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Exam AZ-104 topic 4 question 96 discussion

Actual exam question from Microsoft's AZ-104

Question #: 96
Topic #: 4

You have an Azure App Service app named App1 that contains two running instances.

You have an autoscale rule configured as shown in the following exhibit.

For the Instance limits scale condition setting, you set Maximum to 5.

During a 30-minute period, App1 uses 80 percent of the available memory.

What is the maximum number of instances for App1 during the 30-minute period?

A. 2
B. 3
C. 4
D. 5

Show Suggested Answer

Suggested Answer: D 🗳️

by [deleted] at Sept. 1, 2023, 6:26 a.m.

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athli

Highly Voted 1 year, 10 months ago

Selected Answer: D

Start at 2 instances, after 15 min, > 70%, then +1 instance Cooling 5 mins, still >70%, then +1 instance Cooling 5 mins, still > 70%, then +1 instance Cooling 5 mins, still >70%, since max 5 instances, keep 5 instances only

upvoted 114 times

Jacky_exam

1 year, 7 months ago

Minute 0-15: Memory usage exceeds 70%. Autoscale rule triggered. Instance count increased by 1 (from 2 to 3). Cooldown period starts. Minute 15-20 (Cooldown Period): No further scaling can occur during the cooldown period. Minute 20-30: Memory usage continues to exceed 70%, but the cooldown is still in effect. No further scaling during this time.

upvoted 23 times

Hispan

1 year, 3 months ago

chatgpt: Let’s calculate the number of CPU cores based on the provided information: Initial CPU Cores: 2 Scale-Out Rule: When CPU usage exceeds 80% for 15 minutes, scale out by 1 core. Cooldown period after scaling: 5 minutes. Given that the CPU usage has been above 80% for 30 minutes, let’s break it down: First 15 minutes: CPU usage exceeds 80%, so we scale out by 1 core. Total cores after the first 15 minutes: 2 (initial) + 1 (scaled out) = 3 cores. Next 15 minutes (with cooldown): During this period, no further scaling occurs due to the cooldown. Total cores remain at 3 cores. Therefore, after 30 minutes of continuous high CPU usage, you will have 3 CPU cores.

upvoted 14 times

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Dankho

9 months, 1 week ago

Completely correct, we have to remember that the original duration is used the first or if it resets because the number went below the threshold to trigger scale action. If it never goes below at any point, then we just wait for Cool Down and then reevaluate again or add another instance. I actually messed up again and used the duration but that is an error.

upvoted 2 times

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217972f

1 year, 1 month ago

here a reference about "look back": https://learn.microsoft.com/en-us/azure/azure-monitor/autoscale/autoscale-understanding-settings#autoscale-evaluation

upvoted 2 times

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2a742bc

1 year, 2 months ago

This is correct according to this article: https://cloudbuild.co.uk/azure-virtual-machine-scale-set-duration-and-cool-down-explained/

upvoted 5 times

6582fb2

10 months, 2 weeks ago

According to the link above, the CPU status will be collected during cooling time (5mins) so if the instance starts with 2, after 15mins, it will add 1, which is total 3 Then since 5 mins cooling (only mean wont scale in or scale out, but still collecting status >70%), then wait another 10 mins on top of 5 mins cooling ( total 15 mins, still above 70%), it will add another instances. So total 4 instances after 30 mins.

upvoted 2 times

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altairezio

Highly Voted 1 year, 10 months ago

Selected Answer: B

2 instances then after 15min : 3 instances. After 5min cooldown start counting. So correct answer : 3 instances

upvoted 61 times

ki01

1 year, 7 months ago

Answer D. for the scaler to kick in, it needs to be 15 minutes of average use above x % that is set. so once the load starts, it will wait 15 minutes until that rule is met, and a scale up will happen. once it scales up at the 15 minute mark, the 5 minute cooldown starts. at 20 minute mark, the scaler will LOOK BACK at the PAST 15 minutes to see if during that time the usage was still higher than x% and scale up again. then it will wait another 5 minutes, check the PAST 15 minutes again, scale up again, etc. etc. the previous performance data doesnt get thrown out after each scale, it keeps on sliding the dataset its checking forward. imagine if this was a real app and you get hit by huge traffic surge. like your company release a new product. what this would do in your method is scale up one instance every 20 minutes, so it might mean multiple hours of degraded performance while it catches up to demand, while the reality and my explanation, it would kick in after 15 minutes and then keep scaling every 5 minutes which is a much faster and reasonable solution.

upvoted 12 times

binhdortmund

1 year, 5 months ago

correct! I wanna go with 3 at the beginning, but after reading the MS doc and also your text, 5 is my choice

upvoted 3 times

mamamamn

1 year, 4 months ago

Would you please share the link? I still dont get it.

upvoted 1 times

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FlaShhh

1 year, 5 months ago

well explained

upvoted 1 times

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Batiste2023

1 year, 8 months ago

No, if after the cool down period the threshold is stil met, then the next scale out operation will happpen immediately (followed by another cool down period, of course). "The cooldown period for each rule dictates how long after the previous scale action (whatever rule initiated was), the rule can be applied." Source: https://github.com/MicrosoftDocs/azure-docs/issues/17169

upvoted 2 times

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Manu1986

Most Recent 3 weeks, 1 day ago

Selected Answer: B

At Time 15 minutes: The first scale-out action is triggered. Instances increase by 1: 2 + 1 = 3 instances. A cool-down period of 5 minutes begins immediately. During cool-down, no new scale-out actions can be triggered. Time 15 minutes to Time 20 minutes (Cool-down period): Instances: 3 Memory usage is still 80%. No further scale-out action can occur during this 5-minute cool-down. At Time 20 minutes: The cool-down period ends. The autoscale engine resumes evaluation. Memory usage is still 80%. For a new scale-out action to trigger, the condition (80% > 70%) must be met for another consecutive 15 minutes after the cool-down ends. Time 20 minutes to Time 30 minutes: Instances: 3 Memory usage remains at 80%. A new 15-minute duration period for a second scale-out would start counting from Time 20 minutes. It would only complete at Time 20 + 15 = Time 35 minutes.

upvoted 1 times

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Carlos_Naty

1 month, 1 week ago

Selected Answer: B

So many of you are getting this all mixed up. Note that after the count down period, the system doesn't automatically scale, a new cycle as to begin on top of the count down before another scaling can occur, provided the CPU % is still higher than 70%. so Initial instances = 2, at 15mins instance count increases by 1, count down begins, after count down, we are not at 20min, the system start evaluating again, after 15mins, we are now at 35mins, nothing happens since the time in question is 30mins. This makes a total of 3 instances.

upvoted 3 times

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SBGM

3 months, 1 week ago

Selected Answer: D

Answer is D. Documentation states 'After a scale action occurs, the autoscale job waits for the cooldown period before it scales again.' Documentation: https://learn.microsoft.com/en-us/azure/azure-monitor/autoscale/autoscale-understanding-settings#autoscale-evaluation

upvoted 2 times

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GarrethM

4 months ago

Selected Answer: D

First Scale-Out: After 15 minutes, the memory usage (80%) exceeds the 70% threshold, and the duration requirement is met. One instance is added, bringing the total to 3 instances. Cooldown Period: There's a 5-minute cooldown period after the first scale-out. Second Scale-Out: After the cooldown period (20 minutes total), the memory usage is still 80%, and another 15-minute duration has been met. One instance is added, bringing the total to 4 instances. Third Scale-Out: Again the cooldown period is met, and the 15 minute duration has been met. One instance is added, bringing the total to 5 instances. Since the maximum instances are set to 5, the autoscale will stop adding instances. Therefore, the maximum number of instances for App1 during the 30-minute period is 5.

upvoted 2 times

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vrm1358

4 months ago

Selected Answer: D

Tested in the lab. Cooldown period is set to 5 minutes. It means that after every scaling action, it waits for 5 mins to avoid infrequent changes unnecessarily. after 5 minutes (cooldown period), it looks back to last 15-minutes window of CPU utilization. As in the question, it has remained high, it initiates another scale-out action. In this scenario, scale-out keeps happening every 5 minutes until it reaches the max number of instance; ie 5.

upvoted 1 times

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Thor0007

6 months, 1 week ago

Selected Answer: D

The correct answer is D . Here you have to see the what is the definition of "Cool down" as per MS "The amount of time to wait before the rule is applied again so that the auto scale actions have time to take effect." So it will not wait for duration of 15 min again . That's logical . If anyone has any other ref official to MS share it in reply. Do upvote this for other help. Ref : https://learn.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-autoscale-portal

upvoted 1 times

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RajeshwaranM

6 months, 1 week ago

Selected Answer: B

In Azure's autoscale feature, when a scale-out rule is triggered—such as when CPU usage exceeds a specified threshold—the number of instances added is determined by the "instance count" specified in the autoscale rule, not by the duration for which the condition is met. So we have set the instance count 1 during the cool down period It will not scale our or scale in

upvoted 1 times

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Elsayed2030

6 months, 4 weeks ago

Selected Answer: B

Instances are NOT created during cool down period + 15 mins (as configured). Thus, after 15 mins you have +1 instance running and then nothing changes till another 20 mins

upvoted 2 times

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monisshk

7 months ago

Selected Answer: D

Correct Answer is D (5) Duration: - 15 minutes and Cooling Period: - 5 minutes 0-15 mins - 1+1 = 2 15 - 20 mins - 2+1 = 3 20 - 25 mins - 3+1 = 4 25 - 20 mins - 4+1 = 5

upvoted 3 times

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sca88

7 months, 4 weeks ago

Selected Answer: B

Should be B. 15 minutes with CPU > 70%, will scale out of 1. 5 minutes of cooldown => anything happen. start count other 15 minutes before scale out again... but the question talk about 30 minutes, so only 1 instance will be added. Total instance after 30 minutes = 3

upvoted 2 times

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Josh219

8 months ago

Selected Answer: B

Scale Out Event 1 (Immediate Trigger): Autoscale detects high memory usage. Initiates scaling to 3 instances. Instance Increase Time: 15 minutes. Time 15 Minutes: 3rd instance is up and running. Cool Down Period: Begins (5 minutes). Time 20 Minutes: Cool Down Period ends. If memory usage still at 80%, triggers scaling to 4 instances. Instance Increase Time: 15 minutes. Time 35 Minutes: 4th instance would be up and running. However, this is beyond the 30-minute window we are considering only 3

upvoted 3 times

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Karley7

8 months, 2 weeks ago

People who think the answer to this question is D, what do you think the answer to the next question is? https://www.examtopics.com/discussions/microsoft/view/67544-exam-az-104-topic-4-question-65-discussion/

upvoted 1 times

Josh219

8 months ago

its Box1: 3 Box2: 1

upvoted 1 times

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0378d43

8 months, 3 weeks ago

Selected Answer: B

15 mins 1 and then 5 mins cool and then remains 10 mins which does suffice the condition to scale out hence 2+1 =3

upvoted 2 times

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Stunomatic

8 months, 3 weeks ago

After every 5 min cool down it check most recent 15 minutes status that is why answer is 5 Summary of Scaling Actions in 30 Minutes 15-Minute Mark: Scales up to 3 instances. 20-Minute Mark: Scales up to 4 instances. 25-Minute Mark: Scales up to 5 instances (maximum limit reached).

upvoted 2 times

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magellan2050

8 months, 4 weeks ago

Selected Answer: C

Cooldown period only pauses the scaling operations but doesn't stop the metrics collection. Therefore we start with 2, after 15m +1. 3 consecutive cooldowns, no scaling but the metrics get collected, 15m +1 =4

upvoted 1 times

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