Minimum, maximum, and desired capacity in AWS - Mini Project: Build & Apply

Minimum, maximum, and desired capacity

📖 Scenario: You are managing a cloud application that needs to automatically adjust the number of servers running based on demand. To do this, you will set up an Auto Scaling Group with specific minimum, maximum, and desired capacity values.

🎯 Goal: Create an AWS Auto Scaling Group configuration that defines the minimum number of instances as 2, the maximum number of instances as 5, and the desired capacity as 3.

📋 What You'll Learn

Create a dictionary called asg_config to hold the Auto Scaling Group settings.

Add keys MinSize, MaxSize, and DesiredCapacity with the exact values 2, 5, and 3 respectively.

Use the exact key names and values as specified.

Ensure the configuration is valid for AWS Auto Scaling Group settings.

💡 Why This Matters

🌍 Real World

Auto Scaling Groups automatically adjust the number of servers to handle changes in traffic, saving costs and improving performance.

💼 Career

Understanding how to configure minimum, maximum, and desired capacity is essential for cloud engineers managing scalable applications.

1

Create the initial Auto Scaling Group configuration dictionary

Create a dictionary called asg_config with the keys MinSize, MaxSize, and DesiredCapacity set to 0 initially.

AWS

# Create the asg_config dictionary with MinSize, MaxSize, and DesiredCapacity set to 0
# Your code here

Hint

Use curly braces to create a dictionary and set each key to 0.

2

Add the minimum capacity value

Update the asg_config dictionary to set the MinSize key to the integer value 2.

AWS

asg_config = {
    'MinSize': 0,
    'MaxSize': 0,
    'DesiredCapacity': 0
}
# Set MinSize to 2 below
# Your code here

Hint

Change the value for the key 'MinSize' to 2.

3

Add the maximum capacity value

Update the asg_config dictionary to set the MaxSize key to the integer value 5.

AWS

asg_config = {
    'MinSize': 2,
    'MaxSize': 0,
    'DesiredCapacity': 0
}
# Set MaxSize to 5 below
# Your code here

Hint

Change the value for the key 'MaxSize' to 5.

4

Add the desired capacity value

Update the asg_config dictionary to set the DesiredCapacity key to the integer value 3.

AWS

asg_config = {
    'MinSize': 2,
    'MaxSize': 5,
    'DesiredCapacity': 0
}
# Set DesiredCapacity to 3 below
# Your code here

Hint

Change the value for the key 'DesiredCapacity' to 3.

Practice

1. What does the MinSize setting control in an AWS Auto Scaling group?

easy

A. The exact number of servers to run at all times

B. The largest number of servers allowed to run

C. The smallest number of servers that must always be running

D. The number of servers to add during scaling

Solution

1. Step 1: Understand MinSize meaning

   MinSize defines the minimum number of servers that the Auto Scaling group keeps running to handle load.

2. Step 2: Compare with other settings

   MaxSize is the maximum allowed, DesiredCapacity is the target number, so MinSize is the smallest number always running.

3. Final Answer:

   The smallest number of servers that must always be running -> Option C

4. Quick Check:

   MinSize = smallest server count [OK]

Hint: MinSize = minimum servers always running [OK]

Common Mistakes:

• Confusing MinSize with DesiredCapacity
• Thinking MinSize is maximum limit
• Assuming MinSize is the exact number to run

2. Which of the following is the correct way to set the desired capacity to 5 in an AWS Auto Scaling group configuration snippet?

easy

A. DesiredCapacity => 5

B. "DesiredCapacity" = 5

C. DesiredCapacity: "5"

D. "DesiredCapacity": 5

Solution

1. Step 1: Identify correct JSON syntax

   In JSON, keys and string values use double quotes and key-value pairs use colon (:).

2. Step 2: Check each option

   "DesiredCapacity": 5 uses correct JSON syntax: key in quotes, colon, numeric value without quotes.

3. Final Answer:

   "DesiredCapacity": 5 -> Option D

4. Quick Check:

   JSON key-value uses colon and quotes [OK]

Hint: JSON uses colon and quotes for keys [OK]

Common Mistakes:

• Using equals sign instead of colon
• Putting numbers in quotes unnecessarily
• Using arrow symbols instead of colon

3. Given an Auto Scaling group with MinSize=2, MaxSize=6, and DesiredCapacity=4, what happens if the current number of running servers is 5 and one server fails?

medium

A. The group does nothing because the current number of running servers equals DesiredCapacity

B. The group launches a new server to maintain DesiredCapacity of 4

C. The group terminates another server to reach DesiredCapacity

D. The group launches two new servers to reach MaxSize

Solution

1. Step 1: Understand DesiredCapacity role

   DesiredCapacity is the target number of servers to keep running, here 4.

2. Step 2: Analyze failure impact

   One server fails, so running servers drop from 5 to 4, which matches DesiredCapacity.

3. Step 3: Check if scaling needed

   Since running servers dropped below DesiredCapacity, the group launches a new server to maintain DesiredCapacity.

4. Final Answer:

   The group launches a new server to maintain DesiredCapacity of 4 -> Option B

5. Quick Check:

   Running servers < DesiredCapacity triggers scaling [OK]

Hint: Scaling triggers only if running servers < DesiredCapacity [OK]

Common Mistakes:

• Assuming scaling happens immediately on failure
• Confusing MinSize with DesiredCapacity
• Thinking MaxSize limits minimum servers

4. You configured an Auto Scaling group with MinSize=3, MaxSize=5, and DesiredCapacity=6. What is the problem?

medium

A. DesiredCapacity cannot be greater than MaxSize

B. MinSize cannot be less than DesiredCapacity

C. MaxSize cannot be less than MinSize

D. No problem, this configuration is valid

Solution

1. Step 1: Check relationship between capacities

   DesiredCapacity must be between MinSize and MaxSize inclusive.

2. Step 2: Compare values

   DesiredCapacity is 6, but MaxSize is 5, which is less than DesiredCapacity.

3. Step 3: Identify error

   This violates the rule that DesiredCapacity cannot exceed MaxSize.

4. Final Answer:

   DesiredCapacity cannot be greater than MaxSize -> Option A

5. Quick Check:

   DesiredCapacity ≤ MaxSize [OK]

Hint: DesiredCapacity must be ≤ MaxSize [OK]

Common Mistakes:

• Setting DesiredCapacity higher than MaxSize
• Confusing MinSize and MaxSize roles
• Assuming any values are allowed

5. You want an Auto Scaling group to always run at least 2 servers, never more than 8, and normally keep 5 running. If traffic suddenly spikes, which setting controls the maximum servers it can scale up to, and what should it be set to?

hard

A. MaxSize controls maximum servers; set to 8

B. DesiredCapacity controls maximum servers; set to 8

C. MinSize controls maximum servers; set to 5

D. DesiredCapacity controls maximum servers; set to 2

Solution

1. Step 1: Identify which setting limits maximum servers

   MaxSize sets the upper limit of servers allowed in the group.

2. Step 2: Match requirement to setting

   To never exceed 8 servers, MaxSize must be set to 8.

3. Step 3: Understand DesiredCapacity and MinSize roles

   DesiredCapacity is the target number (5), MinSize is the minimum (2), neither limits maximum scaling.

4. Final Answer:

   MaxSize controls maximum servers; set to 8 -> Option A

5. Quick Check:

   MaxSize = max servers allowed [OK]

Hint: MaxSize limits max servers; DesiredCapacity is target [OK]

Common Mistakes:

• Confusing DesiredCapacity with MaxSize
• Setting MinSize as maximum limit
• Not setting MaxSize high enough for spikes