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https://issues.apache.org/jira/browse/COCOON-2151?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12545682
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Jörg Heinicke commented on COCOON-2151:
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Ellis Pritchard wrote at COCOON-2146:
Thanks for your comment, Ard.
Your analysis may well explain some performance problems we were seeing on our
system; unfortunately I was not around at the time to analyze them, so I can't
really be sure what caused them. The action they took at the time was simply to
cache less, i.e. only the expensive stuff, rather than, well, basically
everything!
Presumably though, if site-usage is fairly uniform, stuff that expires and is
still referenced from AbstractDoubleMapEventRegistry will get regenerated again
at some fairly near point, and replace the old entry with the new one, allowing
it to be freed by the JVM? Only if you're generating lots of unique pages or
short-lived pages and caching them for a long time may it become a 'real'
problem?
I think that ehcache 1.4 (now in beta) may provide at least one solution to
this problem, with its new listeners functionality, which can get notification
of the keys of entries removed (for any reason) from the cache.
However, maybe there's a 'redesign the whole thing' kind of solution too?
As for whether we need it or not: according to "the powers that be" we do need
a persistent cache, so that when we bring the site up under load, on n
instances (each with their own cache), it doesn't hammer our database. The fact
that the site was running without one for 8 months due to this bug is not
enough to convince them otherwise! It's either that, or having to pre-warm the
cache during site-down time (and making site down time longer), or even worse,
running the whole site behind mod_cache with an expiry time of about an hour or
so, to cover any lag in getting it up again. A persistent EventCache just looks
so attractive compared to those options...
> Sub-optimal implementation of AbstractDoubleMapEventRegistry
> ------------------------------------------------------------
>
> Key: COCOON-2151
> URL: https://issues.apache.org/jira/browse/COCOON-2151
> Project: Cocoon
> Issue Type: Improvement
> Components: Blocks: Event Cache
> Affects Versions: 2.1.10, 2.2-dev (Current SVN)
> Reporter: Jörg Heinicke
>
> This is just a follow-up from COCOON-2146 where Ard pointed out some issues
> with AbstractDoubleMapEventRegistry. I just didn't want to lose the
> information when I actually fixed the issue. So I will add it here.
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