[et-mgmt-tools] Introducing cobbler triggers (coming in 0.4.7)

[Michael DeHaan]

This feature is to be included in the yet-to-be-released 0.4.7 ...

Suppose you are working with a 3rd party system of some kind and want to 
interact with it when cobbler commands are run.   
Examples potentially include doing some custom logging, or perhaps 
interacting with some remote resource (power management?  networking 
hardware? who knows?).

Triggers provide a way to do this.

Cobbler 0.4.7 will include the following trigger directories:

/var/lib/cobbler/triggers/add/profile
/var/lib/cobbler/triggers/add/system
/var/lib/cobbler/triggers/add/distro
/var/lib/cobbler/triggers/add/repo
/var/lib/cobbler/triggers/delete/profile
/var/lib/cobbler/triggers/delete/system
/var/lib/cobbler/triggers/delete/distro
/var/lib/cobbler/triggers/delete/repo


When an object is added or deleted through the cobbler command line (or 
the API), all trigger scripts in these directories will be executed.   
The parameter to the script will be the name of the object
being added or deleted.   If you have a trigger for "delete/system", and 
run "cobbler system delete --name=AA:BB:CC:DD:EE:FF", the script's 
parameter will be "AA:BB:CC:DD:EE:FF" (no quotes).

The most simple example would just printing out the name of what is 
being added.
A more complex example would be showing all of the details of the object.

Here's a more complex example using the Cobbler API.   Triggers don't 
have to use the Cobbler API, but if they want to interact with the 
Cobbler object tree, they can learn a lot by doing so...

Here's an example echo trigger -- 
/var/lib/cobbler/triggers/add/profile/echo.py -- I've left it rather 
short and compressed for demo purposes ... it can definitely be made a 
lot cleaner :)

#!/usr/bin/python

import sys
import cobbler.api as cobbler_api

if __name__ == "__main__":
    print sys.argv
    print cobbler_api.BootAPI().distros().find(sys.argv[1]).printable()


This was originally written as a suggestion from the Stateless Project 
(http://fedoraproject.org/wiki/StatelessLinux) -- if anyone has any 
suggestions on other things they might like triggers for, or questions 
about how they work,
please comment. 

For those interested in playing with the source, I've already pushed an 
initial version of the above ... "make rpms" will build cobbler, and 
install the RPM from the "rpm-build" directory...

--Michael DeHaan