Displaying a custom name for a host

Question

I have an Ansible play-book for working with EC2 instances. I'm using dynamic inventory (ec2.py) to get the group of instances that I want to work with (hosts: tag_Service_Foo). When I run it, it produces output like:

GATHERING FACTS ***************************************************************
ok: [54.149.9.198]
ok: [52.11.22.29]
ok: [52.11.0.3]

However, I can fetch the "Name" tag for a particular instance from Amazon (I do this and store it in a variable for use in a couple parts of the playbook).

Is there a way to get Ansible to use this string for the hostname when displaying progress? I'd like to see something more descriptive (since I don't have the IPs memorized):

GATHERING FACTS ***************************************************************
ok: [main-server]
ok: [extra-server]
ok: [my-cool-server]

The output of the ec2.py inventory script looks like this (truncated; it's very long).

{
  "_meta": {
    "hostvars": {
      "54.149.9.198": {
        "ec2__in_monitoring_element": false,
        "ec2_ami_launch_index": "0",
        "ec2_architecture": "x86_64",
        "ec2_client_token": "xxx",
        "ec2_dns_name": "xxx",
        "ec2_ebs_optimized": false,
        "ec2_eventsSet": "",
        "ec2_group_name": "",
        "ec2_hypervisor": "xen",
        "ec2_id": "i-xxx",
        "ec2_image_id": "ami-xxx",
        "ec2_instance_type": "xxx",
        "ec2_ip_address": "xxx",
        "ec2_item": "",
        "ec2_kernel": "",
        "ec2_key_name": "xxx",
        "ec2_launch_time": "xxx",
        "ec2_monitored": xxx,
        "ec2_monitoring": "",
        "ec2_monitoring_state": "xxx",
        "ec2_persistent": false,
        "ec2_placement": "xxx",
        "ec2_platform": "",
        "ec2_previous_state": "",
        "ec2_previous_state_code": 0,
        "ec2_private_dns_name": "xxx",
        "ec2_private_ip_address": "xxx",
        "ec2_public_dns_name": "xxx",
        "ec2_ramdisk": "",
        "ec2_reason": "",
        "ec2_region": "xxx",
        "ec2_requester_id": "",
        "ec2_root_device_name": "/dev/xvda",
        "ec2_root_device_type": "ebs",
        "ec2_security_group_ids": "xxx",
        "ec2_security_group_names": "xxx",
        "ec2_sourceDestCheck": "true",
        "ec2_spot_instance_request_id": "",
        "ec2_state": "running",
        "ec2_state_code": 16,
        "ec2_state_reason": "",
        "ec2_subnet_id": "subnet-xxx",
        "ec2_tag_Name": "main-server",
        "ec2_tag_aws_autoscaling_groupName": "xxx",
        "ec2_virtualization_type": "hvm",
        "ec2_vpc_id": "vpc-xxx"
      }
    }
  }
  "tag_Service_Foo": [
    "54.149.9.198",
    "52.11.22.29",
    "52.11.0.3"
  ],
}

Answer 1

What you need to do is create your own wrapper (say my_ec2.py) over the ec2.py that would post process the output. Idea is to use the behavioral hostvar ansible_ssh_host. You can use any language not only python. As long as it prints valid json on stdout you're good to go. Reference if needed.

It'll be a tiny bit of work. But hope the sudo code would help:

output_json_map = new map
for each group in <ec2_output>: # e.g. tag_Service_Foo, I think there would be another 
                                # key in the output that contains list of group names.
  for each ip_address in group:
    hname = ec2_output._meta.hostvars.find(ip_address).find(ec2_tag_Name)

    # Add new host to the group member list
    output_json_map.add(key=group, value=hname)
    copy all vars from ec2_output._meta.hostvars.<ip_address>
                  to output_json_map._meta.hostvars.<hname>
    # Assign the IP address of this host to the ansible_ssh_host
    # in hostvars for this host
    output_json_map.add(key=_meta.hostvars.<hname>.ansible_ssh_host,
                        value=ip_address)
    output_json_map.add(key=_meta.hostvars.find(ip_address).ansible_ssh_host,
                        value=ip_address)

print output_json_map to stdout

E.g. for your example the output of my_ec2.py should be:

{
  "_meta": {
    "hostvars": {
      "main-server": {
        "ansible_ssh_host": "54.149.9.198"
        --- snip ---
        "ec2_tag_Name": "main-server",
        --- snip ---
      },
      "extra-server": {
        "ansible_ssh_host": "52.11.22.29"
        --- snip ---
        "ec2_tag_Name": "extra-server",
        --- snip ---
      },
      <other hosts from all groups>
    }
  }
  "tag_Service_Foo": [
    "main-server",
    "extra-server",
    <other hosts in this group>
  ],
  "some other group": [
    <hosts in this group>,
    ...
  ],
}

and obviously, use this my_ec2.py instead of ec2.py as the inventory file. :-)

-- edit --

1) In the groups, can I only refer to things by one name? 2) There's no notion of an alias? 3) I'm wondering if I could use the IP addr in the groups and just modify the _meta part or if I need to do it all?

Yes*, No and no.

---

* Technically first yes should be no. Let me explain.

What we are doing here can be done with static inventory file like this:

Original ec2.py was returning json equivalent of following inventory file:

[tag_Service_Foo]
54.149.9.198 ec2_tag_Name="main-server"  ec2_previous_state_code="0" ...
52.11.22.29  ec2_tag_Name="extra-server" ec2_previous_state_code="0" ...

our new my_ec2.py returns this:

[tag_Service_Foo]
main-server  ansible_ssh_host="54.149.9.198" ec2_tag_Name="main-server"  ec2_previous_state_code="0" ...
extra-server ansible_ssh_host="52.11.22.29"  ec2_tag_Name="extra-server" ec2_previous_state_code="0" ...

# Technically it's possible to create "an alias" for main-server like this:
main-server-alias  ansible_ssh_host="54.149.9.198" ec2_tag_Name="main-server"  ec2_previous_state_code="0" ...

Now you would be able to run a play with main-server-alias in the host list and ansible would execute it on 54.149.9.198.

BUT, and this is a big BUT, when you run a play with 'all' as the host pattern ansible would run the task on main-server-alias as well as main-server. So what you created is an alias in one context and a new host in another. I've not tested this BUT part so do come back and correct me if you find out otherwise.

HTH

Answer 2

If you put

vpc_destination_variable = Name

in your ec2.ini file, that should work too.