Ansible 2.9 vs 2.10: Delegation in Role Tasks

Direct answers

1. Does delegate_to on a role task default to delegating the entire role in Ansible 2.10? Yes – the research brief indicates that starting with 2.10, a delegate_to set on a role include is interpreted as delegating the whole role unless an inner task explicitly overrides it.
2. How does variable scoping change when delegating at the task level between 2.9 and 2.10? In 2.9, delegate_to affects only the annotated task; variables (including facts) are evaluated on the host where the role is invoked. In 2.10, when the role is delegated, all role‑internal tasks inherit the delegated host for variable evaluation, shifting the scope to that host.
3. Is run_once required to avoid duplicate executions when delegating a role to the same host in 2.10? Adding run_once to the role include prevents the role from running multiple times when the same host appears repeatedly (e.g., in a loop). It is not strictly required if you guarantee no such duplication, but it is the recommended safeguard.

Confirmed facts (per research brief)

• In Ansible 2.9, delegate_to on a role task applies only to that task; the rest of the role runs on the original host.
• Ansible 2.10 retains the syntax but changes the default handling so that delegate_to on a role task is treated as delegating the entire role unless overridden.
• This change can cause duplicate execution of role tasks when the same host is targeted multiple times (e.g., via a loop); run_once on the role include mitigates the duplication.

Likely explanation (interpretation)

The shift likely stems from a refactor of role inclusion logic that now treats the role include as a single unit for delegation purposes. Consequently, any delegate_to attached to the include propagates to all tasks inside the role, altering where facts are gathered and where variables are resolved. When the delegated host matches the original host and the role is included in a loop, the role may be executed once per loop iteration on that host, leading to apparent duplicates unless run_once limits the execution to a single run.

Verification steps (minimal)

1. Create a role testrole with a task that prints inventory_hostname and a variable defined in vars/main.yml.
2. Write a playbook that includes the role with delegate_to: other_host and runs against a loop (e.g., with_items: [1,2]) on a target host.
3. Run the playbook with Ansible 2.9 and note the printed host and variable values (should reflect the original host).
4. Repeat with Ansible 2.10 (or a specific 2.10.x) and observe whether the output shows the delegated host for all role tasks.
5. Add run_once: yes to the role include and verify that, when looping, the task output appears only once per iteration.

Missing diagnostic detail

To confirm whether the behavior remains stable in your environment, please specify the exact Ansible 2.10.x patch version you are using, as later minor releases may have adjusted the delegation default.