Module context become NULL on redirect

[Peter Leonov]

Hi Matthieu,

On 09.06.2010, at 20:23, Matthieu Tourne wrote:

> Hi Peter,
> 
> On Wed, Jun 9, 2010 at 2:48 AM, Peter Leonov <pl at programica.ru> wrote:
>> Hello, devels,
>> 
>> got a mysterious crash in a module, that relies on request cleanup hook.
>> In the cleanup handler the module meets its context pointer
>> (via ngx_http_get_module_ctx()) zeroed-out.
>> 
>> The redirected request hits other location and I believe
>> that all contexts have to be dropped. But what could the module do
>> if it has some timers set on the redirected request or if the module needs
>> to free some memory allocated somewhere out of the request pool?
>> 
>> The only way I see is to double store the context in the cleanup hook.
>> Has somebody such a tricky issue solved this way? ;)
> 
> There is an example of a modified internal_redirect function that
> cleans all the contexts, except for the one you want to keep in
> agentzh's chunkin module [1].
> Search for ngx_http_chunkin_internal_redirect() in ngx_http_chunkin_util.c
> 
> [1] http://github.com/agentzh/chunkin-nginx-module

Thank you for pointing this out, filling less lonely now :)

Unfortunately, the module was mentioned does define some nginx variables
and their callbacks may and will be invoked at the rewrite stage with a further
redirecting which the module can not control.

So, according to Maxim Dounin, the only way playing with a cleanup callback
data pointer is the only right way to survive the redirect.

Thanks again,
Peter.