On 10/30/2009 08:37 AM, Octavian Râşniţă wrote:
You are probably right. I don't think I understand very well why the
form should be cloned,
Carl is right on the money :-) Cloning is definitely necessary and is
what I use in my single-process cache. Think of the case where two
different clients try to process the same form at roughly the same time
(and are using the same catalyst process)
1. A requests a page gets the form first and initialises the cache
2. B requests the same page gets the same form object from the cache
3. A submits the form with errors using the same form object as B
(from the cache)
4. B submits the form without errors but using the same form object
as A (from the cache)
Not too sure, but either A gets no errors or B gets the errors from A.
There are a bunch of other similar cases, but the upshot is that we have
to separate the objects used by different requests.
The fix is to simply store a clone in the cache, and when you retrieve a
cached object you make another clone. This is what I did, and despite
the double clone operation, we still get a noticeable improvement.
Perhaps doing a clear_errors() on the form before retrieving would be
faster, but I'm not sure this would disentangled the requests sufficiently.
but maybe we could choose which of the forms need
to be cached, and we could choose to cache only those forms that
couldn't be modified, so they shouldn't be cloned.
This way the caching of entire forms could be done probably easier at
least for those cases of forms that don't need to be cloned.
I'm not too sure, but caching forms that include callbacks is probably
not possible. Caching forms that get their options from a model may not
give you a significant speed up. Pre-caching all cachable forms at
start-up is probably possible.
Unfortunately this is a very big issue because the speed decrease is
very high and if a page uses a form made with HTML::FormFu it becomes
unimportant if other parts of the page do caching, or if we use database
query improvements.
This is a huge issue for me as well. I have a deployment due in early
December and I need to get this working under mod_perl by then. The
fact that the single-proccess cache produces a noticeable improvement
(2-3 times faster using the Catalyst test server) is promising. The
effect of the single-process cache on a mod_perl environment is much
less: you have more processes and apache recycles your processes after a
certain number of request, so the cache hit rate is much smaller.
Anyway, I have an unrelated deadline on Wednesday, after which I'll have
more time to work on this, perhaps with some help from the list :-)
Ciao!
Kal
PS I need a holiday.
--
Kahlil (Kal) Hodgson GPG: C37B01F4
Head of Technology (m) +61 (0) 4 2573 0382
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the parts you are reassembling were disassembled by you. Therefore,
if you can't get them together again, there must be a reason. By all
means, do not use a hammer." -- IBM maintenance manual, 1925
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