[Nagios-users] Nagios 2.0 Event Broker and DB Support

[garrick]

Once the modules have access to nagios internals, let's do more than
just receive events.  I'd like to dynamically define services and remove
them a few hours later.  I'd like to override the contacts.cfg files and
substitute user information with an RBAC from LDAP (along with the CGI's
authn pieces).  I can probably think of a few more subsystems I could
override to better integrate into my environment.

About the dynamic services thing... I manage a research computing
cluster and each job tends to be a bit fragile.  During the lifetime of
a job, there are several scriptable checks I can do to check the health
of the job and the nodes it is using.  It would be fun if each job could
temporarily be its own service.  While a job is running, nagios would
monitor it just like any other service.  I know the current solution is
to use a single generic job service with passive checks submitted by
an external process that would identify any particular problems.



On Fri, Aug 01, 2003 at 12:02:03AM -0500, Ethan Galstad alleged:
> Sorry for the crosspost, but the nagios-devel list is usually pretty 
> quiet when I request comments about new features I'm implementing.  
> This one is bigger than most, so I wanted to reach more people.  This 
> is a bit long, so bear with me...
> 
> I am almost complete with coding for 2.0.  Two big things remain: the 
> event broker and DB support (which is currently broken).
> 
> My original intent was to develop the event broker as a separate 
> application, tying it to Nagios with a unix domain socket.  Nagios 
> would send the event broker information about the everything that was 
> going on (service checks, downtime, flapping, log entries, etc.).  
> The event broker would be able to load user-developed modules (object 
> files) at runtime and pass various types of Nagios data to them for 
> processing.  This is all fine and good.  I have a working prototype 
> of the event broker that does just this and seems to work okay.  I 
> got to thinking that it was rather stupid to develop a separate 
> application for this when I could simply have Nagios load user-
> developed modules itself.  Doing this would give the modules the 
> benefit of having access to internal Nagios structures and functions 
> (which is good and bad - see below).
> 
> Here's an overview of how it would work:
> 
> - Nagios would load user-specified modules (object files) at startup 
> using the dlopen() function.
> 
> - Nagios would call the module's initialization function (the name of 
> which would be standardized).
> 
> - The module's init function would register for various types of 
> Nagios event data (service checks, host checks, log entries, event 
> handlers, etc.) using callback functions.
> 
> - When Nagios encounters an event for which a module has registered a 
> callback function, Nagios would call that module's function and pass 
> it data relevant to the event.  The module is then free to do 
> whatever it wants to that event data.  An example might be to log 
> service checks, performance data and log entries to MySQL, etc.
> 
> - Before shutting down, Nagios calls the module's de-init function.  
> This allows the module to clean up any resources it may be using.
> 
> 
> Seems good in theory.  Heck, might even work okay.  However, there's 
> a big problem I have with it.  If I implement things this way, the 
> user-developed modules would have access to internal Nagios data 
> structures and functions.  This is not necessarily bad, as ill-
> behaved modules would not be adopted by too many people. :-)  
> However, modules that might be compiled and working fine
> for Nagios 2.0 might segfault under future versions if the internal 
> data structures change.  Here's an example of what I mean:
> 
> User module registers for Nagios service check data using its 
> mymod_handle_servicecheck() function, which has a prototype of:
> 
> 	int mymod_handle_servicecheck(service *);
> 
> 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'm afraid I'm a bit over my head on how to handle this one.  Some of 
> you developers out there must have experience with this type of 
> thing.  If so, how did you handle it?  What would you recommend?  
> Comments, suggestions, flames?  Is there a better way to accomplish 
> this?  Speak up now.
> 
> What does this have to do with DB support, you ask?  Well, if I 
> implement the event broker as I have proposed I will be yanking 
> native DB support out of Nagios completely.  You can then write a 
> module to log to a DB if you want. :-)
> 
> PS: I had originally planned on exposing almost all of Nagios' data 
> and events to the broker, but I may have to scale that down if I plan 
> on getting 2.0 out this century.  Perhaps just support for:
> 
> 	- Service and host checks
> 	- Event handlers
> 	- Log data
> 
> This would allow the development of modules to log check information, 
> performance data, and log file data to a DB (or whatever).
> 
> 
> Ethan Galstad,
> Nagios Developer
> ---
> Email: nagios at nagios.org
> Website: http://www.nagios.org
> 
> 
> 
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