Native plugins (was Re: [Nagiosplug-devel] Java Plugins)

[Andreas Ericsson]

Jos Visser wrote:
> With respect to the embedded Perl and embedded Java stuff: Wouldn't is
> be a good idea to extend Nagios with a generic "native plugin" feature
> that would take the form of a shared library conforming to a defined
> interface. Through some extensions to the command language the native
> plugin could be loaded and integrate itself. Then through extension
> keywords we could get the plugin to do stuff (very much like the Apache
> plugin module interface). The entire discussion of embedded Perl,
> embedded Java, embedded Lisp or whatever could then be short circuited
> to native plugin development...
> 

The idea is a bit flawed for a number of reasons.
1. Plugins are highly flexible. They can usually perform many checks 
with a just a little argument tweaking (check_http springs to mind).

2. Plugin development is highly flexible. A plugin can be written in any 
language. A shared library would only get C plugins (and not until 
they're incorporated), so that still leaves a fair number out.

3. Plugins already written in C impose a very minor additional load to 
the system, while retaining the flexibility and "debugability" of a 
separate program (check_http --help springs once again to mind).

4. Internal code to do checks would seriously increase Nagios' code 
volume and make it infinitely less stable.

5. Some plugins needs to use additional environmental variables or run 
as a different user (plugins that need raw sockets, for instance). While 
this can be solved, it requires non-trivial code (temporary privilege 
elevation within the core) and can possibly present a security risk.


> ++Jos.es
> 
> On Fri, Nov 19, 2004 at 09:10:01AM +0100 it came to pass that Andreas Ericsson wrote:
> 
>>Jos Visser wrote:
>>
>>>Plugins in Java are possible, and so is calling Java from Perl. The
>>>performance will probably suck because it takes a long time to
>>>initialize the entire Java runtime environment (JVM, libraries)
>>>
>>
>>Indeed. Java is a hog, which should be loaded once and once only on 
>>every machine where it is to run.
>>
>>
>>>It would probably be better to:
>>>
>>>- Run the check as a daemon and:
>>> - control that daemon from, or
>>> - use the whats-its-name protocol to communicate status directly to
>>>   Nagios
>>>
>>
>>I'd say the best you can do is have a small webapplet running on the 
>>weblogic server which you can fetch some info from and parse in a perl, 
>>C or shell-script. That way you get the info on-demand, but keep from 
>>loading java each time the check is run.
>>
>>
>>>If you are really brave you could extend Nagios with native Java plug-in
>>>support. This would entail linking libjvm.sl into Nagios and hacking
>>>some code to call Java methods directly as check_command's... This would
>>>also mean that you don't need to build up the JVM every time...
>>>
>>
>>I daresay this hack would never make it into the official nagios core 
>>though, especially considering the embedded perl support which nowadays 
>>require completely bewildered solutions to work properly.
>>
>>
>>>++Jos.es
>>>
>>>On Thu, Nov 18, 2004 at 02:28:16PM -0700 it came to pass that David 
>>>Robinson wrote:
>>>
>>>
>>>>I have written Nagios Perl plugins that invoke the weblogic.Admin java 
>>>>class
>>>>to monitor runtime information of my WebLogic Servers.  The weblogic.Admin
>>>>class executes JMX requests to a given WebLogic Server process.  It looks
>>>>like:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>Nagios Process --> Perl Process --> Java Process -->  JMX call across the
>>>>network  --> Remote WebLogic Server Process
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>These plugins do not seem to perform very well.  Does anyone have any
>>>>suggestions on improving the performance of plugins for monitoring 
>>>>WebLogic
>>>>Server?  
>>>>
>>>>
>>>>
>>>>I also tried writing a plugin directly in Java, but I'm not sure if this 
>>>>is
>>>>supported.  Nagios did not receive any output from my Java plugins even
>>>>though I was exiting with the proper error codes.  Has anyone created
>>>>plugins in Java?
>>>>
>>>>
>>>>
>>>>Thanks for your assistance,
>>>>
>>>>Dave
>>>>
>>>
>>>
>>-- 
>>Andreas Ericsson                   andreas.ericsson at op5.se
>>OP5 AB                             www.op5.se
>>Lead Developer
>>
>>
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> 
> 

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Lead Developer