[dev] synchronous write

Manlio Perillo manlio_perillo at libero.it
Wed Oct 17 00:16:56 MSD 2007

Igor Sysoev ha scritto:
> [...]
>>>> My problem is how to handle NGX_AGAIN in the write callable, since I 
>>>> can't return control to Nginx (and setting the event handlers).
>>>> As an example (pseudo code):
>>>>  while ((rc = ngx_http_output_filter(r, &out) == NGX_AGAIN) {
>>>>      sleep(...)
>>>> But this does not works.
>>> This code should be as:
>>> my_handler(ngx_event_t *wev)
>>> {
>>>    ...
>>>    rc = ngx_http_output_filter(...);
>>>    if (rc == NGX_AGAIN) {
>>>        r->write_handler = my_handler;
>>>        ngx_handle_write_event(wev)
>>>        add_timer(wev, XXX)
>>>        return;
>>>    }
>> But if control does not return to Nginx, how can my handler be called?
> "return" should return control to nginx.

The problem is that "return" returns control to the WSGI application and 
not to Nginx.

In the current implementation of mod_wsgi I'm raising an exception when 
Nginx returns a NGX_AGAIN.

A solution for this problem is to buffer all the data that the WSGI 
application want to send using the write callable, but I would like to 
know if there are other solutions, since buffering in this way is not 
allowed by the WSGI spec.

Thanks  Manlio Perillo

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