[dev] synchronous write

Manlio Perillo manlio_perillo at libero.it
Mon Oct 22 23:42:07 MSD 2007

Igor Sysoev ha scritto:
> On Mon, Oct 22, 2007 at 01:11:21PM +0200, Manlio Perillo wrote:
>> Igor Sysoev ha scritto:
>>> [...]
>>>>> No, this completely kill the idea of nginx - a worker will be blocked.
>>>> Unfortunately this is required by the WSGI spec, and some "legacy" WSGI 
>>>> applications will block the worker, anyway.
>>>> I have implemented an alternative version that uses a buffer, but I 
>>>> would like to know if using this "hack" is "safe", that is if Nginx will 
>>>> send the correct data to the client and if after setting again the 
>>>> socket to nonblocking mode, Nginx will work as usual.
>>> Yes, it will work. However, you should use the following cycle:
>>>    ngx_blocking(self->r->connection->fd);
>>>    do {
>>>        rc = ngx_http_output_filter(self->r, &out);
>>>    } while (rc == NGX_AGAIN);
>>>    ngx_nonblocking(self->r->connection->fd);
>> That's unexpected, I have assumed that with socket in blocking mode 
>> ngx_http_output_filter never returns NGX_AGAIN.
> No, write() to a socket in blocking mode may send less bytes than you ask.

But NGX_AGAIN is returned also for EINTR?

I have noted that when testing your "patch" over a slow connection 
(qemu) and with a very big buffer, hitting Ctrl-C cause an infinite(?) loop.

P.S.: even with a very big buffer, ngx_http_output_filter never returns

Thanks  Manlio Perillo

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