On Fri, 8 Feb 2013, Joe Orton wrote:
On Sun, Feb 03, 2013 at 08:32:11PM +0100, Niklas Edmundsson wrote:
Hi all!
Something is definitely fishy with mod_socache_shmcb as shipped with
httpd 2.4.3. I'm hacking on a module that uses 16byte indexes
(IP(v6) addresses) to store 2byte counters (16bit uint), these sizes
are given as hints in the call to the init function.
After an hour or so with production load, which means
retrieve/store/remove for each connection, it consistently crashes
in mod_socache_shmcb.c
Hi Niklas, thanks for the report and the analysis. You are passing
specifically avg_obj_size = 2, avg_id_len = 16 in the hints?
Yup, that's the intention at least. The actual hint-struct is declared
as:
static struct ap_socache_hints iplimit_cache_hints = {
16, /* average length of IDs */
sizeof(apr_uint16_t), /* avg size of objects */
300000000 /* interval between expiry runs */
};
It looks like something goes wrong with the sizing heuristics with small
obj/id sizes. I can't work out exactly why but it's definitely a bug.
I'm hoping for someone familiar with that code to chime in with ideas,
as the fix for this isn't really obvious to me either...
/Nikke
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Niklas Edmundsson, Admin @ {acc,hpc2n}.umu.se | [email protected]
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Frood: really amazingly together guy
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