how to modify response based on request using lua?

gauravphoenix · 2014-11-15T10:05:32+00:00

Hello! On Fri, Nov 14, 2014 at 1:36 PM, Daniel Holth wrote: > and this nginx config: > > https://github.com/dholth/pouchdb-bulk-get/blob/master/ngi...

how to modify response based on request using lua?

gauravphoenix

I know I can independently access request and response in lua. What I want is to access response body conditionally - and the condition is based on request. For example, if the request method is POST, then only I want to modify response (say, add header or modify body). How do I go about it?

agentzh

Hello!

On Fri, Nov 14, 2014 at 6:05 PM, Gaurav Kumar wrote:
> I know I can independently access request and response in lua. What I want
> is to access response body conditionally - and the condition is based on
> request. For example, if the request method is POST, then only I want to
> modify response (say, add header or modify body). How do I go about it?
>

header_filter_by_lua and body_filter_by_lua can be your friends here :)

But be careful about streaming processing in the body filter.

Regards,
-agentzh

gauravphoenix

Thanks Agentzh! Actually http method was just an example, I would need to conditionally process response based on post request parameters or even get request paramters. I don't think header filter will help. Anyways the bigger question is even if I can use access request filter or something similar directive, how do I combine the two directives? In other words how do I make sure body_filter_by_lua is being invoked in response to a specific request only. If someone can provide a pseudo code that would be awesome.

On Nov 14, 2014 9:49 PM, "Yichun Zhang (agentzh)" <age...@gmail.com> wrote:

Hello!

On Fri, Nov 14, 2014 at 6:05 PM, Gaurav Kumar wrote:
> I know I can independently access request and response in lua. What I want
> is to access response body conditionally - and the condition is based on
> request. For example, if the request method is POST, then only I want to
> modify response (say, add header or modify body). How do I go about it?
>

header_filter_by_lua and body_filter_by_lua can be your friends here :)

But be careful about streaming processing in the body filter.

Regards,
-agentzh.

agentzh

Hello!

On Fri, Nov 14, 2014 at 10:40 PM, Gaurav Kumar wrote:
> Thanks  Agentzh!

Please do not capitalize my nick. Thank you.

>  Actually http method was just an example, I would need to
> conditionally process response based on post request parameters or even get
> request paramters. I don't think header filter will help.

It can surely help here.

> Anyways the bigger
> question is even if I can use access request filter or something similar
> directive, how do I combine the two directives? In other words how do I make
> sure body_filter_by_lua is being invoked in response to a specific request
> only.

You can set flags in ngx.ctx in access_by_lua, for example, and make
decisions in header/body_filter_by_lua. The header/body_filter_by_lua
directives themselves are very cheap so it's totally fine that you
just check the flags in ngx.ctx and do nothing there.

Regards,
-agentzh