EX294 Coordinate rolling updates Practice Question
An administrator is rolling out a configuration change to a fleet of 12 application servers. The change must be applied to one server at a time so that the load balancer always has 11 healthy backends. Which playbook directive guarantees this behavior?
⚠ Common exam trap
Test-takers frequently confuse task-level concurrency controls like throttle or forks with the play-level batch size set by serial.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
serial: 1
serial defines how many hosts Ansible includes in each rolling batch. Setting serial: 1 ensures the entire play finishes on one host before the next host begins, which keeps 11 of 12 servers available to the load balancer. Other keywords such as throttle and forks affect parallelism or task concurrency, but they do not create per-host rolling batches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
throttle: 1
Why it's wrong here
throttle limits the number of workers Ansible forks for a task, but it does not create host batches for the play. It controls concurrency at the task level, not the number of hosts updated per rolling batch. The fleet could still have multiple hosts in the same batch, so the load balancer might see more than one backend unavailable. serial is the correct directive for batch size.
- ✓
serial: 1
Why this is correct
serial: 1 instructs Ansible to process exactly one host per batch, so the play runs completely on one server before moving to the next. On a 12-node fleet, that leaves 11 servers untouched and available to the load balancer at all times. This directly satisfies the requirement of updating one server at a time without taking down capacity.
- ✗
order: sequential
Why it's wrong here
order is not a valid Ansible playbook keyword for controlling host batching. Ansible does not provide an order directive to serialize host execution. The correct mechanism for limiting how many hosts are processed at once is serial. Using order here would either be ignored or cause a syntax error, and it would not guarantee one-at-a-time updates.
- ✗
forks: 1
Why it's wrong here
forks is an Ansible configuration setting that limits parallel process execution, not a play-level batching directive. Setting forks to 1 slows execution but does not define the rolling update batch size. Hosts are still grouped into batches by serial, and without serial all hosts belong to one batch. The requirement for one-server-at-a-time updates is met by serial, not forks.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Red Hat exam blueprint
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