Please allow me to generate the inventory_hostname

[cognifloyd]

SUMMARY

I would like to define my own formula for generating the inventory_hostname. As Azure does not allow renaming VMs, I need to use a tag to get our names for the VM. I want to use our standardize tag name so that I can add vars in host_vars/ as required.

ISSUE TYPE

• Feature Idea

COMPONENT NAME

azure_rm inventory plugin

ADDITIONAL INFORMATION

This is a continuation of ansible/ansible#54065 which only requested the ability to configure the legacy behavior.

I want to define my own inventory_hostname as mentiond here:

azure/plugins/inventory/azure_rm.py

Lines 366 to 368 in 4467d13

	def _get_hostname(self, host):
	# FUTURE: configurable hostname sources
	return host.default_inventory_hostname

For reference, this is the section that currently defines the legacy/unique hostname definition:

azure/plugins/inventory/azure_rm.py

Lines 504 to 508 in 4467d13

	if legacy_name:
	self.default_inventory_hostname = vm_model['name']
	else:
	# Azure often doesn't provide a globally-unique filename, so use resource name + a chunk of ID hash
	self.default_inventory_hostname = '{0}_{1}'.format(vm_model['name'], hashlib.sha1(to_bytes(vm_model['id'])).hexdigest()[0:4])

In both cases, this uses vm_model['name'] but I explicitly do NOT want to use vm_model['name'] because Azure doesn't let me rename VMs.

[cognifloyd]

Maybe one way to do this, would be to allow adding inventory_hostname to hostvar_expressions:

azure/plugins/inventory/azure_rm.py

Line 328 in 4467d13

constructable_config_compose = self.get_option('hostvar_expressions')

And do something like:

compose_inventory_hostname = constructable_config_compose.pop("inventory_hostname")

And pass that to get_hostname here:

azure/plugins/inventory/azure_rm.py

Line 333 in 4467d13

inventory_hostname = self._get_hostname(h)

inventory_hostname = self._get_hostname(h, compose_inventory_hostname, strict=constructable_config_strict)

Then _get_hostname would change to something like this:

def _get_hostname(self, host, compose=None, strict=False):
    if not compose:
        return host.default_inventory_hostname
    try:
        return self._compose(compose, h.hostvars)
    except Exception as e:
        if strict:
            raise AnsibleParserError("Could not generate inventory_hostname for host %s from hostvar_expressions.inventory_hostname: %s" % (host.default_inventory_hostname, to_native(e)))
        return host.default_inventory_hostname

Any comments on doing it like this? Or would using something other than hostvar_expressions be preferrable?

[mwinfie]

Can a maintainer review this? I think this would solve a similar issue we are having where we want to be able to pull in hosts by ip address instead of the vm name.

[Fred-sun]

Can a maintainer review this? I think this would solve a similar issue we are having where we want to be able to pull in hosts by ip address instead of the vm name

This PR has been reviewed and will be merged soon. Thank you!