https://github.com/ansible-collections/amazon.aws/issues/556

1. 1. 1. Summary

The current implementation of ec2_inventory plugin is sorting the hosts by `InstanceId`. This is good enough to ensure stable ordering of the hosts within a `hostgroup` as long as no more nodes are added or deleted. However this implementation becomes an issue when the nodes in the group are not equal, for example, one node is supposed to be a master or initial node and treated differently than others.

With static inventories the problem has a simple solution: taking the first node of the group (e.g. `hostvars[groups['db_cluster'][0]]` where `db_cluster` includes `db1`, `db2` and `db3`). This doesn't work well with `aws_ec2_inventory` as the first node in the group could be any of the three.

One solution could be sorting the hostnames in-place, e.g. `db_primary_node: "{{ groups['db_cluster'] | sort | first }}"` however we would have to do this everywhere, in all playbooks, roles and inventories where we rely on the host order. Another slightly relevant problem is `run_once` implementation (and everything else that is using the same logic) which makes the tasks run only on the first node in the group but skipped if the first node is skipped (see https://github.com/ansible/ansible/issues/19966).

An easy fix for these would be an *option to sort hosts by their hostnames within a group*.

1. 1. 1. Issue Type

Feature Idea

1. 1. 1. Component Name

aws_ec2_inventory, ec2_inventory

1. 1. 1. Additional Information

A naive hard-coded implementation:
```python
diff --git a/collections/ansible_collections/amazon/aws/plugins/inventory/aws_ec2.py b/collections/ansible_collections/amazon/aws/plugins/inventory/aws_ec2.py
index 3806a0a2..113aba23 100644
— a/collections/ansible_collections/amazon/aws/plugins/inventory/aws_ec2.py
+++ b/collections/ansible_collections/amazon/aws/plugins/inventory/aws_ec2.py
@@ -615,7 +615,7 @@ class InventoryModule(BaseInventoryPlugin, Constructable, Cacheable):
instances.append
ids_to_ignore.append(i['InstanceId'])

• instances = sorted(instances, key=lambda x: x['InstanceId'])
  + instances = sorted(instances, key=lambda x: self._get_hostname(x, self.get_option('hostnames')))

return

```

1. 1. 1. Code of Conduct

• [X] I agree to follow the Ansible Code of Conduct