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

[Jacek Medrzycki]

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.

Regards, Jacek