[Spacewalk-list] How to update running applications?

[Adrián Márques]

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.