NGINX error log format documentation

Jan Teske jan.teske at
Sun May 26 21:19:11 UTC 2013

That was helpful. Thank you!

On May 23, 2013, at 21:31 , Francis Daly <francis at> wrote:

> On Thu, May 23, 2013 at 08:47:42PM +0200, Jan Teske wrote:
> Hi there,
>> I want to parse NGINX error logs. However, I did not find any 
>> documentation concerning the used log format.
>  less src/core/ngx_log.c
> should probably show most of what you need. Combine that with
>  grep -r -A 2 ngx_log_error src
> and looking at an error log and you should see that it is "a small number
> (five, I think) of fixed fields, followed by free-form text".
>> While the meaning of some 
>> fields like the data is pretty obvious, for some it is not at all. In 
>> addition, I cannot be sure that my parser is complete if I do not have a 
>> documentation of all the possible fields. Since it seems you can change 
>> the access log format, but not that of the error log, I really have no 
>> idea how to get the information I need.
> I (strongly) suspect that the error log line format details is not
> something that nginx wants to commit to holding stable.
> If you want to do any more parsing than "free-form text after a handful of
> common fields", then you'll probably want to care about the version you
> are using. Or at least, flag an imperfectly-recognised line if anything
> doesn't match what you expect.
>> Is there such documentation?
> It's hard to beat the contents of src/ for accuracy.
> Choose the "identifying" string in the line you care about, find the
> matching ngx_error_log call, and then see what free-form text it provides
> in the current version.
> 	f
> -- 
> Francis Daly        francis at
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