[Spacewalk-list] How to update running applications?

Michael DeHaan mdehaan at redhat.com
Tue Oct 7 16:27:26 UTC 2008


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.
>>
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>>     
>
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