0100, Manlio Perillo wrote:

> Igor Sysoev ha scritto:
> >On Wed, Dec 05, 2007 at 06:32:23PM +0100, Manlio Perillo wrote:
> >
> >>I'm interested in how HTTP phases handlers works in nginx.
> >>
> >>I would like to add support, in mod_wsgi, to NGX_HTTP_PREACCESS_PHASE, 
> >>NGX_HTTP_ACCESS_PHASE and NGX_HTTP_CONTENT_PHASE.
> >>
> >>I'm reading the sources but I'm not sure to understand how a phase 
> >>handler terminates.
> >>
> >>With a request handler, the handler can return NGX_DONE and then call 
> >>ngx_http_finalize_request, but what about a phase handler?
> >
> >All phase handlers should simpy return value
> >NGX_OK/NGX_DECLINED/NGX_HTTP_FORBIDDEN/etc.
> >
> 
> Ok.
> 
> >In the context phase there may run a single defined content handler (perl,
> >proxy_pass, fastcgi_pass, memcached_pass, flv, empty_gif) or stack
> >of handlers: index, autoindex, dav, static.
> >
> >If a defined handler calls finally ngx_http_finalize_request(NGX_DECLINED),
> >then nginx goes to the stack of handlers. Now only perl can do this.
> >
> 
> Ok.
> This should be possible with Python, too.
> But I can't see an useful application for this.

For example, perl may handle POSTs and decline other to default stack.

> >The preaccess phase is for generic handlers:
> >on NGX_OK it goes to a next phase,
> >on NGX_DECLINED it goes to a next handler in the same phase,
> >on NGX_AGAIN/NGX_DONE it simply return,
> >on NGX_ERROR or NGX_HTTP_... it calls ngx_http_finalize_request()
> >
> >The access phase is special to handle NGX_OK/NGX_DECLINED depending on
> >satisfy_any. However, I'm going to change it, because now:
> >
> >     location / {
> >         satisfy_any  on;
> >         auth_basic ...
> >         # no allow/deny rules
> >     }
> >
> >does not ask username/password.
> >
> 
> 
> Is it possible to return NGX_DONE/NGX_AGAIN from the access phase 
> handler and then call ngx_http_finalize_request(NGX_HTTP_...) when the 
> handler is done (as an example it may setup the events when doing an 
> asynchronous query to a database)?

Yes. However, I could not say right how you should finalize processing
after second call: ngx_http_finalize_request() or return.

> The only module with a phase handler that does "interesting" things is 
> the autoindex module, but it uses sub requests (and I have yet to 
> understand how they works :)).

The stock autoindex module does not use subrequests.


-- 
Igor Sysoev
http://sysoev.ru/en/