Hello Xen API host plugin

I am about to call an OpenStack xen-api host plugin to ask my host to upload images to OpenStack glance. As I was exploring how to do that, I thought it would be a good time to write a Hello XenAPI host plugin example. You can read more about the XenAPI here:

• API reference
• XenAPI python binding
• OpenStack XenAPI Host plugins

Step 1: Create the host plugin

The host plugin should be an executable file on the host. In my case, it will be a simple python script. I choose the name “hi” for my plugin, so the plugin location is:

• On XCP or XenServer:

  /etc/xapi.d/plugins/hi

• On Debian/Ubuntu with xcp-xapi:

  /usr/lib/xcp/plugins/hi

The “hi” plugin looks like this:

#!/usr/bin/python

import XenAPIPlugin

def hello(session, arg_dict):
    name = arg_dict['name']
    return "Hello " + name + "!"

if __name__ == "__main__":
    XenAPIPlugin.dispatch(
        {"hello": hello}
    )

Don’t forget to make it executable:

chmod +x /usr/lib/xcp/plugins/hi

Step 2: call the host plugin

I will use the XenAPI python plugin for doing this. Start an interactive python session, and type in these things:

import XenAPI
session = XenAPI.Session('https://kronosmachine.somedomain')
session.login_with_password('root', 'megasecret')
host, = session.xenapi.host.get_all()
print session.xenapi.host.call_plugin(host, 'hi', 'hello', {'name' : 'OpenStack'})

You should see something like:

Hello OpenStack!

The session

The session parameter passed to your dispatched function is a xenapi session. So if you want to list the hosts, you could do it this way:

...
def hello(session, arg_dict):
    return repr(session.xenapi.host.get_all())
...

Again, for more information:

• XenAPI
• XenAPI python binding