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Zorluk: ZorConfigure Virtual Machine Scale Sets (VMSS)

You are configuring an Azure Virtual Machine Scale Set (VMSS) named `vmss-processor` that processes messages from an Azure Service Bus queue. The VMSS is configured with the following parameters:
- Orchestration mode: Flexible
- Upgrade policy: Manual
- Current instance count: 4
- Scale-in policy: Default

You need to configure autoscale rules to meet the following requirements:
1. Scale out by 2 instances when the average queue depth exceeds 1,000 messages.
2. Scale in by 1 instance when the average queue depth falls below 200 messages.
3. Prevent instance thrashing (frequent, consecutive scale-out and scale-in actions).

Which of the following configurations should you apply to the autoscale rules? (Select TWO.)

  1. Configure the scale-out rule with a threshold of 1,000 messages and the scale-in rule with a threshold of 200 messages.Cevap
  2. Configure a cooldown period of 10 minutes for both the scale-out and scale-in rules.Cevap
  3. C
    Configure the scale-in rule with a threshold of 950 messages to quickly terminate idle instances after workload spikes.
  4. D
    Set the cooldown period to 0 minutes for the scale-in rule to ensure immediate deprovisioning of instances.

Cevap

To configure the VMSS autoscale rules correctly, you should configure the scale-out threshold to 1,000 messages and the scale-in threshold to 200 messages, and configure a cooldown period of 10 minutes for both rules.
Establishing a wide gap between the scale-out threshold of 1,000 messages and the scale-in threshold of 200 messages prevents rapid fluctuations in queue depth from triggering conflicting scale actions. Additionally, setting a cooldown period of 10 minutes ensures that Azure Monitor allows the VMSS to stabilize and the queue metrics to catch up after a scale action before evaluating the rules again.

Adım Adım Çözüm

1
Analyze the scaling thresholds to prevent thrashing.
Identify that the scale-out threshold is 1,000 messages and the scale-in threshold must be significantly lower, such as 200 messages.
If the thresholds are set too close to each other, the added processing capacity from a scale-out event will immediately lower the queue depth below the scale-in threshold, initiating an loop of constant instance provisioning and deprovisioning.
2
Determine the appropriate cooldown settings for the autoscale rules.
Set a cooldown period (e.g., 10 minutes) for both rules.
The cooldown period prevents the scale set from executing consecutive scaling decisions without giving the newly created or remaining instances enough time to start up and stabilize the workload metrics.

Anahtar Kavram

Virtual Machine Scale Set (VMSS) Autoscale Rules and Thrashing Prevention
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Konular

Configure Virtual Machine Scale Sets (VMSS)

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