sending data in "chunks"

Manlio Perillo manlio_perillo at
Sat Sep 22 00:02:39 MSD 2007

Igor Sysoev ha scritto:
> [...]
>> So, please let me know if I'm right:
>> - when a call to ngx_http_output_filter with a buffer chain of *only
>>   one* buffer returns with NGX_OK, it means that the *entire* buffer
>>   has been sent to the client.
> Yes. Or if gzipping is enabled the entire buffer is buffered inside zlib.
>>   If nginx return NGX_AGAIN then I have to set the
>>   request->write_event_handler so that my handler is executed when the
>>   socket is ready to send data again.
> Yes.

I have done some tests with mod_wsgi.

If a WSGI application returns a big buffer, ngx_http_output_filter 
returns NGX_AGAIN, *however* the entire buffer is sent to the client.

This is the same behaviour with a "full" buffer chain, with the 
difference that even if I return NGX_AGAIN from my request handler, the 
client reads the full response (with a "full" buffer chain in a previous 
test, I have to return NGX_OK, when receiving NGX_AGAIN).

So, it seems that nginx will send the entire content of a buffer, as 
soon as control returns to it.

This is important for me: when ngx_http_output_filter returns NGX_AGAIN, 
should I have to send again the previous buffer when my handler is 
called from the write event, or I can safely send the next buffer?

Thanks and regards  Manlio Perillo

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