[Erp5-dev] Cloning ERP5 instance - problem with connection strings

[Łukasz K. Nowak]

Hello,

Dnia 02-06-2007, sob o godzinie 12:14 +0200, Jacek Medrzycki napisał(a):
> Hi.
> 
> We sometimes fell a need to clone current state of our client's 
> production ERP5 instance, for example to check client's complaint 
> without writing to production database.
> 
> Cloning the Zope database seems to be easy - just copy data.fs to new 
> location, there are even backup tools that do it on the fly without 
> stopping zope. However, there is a problem. Sql connection strings are 
> stored in ZODB, thus after starting a clone it tries to write to the 
> production sql database! If there are unfinished activities or so, the 
> state of production sql database could be modified before we change ERP5 
> connection strings. Then, mysql database would be inconsistent with 
> production ZODB! And reindexing is not the solution in production 
> environment, as it takes time and before finishing the ERP5 site is 
> partially unusable.
> 
> Our solution is to:
> - stop production
> - clone production ZODB and production SQL (with mysqldump), save 
> mysqldump results for restoring production
> - start clone and modify it's connection strings
> - restore production SQL from mysqdump (it can takes a while, but is 
> much more faster then reindexing).
> - start production.
> 
> But perhaps there is a better solution? For instance, is it possible to 
> start ERP5 in a way that it would not be writing to SQL database, 
> allowing to safely change connection strings? I was thinking about 
> disabling timer service in zope.conf for a while, but I'm not sure if it 
> is enough to be sure that there would be no SQL writes.

We are using virtualization to workaround such problem. But when your
sql connection string contains hostname it is still dangerous.

Because you want to "block" any attempt of connection to original mysql,
you might think about:
 - blocking port on firewall
 - use selinux to temporarily block clone's connection to original mysql
socket/ip

After reconfiguration you may remove above locks.

Bye,
Luke  

-- 
Łukasz Nowak R&D Ventis http://www.ventis.com.pl/
tel: +48 32 768 16 85 fax: +48 32 392 10 61
``Use the Source, Luke...''