[Spacewalk-list] How to update running applications?

[Adrián Márques]

Many thanks Gerhardus for your kind and helpful answer.

Yesterday, through JBoss, I found out that the functionality I'm looking 
for has been branded with the terms 'hot deploy' or 'hot patching', 
which finally turned up some more interesting search results that 
clearly state that this is far from the trivial matter I first thought 
it'd be.

I realise that the first half of my previous mail may be off-topic, I 
apologize for that, but the second part still stands. Particularly I'd 
still like to know if the spacewalk client can be configured to just 
download the rpms and only install them when told to do so from the 
command line.

Thank you all guys for your attention.

Regards.

Adrián.

Gerhardus.Geldenhuis at gta-travel.com escribió:
> 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
>
>   
>> -----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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