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From Parin Shah <>
Subject Re: mod-cache-requestor plan
Date Wed, 20 Jul 2005 06:33:36 GMT
Hi All,

We are now almost at consesus about this new mod-cache-requester
module's mechanism. and now I believe its good time to start
implementing the module.

But before I could do that, I need some help from you guys.

- I am now comfortable with mod-cache, mod-mem-cache, cache_storage.c,
cache_util.c etc.

- But still not too sure how to implement couple of things.

1. How to start the new thread/process for mod-cache-requester when
server start. any similar piece of code would help me a lot.

2. how mod-cache-requester can generate the sub request just to reload
the content in the cache.

3. In current scheme, whenever mod-cache-requester pulls first entry
from pqueue ('refresh' queue) it re-requests it to reload. now by the
time this re-request is done, page might actually have been expired
and removed from cache. in such case should mod-cache reload it or
should wait for next legitimate request.

Your thoughts on any/all on these issues would be really helpful.


On 7/19/05, Ian Holsman <> wrote:
> Parin Shah wrote:
> >>you should be using a mix of
> >>
> >># requests
> >>last access time
> >>cost of reproducing the request.
> >>
> >
> >
> > Just to double check, we would insert entry into the 'refresh queue'
> > only if the page is requested and the page is soon-to-be-expired. once
> > it is in the queue we would use above parameters to calculate the
> > priority. Is this correct? or let me know If I have mistaken it.
> >
> yep.
> thats the idea.
> refresh the most-popular pages first.
> >
> >>see memcache_gdsf_algorithm() in mod_mem_cache.c for an implementation
> >>of this, which assumes 'length' of request is related to the cost of
> >>reproducing the request.
> >>
> >>the priority queue implementation is sitting in mod_mem_cache, and could
> >>be used to implement the 'refresh' queue I would think.
> >>
> >
> > I feel comfortable with mod-cache and mod-mem-cache code now. but we
> > also need to start new thread/process for mod-cache-requester when
> > server starts. I am not too sure how we could implement it. any
> > pointers to the similar piece of code would be really helpful to me.
> >
> I don't have any code which does this to share with you (others might
> know of some).
> > Thanks,
> > Parin.
> >
> --Ian

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