On Thu, 9 Sep 2010, Ulas Albayrak wrote:

> I'm upgrading from 1.2.21 to 2.0.4, which in other words means I need
> to uninstall the node and delete the old Slony directory before
> installing the new. Setting up a testing environment will be quite a
> big job though, what's the worst thing that can happen if I decide to
> update the live system straight away without testing first? Could it
> interfere with postgresql?

Testing changes and procedures in a test environment is  far safer than 
trying things for the first time in production. We test things to find the 
issues that you aren't able to forsee.

Slony is not the most forgiving piece of software, there are many places 
where user error can leave you with slony cluster that needs to be 
torn-down.  Slony *shouldn't* interfere with postgresql (other than the 
locks slony takes) but I can't promise you it won't.  Slony 1.1.x and 1.2.x 
munge the postgresql catalog to make things work, in theory the uninstall 
will leave your postgresql instances in the proper state but if practice and 
theory always worked out the same then software would never have bugs.

Another option might be to take backups of your databases before you start 
the process so you have something to fall-back to but I've also seen 
instances (not slony related) where the sysadmin/dba thought they were 
taking a backup but didn't test the restore procedure and later discovered 
that the backups they had been taking weren't usable.

I don't know how much time is involved in testing up a test environment, how 
much downtime would cost you or what would be involved in recovering from 
dataloss but testing would lower the risks of issues.

Steve



> On Thu, Sep 9, 2010 at 3:34 PM, Steve Singer <ssinger_pg at sympatico.ca> wrote:
>> On Thu, 9 Sep 2010, Ulas Albayrak wrote:
>>
>>> Hi,
>>>
>>> This might be a quite fundamental question, but the consequences of
>>> being wrong could be dire so I'll ratghr be sure: I need to upgrade
>>> Slony and the guide on the official Slony website says I should
>>> terminate all slon processes then install the newer version of Slony.
>>> My question is can I just build and install the newer version of Slony
>>> parallel to the old and after running the "update functions"-script,
>>> just delete the old slony files?
>>
>> The version you are upgrading from/too controls the answer to this question.
>> Perhaps the docs are less clear then they should be.
>>
>> If you are upgrading from 1.2 to 2.0 you must uninstall slony with
>> "uninstall node" on all nodes using the 1.2.x binaries then install the 2.0
>> binaries and then re-build (init cluster, store node, subscribe set etc...)
>> your cluster.
>>
>> If your going from 2.0.3 to 2.0.4  or 1.2.x to 1.2.21 then you can use the
>> update functions script.  Two versions of slony can't normally be installed
>> at the same time under the same postgresql server directory since the slony
>> install scripts normally put files in $postgresqldir/lib and share that
>> would conflict.
>>
>> In either case you should setup a test system with your old configuration
>> and test your upgrade procedure.
>>
>>
>>
>>>
>>> --
>>> Ulas Albayrak
>>> ulas.albayrak at gmail.com
>>> _______________________________________________
>>> Slony1-general mailing list
>>> Slony1-general at lists.slony.info
>>> http://lists.slony.info/mailman/listinfo/slony1-general
>>>
>>
>>
>
>
>
> -- 
> Ulas Albayrak
> ulas.albayrak at gmail.com
>
>