Upstream with multiple request reply
mdounin at mdounin.ru
Mon Jan 16 22:17:23 UTC 2012
On Mon, Jan 16, 2012 at 10:45:58PM +0100, Bertrand Paquet wrote:
> Arg, it's not a good news :)
> Do you think I can do ngx_http_subrequest to do some additional request to
> back end ?
> How to say to nginx to wait for subrequest before calling create_request ?
If you are ok with *independent* requests to backend (that is, you
just need to requests two happen, but don't need to implement some
complex protocol), than using subrequests is right way to go.
See e.g. addition filter module sources for simple subrequest
usage example, or ssi module sources for more complex one.
> On Mon, Jan 16, 2012 at 22:20, Maxim Dounin <mdounin at mdounin.ru> wrote:
> > Hello!
> > On Mon, Jan 16, 2012 at 09:40:26PM +0100, Bertrand Paquet wrote:
> > > Hi all,
> > >
> > > I'm trying to write an upstream which have to do multiple request / reply
> > > with backend, for one frontend request.
> > >
> > > Currently,
> > > - I'm writing first request to backend in create_request handler, write
> > > data into r->upstream->request_bufs, and returning NGX_OK
> > > - Nginx call me on process_header. I can read data from
> > > r->upstream->buffer. I can loop on process_header if I return NGX_AGAIN.
> > > But I'm not able to send more data to backend. I try to add buffer in
> > > r->upstream->request_bufs, in r->upstream->request_bufs->next, nothing
> > work.
> > >
> > > Anybody know how to send data to backend in the process_header callback ?
> > The upstream module is designed to handle "single request - single
> > response" model, it's not capable of sending multiple requests to
> > backend.
> > Maxim Dounin
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