Nagios 2.0 Event Broker and DB Support

[Ethan Galstad]

On 4 Aug 2003 at 11:37, David Parrish wrote:

> > The service struct is an internal Nagios structure definition which 
> > changes between Nagios versions.  If the user module is compiled for 
> > use with Nagios 2.0 and it's definition of the service struct, it 
> > will have problems if it is not recompiled for future versions of 
> > Nagios.
> > 
> > Off the top of my head, I could overcome this by requiring that the 
> > user modules indicate (by calling a function) what version of Nagios 
> > they are compiled for.  If they report anything but the current 
> > version (or do not report at all), unload them so they can do no 
> > harm.
> 
> I like the idea a lot, and I can see heaps of potential for some funky
> dynamic monitoring stuff..
> 
> In the .h file which modules will #include, add this macro:
> 
> #define NAGIOS_API_VERSION(x) int __nagios_api_version = x;
> 
> 
> Each module must insert (near the top) a nice simple line like:
> NAGIOS_API_VERSION(3)
> 
> 
> Then, when you dlopen() the module, use something like:
> 
> #define REQUIRED_API_VERSION 3
> if (*((int *)dlsym(dlhandle, "__nagios_api_version")) != REQUIRED_API_VERSION)
> {
> 	printf("Wrong module version... not loading\n");
> 	return;
> }
> 
> to get the version number before you call the init function. If the version
> number is not exactly right, don't load the module. I think that will
> work...
> 
> It might be nice in principal to allow multiple versions or some kind of
> backward compatibility, but I doubt it's worth it, for the stability you
> could potentially lose.
> 
> Just make sure that you increase the api version in the core code whenever
> you change it, and it'll be sweet.
> 
> 
> Also, on second thought, it might be worthwhile putting in some compiler
> checking #ifdef blocks, so that an old version of a module won't compile
> with the new headers..
> 

Thanks David - this is exactly what I was looking for. :-)

Ethan Galstad,
Nagios Developer
---
Email: nagios at nagios.org
Website: http://www.nagios.org



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