Can not use $bytes_sent in module (complex values)

Benjamin Grössing mailtogroe at
Wed Sep 19 21:11:57 UTC 2012

Hi Vladimir, hi Maxim!

Thanks for your answers. I've had a look at the rewrite module -
unfortunately it does not support the $bytes_sent variable either as
configuring "if ($bytes_sent) { }" throws the error: [emerg] unknown
"bytes_sent" variable.

Nice to hear that there is a plan to include all variables in the
complex value system - I think that would make that part a of nginx a
lot more clear! I'd be happy if I could contribute here, but I am not
sure about the details. Is there any guide to contributing to nginx
available or do I just have to create a patch file and post it here?
Can I just start with the nginx 1.2.3 source code from


2012/9/19 Maxim Dounin <mdounin at>:
> Hello!
> On Tue, Sep 18, 2012 at 03:55:38PM +0200, Benjamin Grössing wrote:
>> Hello,
>> I am currently working on a nginx module, that parses user defined
>> strings for variables using ngx_http_complex_value_t. That works great
>> with all variables defined in ngx_http_variables.c (i.e.
>> $body_bytes_sent). However, variables as $bytes_sent do not exist here
>> since ngx_http_log_module uses its own variable parsing system. What
>> is the best way to use these extra variables in my module? I have
>> thought of the following options, I am not very sure about what is the
>> best way to go:
>> a) Copy the ngx_http_log_module code in my own module and rename every
>> single type and function to avoid double definitions. Reuse functions
>> and types from there.
>> b) Move the ngx_http_log_module code in my own module directory and
>> compile it only there. Reuse functions and types from there.
>> c) Write own variable parsing system, reuse a few snippets from
>> ngx_http_variables and ngx_http_log_module, whatever fits best.
>> d) Use complex values and try to extend the ngx_http_core_variables
>> array to include $body_bytes_sent and the other missing variables (I
>> don't understand why they are not included here anyway?).
>> e) Any better way to achieve that?
>> I'd really appreciate your help.
> All variables that are currently present only in log module should
> really be made available as normal variables as well.  They aren't
> yet mostly due to historical reasons (log module appeared before
> normal variables were implemented) and the fact that most of
> them are only usable for logging.
> No idea what would be best for your particular module, but in
> general it's better to use complex values and what's available via
> normal variables.  Unless you need $bytes_sent right now - it's
> probably the best aproach, and missing variables will be available
> once they appear in nginx.
> (The latter is something you may speedup by submitting a good
> patch.  Most tricky part here would be to follow coding style.)
> Maxim Dounin
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