EX294 Coordinate rolling updates — Timed 10 Questions

Question 1

A company uses Ansible to manage rolling updates of a web server fleet. During a deployment, the playbook fails on one host due to a transient network error, and the rest of the fleet is left in an inconsistent state. Which strategy would best minimize the risk of inconsistency in future rolling updates?

10 minute time limit — choose an answer to begin.

Accepted Answer

Set max_fail_percentage to 0 in the serial block to abort the rollout on any failure.. Setting `max_fail_percentage: 0` in a rolling update (using `serial`) tells Ansible to abort the entire playbook run if any single host fails. This prevents the rest of the fleet from being updated, avoiding an inconsistent state where some hosts have the new deployment and others do not. It directly addresses the risk of partial rollouts caused by transient errors.

Answer

Add retries to each task so transient errors are automatically retried.

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Use a larger serial batch size to complete the rollout faster.

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Set ignore_errors: yes on all tasks to continue despite failures.

Question 2

An operations team is designing a rolling update for a stateful application that requires quorum (minimum 3 out of 5 nodes online). They plan to use Ansible's serial keyword. Which serial value ensures the update proceeds without breaking quorum while still being efficient?

Accepted Answer

serial: 2. Setting serial: 2 ensures that only 2 nodes are taken down at a time during the rolling update. With a quorum requirement of 3 out of 5 nodes, taking down 2 nodes leaves 3 online, maintaining quorum. This is the most efficient value that does not risk breaking quorum.

Answer

serial: 1

Answer

serial: 3

Answer

serial: 5

Question 3

Which TWO options are best practices for coordinating rolling updates with Ansible? (Choose exactly two.)

Accepted Answer

Use the serial keyword to update hosts in batches.. The `serial` keyword in Ansible controls how many hosts are updated at a time during a rolling update, allowing you to update hosts in batches to maintain service availability. This is a best practice for coordinating rolling updates as it prevents overwhelming the infrastructure and ensures that a subset of hosts remains operational while others are being updated.

Answer

Set ignore_errors: yes to ensure the playbook continues even if some hosts fail.

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Use the default serial setting (all hosts) for simplicity.

Answer

Run all hosts in parallel to minimize total update time.

Question 4

Refer to the exhibit. The playbook uses serial: 1 (one host at a time). The update failed on web3.example.com. Based on the output, what is the most likely reason the play did not abort the rollout and how should the playbook be modified to stop on failure?

Accepted Answer

Add max_fail_percentage: 0 to the play to abort on any failure.. The play uses `serial: 1` to update one host at a time, but by default Ansible continues to the next host even if a task fails on the current host. Setting `max_fail_percentage: 0` at the play level tells Ansible to abort the entire play immediately if any host fails, which is the intended behavior for a rolling update where a single failure should stop the rollout.

Answer

Add retries: 3 to the 'Update Apache config' task.

Answer

Set ignore_errors: yes on the 'Update Apache config' task.

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Increase the serial value to update multiple hosts at once.

Question 5

You are managing a rolling update of a 10-node web application cluster using Ansible. The application requires that at least 8 nodes remain available during the update to handle traffic. You have written a playbook that uses serial: 2 (updates 2 nodes at a time). During a test run, the playbook updates the first batch of 2 nodes successfully, but when it proceeds to the second batch, one of the nodes fails to restart the web service. However, the playbook continues and updates the remaining nodes. At the end, only 7 nodes are healthy, causing performance degradation. You need to ensure that if a batch fails to meet the minimum health requirements, the entire rollout is stopped and no further updates are applied. Which course of action should you take?

Accepted Answer

Use a rolling update strategy with serial: 2 and a post-task health check, and set max_fail_percentage to abort the play if the healthy node count drops below 8.. This approach uses `max_fail_percentage` at the play level to abort the playbook if a certain percentage of tasks fail. Combined with a post-task health check that fails when fewer than 8 nodes are healthy, the playbook stops if the healthy node count drops below the required threshold, preventing further updates and performance degradation. The `serial: 2` ensures nodes are updated in batches, and the health check verifies the minimum healthy count after each batch.

Answer

Add a retry loop to the service restart task with a delay and count of 5.

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Set ignore_errors: yes on the service restart task to avoid failures stopping the playbook.

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Increase serial to 3 to complete the update faster and reduce the chance of node failures.

Question 6

An Ansible Engineer is planning a rolling update for a web application deployed across 10 nodes. The playbook uses the 'delegate_to' directive to manage load balancer health checks. Which of the following best describes the recommended approach to minimize downtime?

Accepted Answer

Use 'serial: 1' and delegate load balancer disable/enable tasks to localhost, ensuring each node is taken out of rotation before updating.. Using 'serial: 1' ensures that only one node is updated at a time, and delegating load balancer disable/enable tasks to localhost (or the Ansible control node) allows the playbook to interact with the load balancer API to remove the node from the pool before the update and re-add it after. This minimizes downtime by ensuring traffic is not sent to a node being updated, while other nodes continue serving requests.

Answer

Run the update playbook with 'serial: 10' to update all nodes at once, then run a separate playbook to update the load balancer.

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Run the update on each node manually using 'ansible-playbook --limit' and skip load balancer management to save time.

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Use 'strategy: free' to allow nodes to update independently without controlling the load balancer.

Question 7

Which TWO of the following are best practices when coordinating rolling updates with Ansible?

Accepted Answer

Define a 'max_fail_percentage' to abort the update if too many hosts fail.. 'max_fail_percentage' allows you to define a threshold of host failures (as a percentage of the batch size) that, when exceeded, causes Ansible to abort the entire rolling update. This prevents the update from continuing when too many hosts have failed, which could lead to an inconsistent or degraded state across the infrastructure. Option B is correct because the 'serial' keyword controls the number of hosts (or percentage) that Ansible updates in each batch, ensuring that only a subset of hosts is taken out of service at a time, which maintains overall service availability during the rolling update.

Answer

Use 'strategy: free' to allow hosts to run tasks independently.

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Use 'gather_facts: no' to speed up the playbook.

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Set 'any_errors_fatal: true' to stop the update on the first failure.

Question 8

A team runs the playbook shown in the exhibit. They notice that during the update, some requests are still being sent to servers that have been disabled. What is the most likely cause?

Accepted Answer

The 'serial: 2' setting allows two hosts to be disabled simultaneously, and the load balancer may not have drained connections.. The `serial: 2` setting causes Ansible to update two hosts at a time. When a host is disabled in the load balancer, existing connections may not be fully drained before the next batch of hosts is updated, allowing traffic to still reach disabled servers. The load balancer needs time to drain active sessions, and a serial batch of 2 can overlap with that drain window.

Answer

The disable task should use 'state: maintenance' instead of 'state: disabled'.

Answer

The 'delegate_to' should be set to localhost, not lb01.

Answer

The 'serial' keyword is incorrectly used as a global variable.

Question 9

An administrator needs to update a web application that runs as a Kubernetes Deployment with 5 replicas. The application is stateless, but the update must not cause any downtime. Which TWO strategies ensure zero-downtime rolling updates?

Accepted Answer

Set strategy type to RollingUpdate with maxUnavailable=0 and maxSurge=1.. Setting `maxUnavailable=0` ensures that no pods are taken down before new ones are ready, while `maxSurge=1` allows one extra pod to be created above the desired replica count, enabling a rolling update without any downtime. This combination guarantees that at least 5 pods are always available during the update process.

Answer

Omit the liveness probe from the pod spec.

Answer

Set maxUnavailable=1 and maxSurge=0.

Answer

Use the Recreate strategy.

Question 10

You are managing a Kubernetes cluster running a critical stateful application deployed as a StatefulSet with 3 replicas. The application uses persistent volumes with ReadWriteOnce access mode. You need to update the container image from version 1.0 to 1.1. The application's performance degrades if more than one replica is unavailable at any time. The StatefulSet is configured with the default RollingUpdate strategy (partition=0). You have a maintenance window of 30 minutes. The update must be completed within the window with minimal risk. Which of the following approaches should you take?

Accepted Answer

Use the default rolling update with partition=0; the StatefulSet will update one pod at a time automatically.. The default RollingUpdate strategy with partition=0 updates one pod at a time, ensuring that no more than one replica is unavailable at any moment. This matches the application's constraint that performance degrades if more than one replica is unavailable, and the 30-minute window is sufficient for a rolling update of 3 pods.

Answer

Manually delete each pod and let the StatefulSet recreate them with the new image.

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Set maxUnavailable to 2 to speed up the rollout, then update the image.

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Perform a canary update by setting partition to 2, updating one pod, validating, then setting partition to 0.