Re: Detecting running application

[Richard Frith-Macdonald]

On 11 May 2006, at 14:24, Chris B. Vetter wrote:

> On 5/11/06, Richard Frith-Macdonald <richard@tiptree.demon.co.uk>  
> wrote:
> [...]
> > > I've just tried to use DO, but apparently this will introduce a  
> > racing
> > > condition if two applications are started within just a few  
> > seconds,
> > > eg. during log in.
> > Not sure what you mean ... one (and only one) of the applications
> > should be able to register with a particular name.  If that's not the
> > case, then DO name serving is thoroughly broken ... so I suspect any
> > problem is with the logic in your code.  If not, there is a bug we
> > need to fix in the nameserver code.
>
> I was experimenting by simply sending notifications back and forth
> between bundle A and bundle B. That would introduce a racing
> condition, as sending a message from A back to B might be delayed, so
> B would finish the initialization even though A was already loaded.

Oh sure ... I thought you meant using the DO name service code (as  
you mentioned using gdomap earlier) not just sending messages around.

> Next, as suggested, I tried to use NSMessagePorts and
> NSPortNameServer. However, -registerPort:forName: seems to completely
> ignore the given name, instead looks like it always uses the
> application's name to register the port.

Absolutely not ... but I looked at the code for the  
NSMessagePortNamesSrver and noticed that it has a bug in handling the  
names ... it needs to ensure that any name it is given is a valid  
filename (not a path), but it isn't doing that.  I'll write a fix to  
mangel paths into filenames.
In the meantime you could, as a proof of concept, use the last path  
component of the bundle path rather than the full thing.

> As an example, imagine a bundle that would scan a folder for
> images/pictures and display each as your desktop background
> successively.
>
> Now it wouldn't make sense to load such a bundle more than once,  
> would it?
> Probably, you would have it loaded with the first application you  
> start.

Actually I would have thought it made sense to have it be an app/ 
daemon rather than a loadable bundle.

> > I think I'm clear now that you only want one application to be able
> > to load bundles , but is that one application per user, one per host,
> > one per lan?
>
> Per user, see above.

> > Why is it important that only one application is able to load these
> > bundles?
> [...]
>
> It's just one bundle and see above. Multiple instances just wouldn't
> make sense in this example, plus they would consume a lot of memory
> and generally bog down your box.

Well, I *sort* of see ... but it looks to me like the sort of  
functionality you are describing would make more sense as apps or  
daemons or as functionality provided as services than in bundles.   
What about a simple background app built solely to run the  
bundles ... then you never need to worry about the bundles being  
loaded in multiple apps since there is only a single app loading them  
all.