::  Posts  ::  RSS  ::  ◂◂RSS  ::  Contact

Apache doesn't cache htaccess configs

February 5th, 2013
tech  [html]
When I previously suggested that Apache improve performance on .htaccess files by caching them and then watching for changes with inotify, Chris wrote:
just invalidate its cache
This is very sensible, except Apache doesn't actually cache .htaccess files between requests.

Apache checks .htaccess files in a monster function, ap_directory_walk. It's called on every request, and if AllowOverride is set it will call ap_parse_htaccess on every directory from the root out to the leaf. In ap_parse_htaccess you can see that it does have a per-request cache for parsed .htaccess files:

    /* firstly, search cache */
    for (cache = r->htaccess; cache != NULL; cache = cache->next) {
        if (cache->override == override && strcmp(cache->dir, d) == 0) {
            *result = cache->htaccess;
            return OK;
        }
    }

    ... more sanity and safety checks ...

    dc = ap_create_per_dir_config(r->pool);

    ... load and parse the htaccess file into dc ...

    /* cache it */
    new = apr_palloc(r->pool, sizeof(struct htaccess_result));
    new->dir = parms.path;
    new->override = override;
    new->override_opts = override_opts;
    new->htaccess = dc;

    /* add to head of list */
    new->next = r->htaccess;
    r->htaccess = new;

    return OK;

Now it may be that the overhead of parsing .htaccess files just isn't that big and that in many cases a cache would just be a waste of memory. While I doubt that, this is testable. To get a best-case for caching we could test just something like:

   /var/www/foo.html
   /var/www/.htaccess
Comparing this to the version that has the configuration options in a <Directory> block should tell us the maximum we could expect to gain from caching.

Update 2013-02-08: I ran some tests on the above configuration with ab, but the variance was so extreme (some runs of 10k requests averaged 4k/s while others averaged 500/s) that I think something else is wrong. I tried running longer tests with more requests but ab consistently died with apr_socket_recv: Operation timed out (60) before finishing the test.

Comment via: google plus, facebook

Recent posts on blogs I like:

Teacher Housing and the Rot

I recently saw that San Francisco is considering fast-tracking residential development dedicated to teacher housing. There are quibbles between the moderate mayor and the progressives on city council (“Board of Supervisors”) over the exact structure of th…

via Pedestrian Observations June 23, 2019

Instead of “I’m anxious,” try “I feel threatened”

cw: teaching to learn I have a long history with anxiety, and I’m pretty good at noticing when it’s happening. The problem is that I’m always anxious. Noticing anxiety doesn’t snap me out of anxiety– in fact, it often produces meta-anxiety, anxiety about …

via Holly Elmore June 20, 2019

Checkmate on blackmail?

It has been argued that blackmail should be legal if gossip is legal, and even that there are no good consequentialist counterarguments (!). I think this isn’t obvious because the disclosures incentivized by blackmail are systematically worse than gossip.…

via The sideways view June 2, 2019

more     (via openring)

More Posts:


  ::  Posts  ::  RSS  ::  ◂◂RSS  ::  Contact