questions about http variables: flags and no_cacheable
mdounin at mdounin.ru
Fri Apr 16 03:16:35 MSD 2010
On Thu, Apr 15, 2010 at 10:41:37PM +0200, Manlio Perillo wrote:
> In my ngx_http_gateway module
> I'm implementing support for script_name and path_info variables, and I
> would like to ask some questions.
> * some variables have the ``NGX_HTTP_VAR_NOCACHEABLE`` flag set, however
> the get_handler set ``v->no_cacheable = 0``.
> What is the effect of setting ``v->no_cacheable = 0`` ?
There is no effect, it will be set to 1 anyway once flag is here.
Though this way it's consistent with cacheable variables and
NGX_HTTP_VAR_NOCACHEABLE flag can be removed safely (and
no_cacheable will be still initialized).
Note well that right now it's actually not needed at all as
indexed variables are allocated using ngx_pcalloc() (and
non-indexed variables don't use no_cacheable). But there was a
timeframe when it was indeed required.
> * what is the purpose of the NGX_HTTP_VAR_NOHASH flag?
These variables can only be used via index, not by name. It's
small optimization which may be used when you know that variable
isn't needed in ssi and/or perl.
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