EX294 Coordinate rolling updates Practice Test 5 — 15 Questions

Question 1

An Ansible rolling update playbook has 'serial: 1' and 'max_fail_percentage: 0'. During the update of a 5-host group, the first host fails. What is the outcome?

Accepted Answer

The play aborts immediately. With 'serial: 1', Ansible updates one host at a time. 'max_fail_percentage: 0' means that if any host fails (0% failure tolerance), the entire playbook run is aborted immediately. When the first host fails, Ansible stops further execution because the failure percentage exceeds the threshold, and no retries or continuation occur.

Answer

The play pauses for manual intervention

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The play retries the failed host

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The play continues with the remaining 4 hosts

Answer

The play marks the host as unreachable and continues

Question 2

An OpenShift rolling update is failing because new pods crash immediately. Which parameter automatically triggers a rollback if no progress is made?

Accepted Answer

progressDeadlineSeconds. The `progressDeadlineSeconds` parameter specifies the maximum duration (in seconds) that a deployment can make no progress before it is considered to have failed. When this deadline is exceeded, the deployment controller automatically triggers a rollback to the previous revision. This is the correct parameter for automatically rolling back a failed rolling update where new pods crash immediately.

Answer

revisionHistoryLimit

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maxSurge

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maxUnavailable

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minReadySeconds

Question 3

A company uses Ansible to perform a rolling update of 10 web servers behind an HAProxy load balancer. The playbook uses the `serial` keyword and includes tasks to disable a host from the load balancer, update the web server package, and re-enable the host. Which TWO best practices should the administrator apply to minimize downtime and ensure a successful rolling update?

Accepted Answer

Set `serial: 1` to update one host at a time.. Setting `serial: 1` ensures that only one host is updated at a time, which is the safest way to perform a rolling update without overwhelming the load balancer or causing a service outage. This allows the playbook to complete the full update cycle (disable, update, re-enable) for each host before moving to the next, minimizing the number of hosts out of service simultaneously.

Answer

Use `any_errors_fatal: true` to stop the playbook if any host fails.

Answer

Use `throttle: 1` to limit the number of concurrent tasks across all hosts.

Answer

Use `async` and `poll` to run the update tasks in the background while proceeding to the next host immediately.

Question 4

You are performing a rolling update of a 12-node web server fleet managed by Ansible. The playbook uses `serial: 4`. During the second batch, the task `Restart httpd` fails on one host because the service name is misspelled. The playbook aborts with an error. You fix the typo and rerun the playbook. What is the default behavior regarding the hosts that were already updated successfully in the first batch?

Accepted Answer

The playbook starts over from the first batch and processes all hosts again, applying tasks to hosts that were already updated.. Ansible does not persist playbook progress between runs. When you rerun a playbook, it targets the entire inventory by default, so hosts from the first batch are processed again. To avoid re-updating already-successful hosts, you would need to use `--limit` with a list of remaining hosts or implement a custom serial strategy that records completed batches externally.

Answer

The playbook re-runs all tasks on every host, including the first batch, because Ansible is idempotent and will simply reapply the configuration.

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The playbook fails immediately because the inventory still marks the failed host as unreachable, blocking any further execution.

Answer

The playbook resumes from the failed batch, skipping the first batch entirely, because Ansible tracks successful hosts in a fact cache.

Question 5

An administrator is designing a rolling update playbook for a 20-node application cluster. The playbook must limit the blast radius of failures and allow the rollout to pause safely if too many hosts fail. Which two Ansible play-level keywords directly control how many hosts are updated at once and whether the play aborts based on failures? (Choose two.)

Accepted Answer

serial. serial controls how many hosts are processed in each rolling batch, directly limiting the blast radius. max_fail_percentage defines the failure threshold per batch that aborts the play, preventing the rollout from continuing when too many hosts fail. Together they provide the two controls the administrator needs for a safe rolling update.

Answer

forks

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order

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any_errors_fatal

Question 6

You are performing a rolling update on a 5-node application cluster using an Ansible playbook with `serial: 1`. The playbook includes a task that uses the `uri` module to check the application health endpoint after each node is updated. The health check must wait until the application returns HTTP 200 before proceeding to the next node. Which approach ensures that the playbook waits for the health check to succeed before moving to the next host?

Accepted Answer

Use the uri module with retries and until to repeatedly check the endpoint until it returns HTTP 200.. To ensure the playbook waits for the application to become healthy after each node update, you should use the uri module with retries and until. This combination repeatedly polls the health endpoint until it returns HTTP 200 or the retries are exhausted. This approach is reliable and ensures that the application is ready before proceeding to the next node in the rolling update.

Answer

Use the wait_for module with the host and port parameters to wait for the application to start listening.

Answer

Use the uri module with the status_code parameter set to 200 and register the result, then use a wait_for condition on the result.

Answer

Use the pause module to wait for a fixed amount of time after updating each node.

Question 7

You are designing a rolling update playbook for a 20-node application cluster. The application requires that no more than 25% of the nodes be unavailable at any time. You want Ansible to automatically pause the play if the failure rate within a batch exceeds a threshold, so that you can investigate before continuing. Which play-level keyword should you use?

Accepted Answer

`max_fail_percentage`. The `max_fail_percentage` keyword is designed to abort a play when the failure rate within a batch exceeds a given percentage. By setting it to 25, Ansible will stop the rolling update if more than 25% of the hosts in a batch fail, matching the application's availability requirement. This provides an automatic safety check during the update.

Answer

`serial`

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`any_errors_fatal`

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`ignore_errors`

Question 8

A junior administrator needs to perform a rolling update of 8 web servers where exactly 2 servers are updated at a time. Which play-level keyword and value should be used in the Ansible playbook?

Accepted Answer

serial: 2. The serial keyword is the standard way to define rolling update batch size in an Ansible play. Setting serial: 2 causes the play to process two hosts at a time through the full task list, ensuring only two of the eight web servers are updated concurrently. This is the direct and correct control for the administrator's requirement.

Answer

throttle: 2

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max_fail_percentage: 2

Answer

forks: 2

Question 9

You are writing an Ansible playbook to perform a rolling update of a 20-node RHEL application cluster. The application requires that no more than 20 percent of the fleet be offline at any time. You want the playbook to update hosts in batches that respect this constraint and to abort the entire rollout if the failure rate within any batch exceeds 10 percent. Which combination of play keywords should you use?

Accepted Answer

`serial: 20%` and `max_fail_percentage: 10`. The requirement is to cap concurrent offline hosts at 20 percent of the fleet while aborting when batch failures exceed 10 percent. With 20 nodes, 20 percent equals 4 hosts, so `serial: 20%` expresses the constraint as a percentage that scales with inventory size. `max_fail_percentage: 10` then aborts the play when more than 10 percent of the hosts in the current batch fail. Together they encode both the availability and failure-tolerance policies directly in the play.

Answer

`serial: 4` and `max_fail_percentage: 25`

Answer

`serial: 4` and `max_fail_percentage: 10`

Answer

`serial: 20` and `max_fail_percentage: 10`

Question 10

A platform team uses an Ansible playbook with 'serial: "20%"' to roll out a new configuration to 50 hosts. During the third batch, a task fails on several hosts, and the play aborts with a message about max_fail_percentage. Which statement correctly describes how Ansible determined the batch size and the failure threshold in this run?

Accepted Answer

The batch size was 10 hosts, and the failure threshold was evaluated against the 10 hosts in the current batch.. When serial is a percentage, Ansible multiplies that percentage by the total number of hosts in the play to determine each batch size. For 50 hosts at 20%, each batch contains 10 hosts. max_fail_percentage is then evaluated against the current batch, so the abort decision is based on failures among those 10 hosts, not the full inventory.

Answer

The batch size was 5 hosts, and the failure threshold was evaluated against the 5 hosts in the current batch.

Answer

The batch size was 20 hosts, and the failure threshold was evaluated against 50 hosts.

Answer

The batch size was 10 hosts, and the failure threshold was evaluated against all 50 hosts regardless of batch.

Question 11

You are performing a rolling update of a 6-node RHEL web server fleet using an Ansible playbook. The playbook currently uses `serial: 1` and takes a long time because each host is updated sequentially. You want to update two hosts at a time to reduce the total rollout duration while still keeping at least four hosts serving traffic. Which change should you make?

Accepted Answer

Change `serial: 1` to `serial: 2`.. To update two hosts at a time in a six-node fleet while keeping four hosts online, the serial batch size must be two. Changing serial from 1 to 2 directly controls how many hosts Ansible targets per play iteration, halving the number of batches and shortening the rollout. Other keywords such as throttle and forks affect concurrency of task execution but do not define rolling update batch boundaries.

Answer

Add `forks: 2` to the play.

Answer

Change `serial: 1` to `serial: 4`.

Answer

Add `throttle: 2` to the play.

Question 12

You are running an Ansible playbook with `serial: 2` to update a fleet of 6 web servers. The playbook includes a task that restarts the web service. After the first batch of 2 hosts is updated, you notice that both hosts are restarted simultaneously. You want to ensure that within each batch, the hosts are updated one at a time to avoid a temporary loss of capacity. Which Ansible keyword should you add to the play to achieve this?

Accepted Answer

`throttle: 1` on the restart task. The `throttle` keyword limits the number of concurrent executions of a task across all hosts. By setting `throttle: 1` on the restart task, you ensure that only one host restarts the web service at a time, even within a batch of 2. This maintains the rolling update's goal of minimizing downtime while keeping the batch size efficient.

Answer

`order: inventory` at the play level

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`serial: 1` at the play level

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`strategy: linear` at the play level

Question 13

You are performing a rolling update of a 15-node RHEL cluster with an Ansible playbook that uses `serial: 5`. During the second batch, a host fails to restart its application service, and the task fails. You want the playbook to stop the entire rollout immediately so that no further batches are updated, allowing you to investigate the failure. Which play keyword should you set to achieve this behavior?

Accepted Answer

`any_errors_fatal: true`. To stop the entire play immediately when any task fails on any host, the play must set any_errors_fatal to true. This keyword overrides the default behavior where a failed host is removed and other hosts continue, causing the whole run to abort as soon as the failure occurs. It is the correct mechanism for halting a rolling update on the first error.

Answer

`max_fail_percentage: 0`

Answer

`ignore_errors: false` on the service restart task.

Answer

`serial: 1`

Question 14

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?

Accepted Answer

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

throttle: 1

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order: sequential

Answer

forks: 1

Question 15

You are designing a rolling update for a stateful service where each node must be removed from a load balancer, updated, and re-added before the next node is touched. The update must never take more than one node offline at a time, and if the update fails on a node, the play must stop and leave the remaining nodes untouched. Which playbook configuration achieves this?

Accepted Answer

serial: 1 with any_errors_fatal: true and tasks ordered to drain, update, and re-add within the same play.. Ensuring only one node is offline at a time and halting on failure requires a batch size of one and play-level fatal error handling. serial: 1 isolates each node, while any_errors_fatal: true stops the play immediately on any failure, leaving the remaining nodes untouched and still in rotation.

Answer

serial: 1 with ignore_errors: true on the update task so the play can continue to the next node.

Answer

serial: 2 with max_fail_percentage: 50 so that one failure in a batch is tolerated and the play continues.

Answer

serial: 1 with run_once: true on the drain and re-add tasks so they execute only once per batch.