body filter redirect

[Dk Jack]

Hello Maxim,
Thanks for responding. Can I get some clarification on what you mean by the
statement below:

"More flexibility can be achieved by reading the request body
earlier - for example, you can do this from your own module, or
with embedded scripting such as perl or njs."

Are you suggesting that I use ngx_http_read_client_request_body api in my
module?

http://nginx.org/en/docs/dev/development_guide.html#http_request_body

I had similar trouble using that API with redirection. Are there some
tricks to getting
it to work when using that API? Are there any reference implementations
doing
redirection after inspecting the request body?
Thanks for your help!

Dk.

> Hello!
> It is generally too late to do any actions like "change the
> upstream/location etc" based on the body content, as the request
> body is usually read only when the location is already known and
> the upstream name is already obtained. Also consider
> "proxy_request_buffering off;" - reading the request body implies
> that nginx is sending the request body to the backend as well.
> That is, you can't really do more than modifying the request body
> or rejecting the request completely.
>
> You may, however, provide some variables from your body request
> body filter - and, if it's possible in your particular
> configuration, use these variables to do some conditional
> processing.
>
> Note thought that conditional processing needs to happen after the
> request body is read. As such, it is usually quite limited,
> especially when using standard modules, since the request body is
> usually read last.
>
> For example, with proxy the request body is read after the
> variables in the "proxy_pass" directive are evaluated, so even
> with "proxy_request_buffering on;" (the default) you cannot use
> the variables from your request body filter module to change the
> upstream. You can, however, use it to control headers in the
> upstream request by using "proxy_set_header" with appropriate
> variables (again, assuming buffered request body reading - for
> obvious reasons this won't work with "proxy_request_buffering
> off;").
>
> More flexibility can be achieved by reading the request body
> earlier - for example, you can do this from your own module, or
> with embedded scripting such as perl or njs.
>
> --
> Maxim Dounin
> http://mdounin.ru/
> _______________________________________________
> nginx-devel mailing list
> nginx-devel at nginx.org
> http://mailman.nginx.org/mailman/listinfo/nginx-devel
>
On Mon, Jul 12, 2021 at 12:47 PM Dk Jack <dnj0496 at gmail.com> wrote:

> Hi,
> In my module, I am trying to take actions based on the content of the
> body. To accomplish this, I am capturing the body using body file as shown
> in the example below:
>
>
> http://mdounin.ru/hg/ngx_http_catch_body_filter_module/file/tip/ngx_http_catch_body_filter_module.c
>
> This is working well. I can inspect the contents of the body and take
> different actions like rejecting requests etc. However, one of the actions
> I want to do is redirect the request based on the body content i.e if the
> content contains some string etc, then redirect the request i.e change the
> upstream/location etc. My question is, is it even possible to redirect a
> request in the body filter stage? Is there another way to do body
> capture/filter and still be able to redirect the request after inspecting
> the body? Any help, suggestions or sample code is appreciated. Thanks.
>
> Dk.
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.nginx.org/pipermail/nginx-devel/attachments/20210713/2399eceb/attachment-0001.htm>