Composing inventory_hostname manually

[aobertyshev]

Summary

Here is my current config:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostnames:
  - tag:Name
compose:
  ansible_host: private_ip_address

Executing it sets inventory_hostname variable(s) to the "Name" tag value. However, I would like to know whether it's possible to create a completely custom inventory_hostname, as I haven't found a clear way to do it by searching through the docs (as far as I understood it's only allowed to use the values from here which doesn't suit my case).

I have an AWS cloud and an Azure cloud, which serves as a mirror of the AWS cloud. The VMs on both clouds are named similarly (e.g. "prometheus"). I would like to refer to these VMs as 'aws-prometheus' and 'azu-prometheus'. The azure_rm plugin allows creating custom inventory_hostname:

hostnames:
  - "'azu-' + name"

, where "name" is just a key in the object returned by the API (like 'private_ip_address' for AWS). This way, I can refer to Azure VMs with 'azu-' prefix.

I would like to know whether it's possible to do the same with the aws_ec2 plugin. I've played around with different combinations and values for 'hostnames' but found myself limited with the values allowed by AWS.

This doesn't work because "aws-" is not a recognized value from here:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostnames:
  - name: "tag:Name"
    prefix: "aws-"
compose:
  ansible_host: private_ip_address

Thank you in advance.

Issue Type

Feature Idea

Component Name

amazon.aws.aws_ec2

Additional Information

No response

Code of Conduct

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[aobertyshev]

Thank you, frankly I expected it was me not being able to do this properly rather than this feature missing :)

I had a quick look through the PR, do I understand correctly that a new config would look like this:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostnames:
  - name: "tag:Name"
    prefix: "aws-"
compose:
  ansible_host: private_ip_address

or like this:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostnames:
  - name: "tag:Name"
    separator: "-"
    prefix: "aws"
compose:
  ansible_host: private_ip_address

E.g. I have a machine on AWS with the tag "Name" of value "prometheus".
Would both of these configs make it possible to refer to this VM as "aws-prometheus" in the playbooks?

Thank you in advance.

[jatorcasso]

Thank you, frankly I expected it was me not being able to do this properly rather than this feature missing :)

I had a quick look through the PR, do I understand correctly that a new config would look like this:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostnames:
  - name: "tag:Name"
    prefix: "aws-"
compose:
  ansible_host: private_ip_address

or like this:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostnames:
  - name: "tag:Name"
    separator: "-"
    prefix: "aws"
compose:
  ansible_host: private_ip_address

E.g. I have a machine on AWS with the tag "Name" of value "prometheus". Would both of these configs make it possible to refer to this VM as "aws-prometheus" in the playbooks?

Thank you in advance.

Just double checked and you should be able to use the hostvars_prefix! So, that would look like:

...
hostvars_prefix: 'aws-'
hostnames:
  - name: "tag:Name"
...

Let me know if that works for you! This feature was added in version 3.1.0

If using hostvars_prefix isn't enough (since it only prefixes the names of AWS variables), then to use the linked PR, you would use either:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostnames:
  - name: "tag:Name"
    prefix: "aws-"
    separator: ''
compose:
  ansible_host: private_ip_address

or like this:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostnames:
  - name: "tag:Name"
    separator: "-"
    prefix: "aws"
compose:
  ansible_host: private_ip_address

since the default for separator is _

[aobertyshev]

Thank you for the fast reply.

hostvars_prefix is, per documentation, The prefix for host variables names coming from AWS.
So, having the following config:

---
plugin: amazon.aws.aws_ec2
regions:
  - eu-central-1
hostvars_prefix: "aws-"
hostnames:
  - tag:Name

and executing the following command:
ansible-inventory -i inventory/aws_ec2.yml --list
returned:

While it does what is stated in the documentation, it doesn't alter the hostname itself, which is my use case (and, of course, I'd like to keep the original var names). Thus, eagerly waiting for this PR to get merged :)