[Zope-dev] RAM Cache Manager "next_cleanup" not working?

[Júlio Dinis Silva]

>"Júlio Dinis Silva" wrote:
> > Looking into 
>lib.python.Products.standardCacheManagers.RAMCacheManager.py
> >
> > I found something it looks like a problem in the code and
> > I came to a solution which solves the problem in subject althougt
> > I dont know If this is a safe solution, It works for me.
>
>The theory behind the current solution is that a cache cleanup operation
>occurs:
>
>- only if a certain amount of time has passed since the last cleanup,
>and
>
>- only when adding a new entry to the cache.
>
>Then, even during a cleanup, nothing is removed if the number of entries
>is below the threshold.
>
>The idea is that cache hits should be as fast as possible.  Cleanup
>occurs on cache misses instead.  The only side effect is that watching
>for entries to get cleaned up on the stats page won't act as you might
>expect.  The number of entries will *always* go above the threshold.
>The entries will be cleaned up next time there's a cache *miss*.
>
>This is *not* a bug.  But maybe we could "fix" it by executing a cleanup
>every time users look at the stats page. :-)
>
>Another idea is for you to create your own cache manager.  In fact we
>(Digital Creations) encourage the creation of alternate cache managers.


Hi Shane,

Thanx for your reply.
I understand the theory you explained to me. But even that
theory being correct and now I know better how
the RAM Cache Manager works, and even thinking of doing another
cache manager, another point of my post is that something is
not working:

I'm testing this, caching a page that only creates one entry in
the cache, because there is nothing different with that page to
create multiple cache entries (Query_string vars, or other stuff), i.e, the 
"cache keys" of this page is always the same it doesnt receive any 
parameters to create a different entry. And taking this in
mind even with a threshold of 0 (zero) the next_cleanup value is never
tested in the code. So this is what I think is somehow wrong with the
code:

>The theory behind the current solution is that a cache cleanup operation
>occurs:
>
>- only if a certain amount of time has passed since the last cleanup,
>and
>
>- only when adding a new entry to the cache.

Soo what I was not able to reproduce with the current RAM Cache Manager code 
is the "certain amount of time has passed" condition.
Because of that there was my solution of returning "default" in
the ZCache_get code which I agree with you it slows cache hits, but
was the only way I got to put the interval_period to work.

If you could be so kind and do a little test:

-create a dtml method with only this line of code: <dtml-var ZopeTime>
-create a Ram cache manager, define 0 (zero) for the threshold and
5 seconds for the cleanup interval, and associate your dtml method
with this Ram Cache manager.
-Then go to a browser and request several times the dtml method
and you will see that the zopetime returned by the dtml method
never changes, even after 5 seconds.

Isnt this suppose to work? I mean, there is a threshold of 0 (zero)
so when the 5 seconds pass the call to cleanup should cleanup
this entry because there will be 1 entry and the threshold is 0 (zero).

Thanx again for your reply,
Best Regards,
Julio Dinis Silva


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