[Spacewalk-list] How to update running applications?

[Adrián Márques]

Thanks a lot Michael.
I'd never heard of condrestart before and your other suggestions also 
seem to be more than worth checking out.

If I understood you correctly though, the advice you are giving me is 
geared towards updating services and in the process 
starting/stopping/restarting them based on conditions (I'll be looking 
into the links you provided to verify whether this is right). The 
conundrum I'm facing is that this is a desktop app, picture ooffice as 
an example, and I can't restart it while the users are logged in it.

The hosts were this app will be running will be dedicated, so I'm 
leaning towards the idea of hacking the spacewalk client as I mentioned 
before (so it won't install the updates until told to) and periodically 
install downloaded rpms either at boot time or whenever I can ensure 
that no users are logged into this app. Do you consider this a terrible 
solution? Am I trying to defeat RPM with this? Is there a better 
alternative?

Thanks.

Adrián.

Michael DeHaan escribió:
> Gerhardus.Geldenhuis at gta-travel.com wrote:
>> Hi Adrián,
>> The question is probably more suitable on a rpm list.
>> We don't distribute our jar's with rpm but I appreciate your dillema.
>>
>> I don't personnally think that for such complex applications, rpm is 
>> the right way to upgrade with. I see rpm has a way to distribute 
>> "core" stuff, and not suitable for distributing weird and wonderfull 
>> applications that requires restarts and database upgrades etc. There 
>> is application servers and frameworks that is better suited for this 
>> type of thing and that sits on a logically higher level. JBoss, 
>> Wesphere and I think even tomcat has some basic stuff build in.
>>
>> Regards
>>
>>   
>
> This is generally true only for applications that are packaged 
> /poorly/.   Properly packaged RPMs can be configured to do 
> "condrestart" as needed.
>
> If you need something more advanced, this is typically where you would 
> want to look at something like puppet/cfengine/bcfg2 where you can 
> describe the state you want your services to be (and remain) in.
>
> Also you may be interested in a simple tool such as Func 
> (http://fedorahosted.org/func) for restarting services remotely.   It 
> is in many ways easier to deploy than SSH and also provides you a way 
> of defining arbitrary groups of systems to send commands to.
>
> --Michael
>>> -----Original Message-----
>>> From: spacewalk-list-bounces at redhat.com 
>>> [mailto:spacewalk-list-bounces at redhat.com] On Behalf Of Adrián Márques
>>> Sent: 06 October 2008 18:45
>>> To: spacewalk-list at redhat.com
>>> Subject: [Spacewalk-list] How to update running applications?
>>>
>>> Dear all,
>>>
>>> I'm having a difficult time in finding the correct forum to pose 
>>> this question since I guess it's part spacewalk, part RPM, part 
>>> basic aplication design.
>>>
>>> Being an RPM end-user for years I had always assumed that updating 
>>> running apps was a piece of cake with RPM. After all, I always did 
>>> it and the most I got were occasional messages such as "Firefox 
>>> restart required", never encountering other side-effects.
>>>
>>> However, after reading through the RPM guide, getting my hands dirty 
>>> trying to package an app, scouring the internet for info and asking 
>>> around in the RPM mailing list, I'm still not sure how to write my 
>>> RPM so updating won't be an issue.
>>>
>>> The scenario is the following: I'd like to use spacewalk to 
>>> distribute a custom desktop app. Hence, it's unavoidable that some 
>>> users will be working at the time of an update. So far I've 
>>> identified two problems with this, 1) If I have to modify the app's 
>>> database schema as part of the update, the running app might break 
>>> down if it's not aware of the change 2) This happens to be a java 
>>> app, so in case a jar gets updated a class might get loaded that is 
>>> not compatible with those already loaded by the running app.
>>>
>>> I understand that what I've explained so far might be outside of the 
>>> scope of the subjects treated in this mailing list, if so, please 
>>> just treat it as a detailed background problem description.
>>>
>>> What I would like to know from you guys is whether you've had any 
>>> problems when updating apps through Satellite/Spacewalk due to them 
>>> being running at the time or what precautions (if any) you take when 
>>> doing so.
>>>
>>> Finally, I suppose that as a last resort I could hack the spacewalk 
>>> client to only download updates and not install them until it is 
>>> told to do so from the command line. Is this already possible? If 
>>> not, where's the place to start with hacking this?
>>>
>>> I thank you all for your time and attention. It'd be amazing if you 
>>> had any comments regarding my background issue, but I'll be more 
>>> than satisfied and grateful if you could just provide any feedback 
>>> on those questions strictly spacewalk-related.
>>>
>>> Thanks.
>>>
>>> Adrián.
>>>
>