Prototype code for tracking virtual machines and their dependencies (eg. NFS client VMs depend on a NFS server VM)

vm_tracker

#!/usr/bin/env python

class VirtualMachines(object):

    def __init__(self):
        self.virtual_machines = {}

    def add_vm(self, name, vm_dom, dependencies=[]):
        """Add a virtual machine domain entry

        Arguments:
        name -- should match libvirt.virDomain.name
        vm_dom -- libvirt.virDomain instance
        dependencies -- list of vm_dom names
        """
        print "ADDING %s" % name
        self.virtual_machines.update(
            {
                name: {
                    'vm_dom': vm_dom,
                    'dependencies': []
                }
            }
        )
        for dependency in dependencies:
            self.add_dependency_by_name(name, dependency)

    def rem_vm(self, name):
        """Delete a virtual machine domain entry"""
        print "REMOVING %s" % name
        del(self.virtual_machines[name])

    def get_vm_dom(self, name):
        """Return a virtual machine domain if it exists"""
        result = None
        if name in self.virtual_machines:
            result = self.virtual_machines[name][vm_dom]
        return result

    def add_dependency_by_name(self, name, dependency):
        """Add virtual machine domain dependencies referencedd by name"""
        if name not in self.virtual_machines:
            raise ValueError(
                "Cannot add dependency to unknown virtual machine " + \
                "'{}'\n".format(name)
            )
        elif dependency not in self.virtual_machines:
            raise ValueError(
                "Cannot add unknown dependency for '{}'\n".format(name)
            )
        elif name == dependency:
            raise ValueError(
                "'{}' cannot depend on itself\n".format(name)
            )
        else:
            self.virtual_machines[name]['dependencies'].append(
                dependency
            )

    def get_dependency_names(self, name):
        """Returns a list of dependency virtual machine names for name"""
        return self.virtual_machines[name]['dependencies']


vm = VirtualMachines()

vm.add_vm('vm0', None)
vm.add_vm('vm1', None)

vm.rem_vm('vm1')
print "Currently {} record(s).".format(len(vm.virtual_machines))

vm.add_vm('vm2', None)
vm.add_vm('vm3', None)
vm.add_dependency_by_name('vm2', 'vm0')
vm.add_dependency_by_name('vm2', 'vm3')

print "vm2 dependencies: %r" % vm.get_dependency_names('vm2')

# Explode:
vm.add_dependency_by_name('vm2', 'vm1')
print "vm2 dependencies: %r" % vm.get_dependency_names('vm2')