[Erp5-dev] Memcached usage in selection tool

[Yoshinori Okuji]

On Thursday 28 August 2008 10:06:56 Łukasz Nowak wrote:
> Hello,
>
> In selection tool (portal_selections/manage_configure) it is possible to
> use Persistent Mapping or Memcached Tool.
>
> I'd like to know what is the status and advantages of using Memcached
> Tool instead of Persistent Mapping. Would be memcached faster on busy
> site? It will be faster/more scalable, isn't it?

As far as I see, the speed is not that different. But it makes a lot of 
difference in data size, since memcached does not store old data. Also, even 
though Selection supports a conflict resolution, memcached is usually faster 
when conflicts in selection objects happen frequently, because memcached does 
not recognize transactions, and a conflict resolution requires more 
interactions with a storage.

> I've been using it for some time, and while most things works, setting
> relation by 'Set Relation' does not works (rev 23134). Correct me if I'm
> wrong, but Memcached is not used in test runs for
> ERP5Form/tests/testSelectionTool.py?

It should be tested there. I don't remember why any test was not written for 
that, though.

> So - should be memcached in selection tool used on production
> environment? What is its status? Alpha, beta,
> ready-for-community-testing?

In reality, it is pretty stable, and used in production. Note that, however, 
it slightly changes the user-visible behaviors, because selections would be 
lost when restarting memcached. If you don't like this, it is necessary to 
use either ZODB or a memcached-compatible persistent storage (which is more 
or less slower than memcached).

YO
-- 
Yoshinori Okuji, Nexedi KK President / Nexedi SA CTO
Nexedi: Consulting and Development of Free / Open Source Software
http://www.nexedi.co.jp/
ERP5: Full Featured High End Open Source ERP
http://www.erp5.com/
ERP5 Wiki: Developer Zone for ERP5 Community
http://www.erp5.org/