Buffers Chain

[Paulo Silva]

Hi,
I'm not sure whether I will face problems with other filters modifying
the response body after mine, but for know I'm comfortable as I can
rebuild the full response body just iterating buffers chains.

As I said before I'm using nginx as reverse proxy and my main goal is
to pass the upstream (proxy_pass) response to another local process
(relative to nginx).

I am benchmarking Unix sockets and Shared memory as IPC.
I did it already for Unix Sockets and with my prototype the nginx
"performance" dropped for half the number of requests per second. Of
course I'm doing something really bad.

Is it OK to use socket/connect/send from inside an nginx module?

I would be glad to hear from you.
Thanks,

On Fri, May 23, 2014 at 2:50 PM, Paulo Silva <pauloasilva at gmail.com> wrote:
> Because I don't have deep knowledge of nginx internal and I can not
> find a proper resource about it, the best I can do and with what I am
> comfortable is with body_filter.
>
> Do you think I can notice whether all other 3rd party module filters
> finish modifying the ngx_chain_t *in ?
>
>
>
> On Fri, May 23, 2014 at 2:41 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:
>> Hello!
>>
>> On Fri, May 23, 2014 at 02:17:27PM +0100, Paulo Silva wrote:
>>
>>> Hi,
>>>
>>> On Fri, May 23, 2014 at 12:58 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:
>>> > Hello!
>>> >
>>> > On Fri, May 23, 2014 at 11:57:20AM +0100, Paulo Silva wrote:
>>> >
>>> >> there is other option than modify the auto/modules file?
>>> >>
>>> >> According to my goal (capture the full request response body) I would
>>> >> say that my module must run right before the postpone.
>>> >
>>> > Before the postpone filter you'll get subrequest bodies in your
>>> > filter, which is probably not what you want (the postpone filter
>>> > is to glue subrequest together, correctly ordered).
>>> >
>>> >> Am I supposed to modify the auto/modules like follows?
>>> >>
>>> >> if [ $HTTP_POSTPONE = YES ]; then
>>> >>     HTTP_FILTER_MODULES="$HTTP_FILTER_MODULES $HTTP_POSTPONE_FILTER_MODULE"
>>> >>     HTTP_SRCS="$HTTP_SRCS $HTTP_POSTPONE_FILTER_SRCS"
>>> >> fi
>>> >>
>>> >> # insert my module here!
>>> >>
>>> >> if [ $HTTP_SSI = YES ]; then
>>> >>     have=NGX_HTTP_SSI . auto/have
>>> >>     HTTP_FILTER_MODULES="$HTTP_FILTER_MODULES $HTTP_SSI_FILTER_MODULE"
>>> >>     HTTP_DEPS="$HTTP_DEPS $HTTP_SSI_DEPS"
>>> >>     HTTP_SRCS="$HTTP_SRCS $HTTP_SSI_SRCS"
>>> >> fi
>>> >>
>>> >>
>>> >> I did check my modules config file and I did realize that it is
>>> >> "queued" as HTTP_AUX_FILTER_MODULES. There are different queues for
>>> >> core modules and addons?
>>> >
>>> > The HTTP_AUX_FILTER_MODULES is a generic queue, and it's the
>>> > only one currently officially supported for 3rd party modules.
>>> >
>>> > If you want your filter to be called right before/after postpone
>>> > filter, it should be relatively safe to put it into the
>>> > HTTP_POSTPONE_FILTER_MODULE variable though (and may be with some
>>> > additional checks to make sure the postpone filter is enabled, or
>>> > just a code to enable it unconditionally).
>>> >
>>>
>>> And this is also valid when compiling nginx with the --add-module flag?
>>> How does config file look like?
>>>
>>> My knowledge is restricted to Emiller's Guide To Nginx Module
>>> Development (http://www.evanmiller.org/nginx-modules-guide.html) and a
>>> few debugging hours.
>>
>> Uhm, looking again into auto/modules I think I was wrong, and
>> modifying the HTTP_POSTPONE_FILTER_MODULE variable won't work
>> (added module config scripts are executed later on), you should
>> modify HTTP_FILTER_MODULES variable instead, and put your module
>> into a proper position.
>>
>> Note that the "config" file of a module is just a shell script,
>> and you are free to do more or less anything there.
>>
>> --
>> Maxim Dounin
>> http://nginx.org/
>>
>> _______________________________________________
>> nginx-devel mailing list
>> nginx-devel at nginx.org
>> http://mailman.nginx.org/mailman/listinfo/nginx-devel
>
>
>
> --
> Paulo A. Silva
> http://tech.pauloasilva.com
> http://linkedin.com/in/devpauloasilva/



-- 
Paulo A. Silva
http://tech.pauloasilva.com
http://linkedin.com/in/devpauloasilva/