Examkin

Question

Difficulty: HardConfigure Virtual Machine Scale Sets (VMSS)

An administrator is configuring a Virtual Machine Scale Set (VMSS) named `vmss-api` that uses Uniform orchestration mode and a Rolling upgrade policy to host a web service. After deploying an application update by updating the VMSS model, the administrator observes that all instances are upgraded in sequence, but the web service becomes unavailable because the new version has a startup bug. The rolling upgrade did not pause or roll back because the VM provisioning status of the upgraded instances remained 'Succeeded'. You need to ensure that future rolling upgrades automatically pause and roll back if the web service fails to start on upgraded instances. What should you configure?

  1. An Application Health extension on the scale set to monitor the web service's health endpoint.Answer
  2. B
    A custom autoscale scale-in rule based on the average CPU usage of the scale set.
  3. C
    An Azure Monitor alert rule that triggers when the VM provisioning state changes to Succeeded.
  4. D
    A standard Azure Load Balancer with a TCP health probe associated with the scale set's backend pool, without enabling health-based upgrade orchestration on the scale set.

Answer

An Application Health extension on the scale set to monitor the web service's health endpoint.
The correct configuration is to use an Application Health extension on the scale set to monitor the web service's health endpoint. The Application Health extension is designed to run inside VMSS instances, monitor a configured HTTP/HTTPS or TCP endpoint, and report the application's health status back to the VMSS upgrade engine. During a rolling upgrade, this allows the engine to detect application-level failures, halt the rollout, and roll back to the previous model version.

Step-by-Step Solution

1
Analyze the upgrade behavior
The VMSS uses a Rolling upgrade policy but only monitors VM provisioning state, ignoring application-level health.
By default, Azure only monitors the VM fabric state (Succeeded) to determine health during upgrades unless configured otherwise.
2
Determine the application monitoring requirement
An application health signal must be provided to the VMSS upgrade engine.
To detect internal startup bugs (like HTTP 500 errors or port binding failures), health probes must evaluate the application itself.
3
Select the correct VMSS feature for rolling upgrade validation
Deploy the Application Health extension or configure health-based upgrade orchestration with a load balancer.
The Application Health extension directly monitors the local endpoint and coordinates with the VMSS upgrade orchestration engine to pause/rollback upgrades if health checks fail.

Key Concept

Configuring application health monitoring for Virtual Machine Scale Set (VMSS) rolling upgrades.
Estimated Time:2m 0s
Rate this question

Topics

Configure Virtual Machine Scale Sets (VMSS)

More questions from this topic