[development] Refresh rather than re-create D6 cache

[Tomáš Fülöpp (vacilando.org)]

Larry, thanks for the tips; I am looking into how search indexing works and
I definitely will use Views Content Cache (don't know how could I miss it!)




On Mon, Oct 18, 2010 at 15:41, larry at garfieldtech.com <
larry at garfieldtech.com> wrote:

> I... think I follow?  It sounds like you want an approach like the search
> index uses; when you tell it to rebuild the search index it doesn't truncate
> the index but marks all records as "dirty", so they get reindexed over time
> by cron.
>
> You may also find this of use:
>
> http://drupal.org/project/views_content_cache
>
> --Larry Garfield
>
>
> On 10/18/10 8:31 AM, Tomáš Fülöpp (vacilando.org) wrote:
>
>> Yes, Larry, I did experiment with that approach as well. It allows
>> caches to expire at different times, but a) you need to keep some sort
>> of approximate overview about the various expiration delays you're
>> setting (so that they don't have much chance happening at the same time)
>> and b) whenever such cache happens to expire, it still gets deleted at
>> cron and then will have to be re-calculated during the precious time of
>> page request.
>>
>> Currently I am thinking about the following approach - crude pseudo code:
>>
>> // Make sure no other cache has been started over defined period
>> * set buffer period between cache refreshes $cbuffer = 15 seconds
>> * if ( (time()-$lastcacherun) > $cbuffer )
>>
>> // Check if the cache at hand has expired
>> * Set some cache life time $clife
>> * SELECT `created` FROM `cache` where `cid` = 'cachedobjectname'
>> * if ( (time()-$created) > $clife )
>>
>> // Refresh the expired cache
>> * $lastcacherun = time()
>> * recreate cachedobjectname
>> * DELETE FROM `cache` WHERE cid = 'cachedobjectname'
>> * cache cachedobjectname using cache_set  with CACHE_PERMANENT
>>
>> What do you think?
>>
>>
>>
>>
>>
>>
>> On Mon, Oct 18, 2010 at 14:34, larry at garfieldtech.com
>> <mailto:larry at garfieldtech.com> <larry at garfieldtech.com
>>
>> <mailto:larry at garfieldtech.com>> wrote:
>>
>>    Just to make sure, have you tried using the minimum cache lifetime
>>    on the performance page?  It essentially says that a cache record
>>    will always last at least that long, even if a clear is requested
>>    for it. That's your first step if you're finding some caches
>>    clearing too frequently (especially the expensive filter and page
>>    caches).
>>
>>    --Larry Garfield
>>
>>
>>    On 10/18/10 5:22 AM, Tomáš Fülöpp (vacilando.org
>>    <http://vacilando.org>) wrote:
>>
>>        Hi,
>>
>>        In D6, after all caches are cleared, or after a lot of them
>>        expire and
>>        get emptied by cron, the server load spikes seriously because
>>        all such
>>        caches need to be re-populated.
>>
>>        Since this happens more and more on sites I work on, I have been
>>        thinking about using another approach in my modules, in the
>>        sense that
>>        caches would be /refreshed/ rather than cleared and
>>        re-populated. Each
>>        cache refresh would run depending on e.g. a simple variable
>>        storing last
>>        time stamp of any other cache refresh.
>>
>>        This would assure that a) all cached values would be available
>>        at all
>>        times, b) caches would never be re-calculated all at the (near)
>>        same time.
>>
>>        I am about to write logic for this, but wanted to first check with
>>        others in the list -- perhaps some of you know or can point to an
>>        elegant solution that already exists.
>>
>>        Thanks!
>>
>>        vacilando
>>
>>
>>
>>
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