Purging CDN cache in Azure - Mini Project: Build & Apply

Purging CDN Cache in Azure

📖 Scenario: You manage a website hosted on Azure and use Azure CDN to deliver content quickly to users worldwide. Sometimes, you update your website content and need to clear the cached files on the CDN so visitors see the latest version immediately.

🎯 Goal: Build a simple Azure CLI script that purges the CDN cache for specific paths, ensuring the latest content is served to users.

📋 What You'll Learn

Create a variable with the Azure CDN profile name

Create a variable with the Azure CDN endpoint name

Create a list variable with the paths to purge

Write the Azure CLI command to purge the CDN cache using the variables

💡 Why This Matters

🌍 Real World

Websites and apps use CDNs to speed up content delivery. When content changes, purging the CDN cache ensures users see the latest version quickly.

💼 Career

Cloud engineers and DevOps professionals often automate CDN cache purging to maintain content freshness without manual steps.

1

Set Azure CDN profile name

Create a variable called cdn_profile and set it to the exact string myCdnProfile.

Azure

# Create a variable called cdn_profile and set it to 'myCdnProfile'
# Your code here

Hint

The CDN profile name is the name of your Azure CDN profile.

2

Set Azure CDN endpoint name

Create a variable called cdn_endpoint and set it to the exact string myCdnEndpoint.

Azure

cdn_profile = 'myCdnProfile'
# Create a variable called cdn_endpoint and set it to 'myCdnEndpoint'
# Your code here

Hint

The CDN endpoint is the specific endpoint under your CDN profile.

3

Define paths to purge

Create a list variable called paths_to_purge with these exact strings: "/images/*" and "/css/*".

Azure

cdn_profile = 'myCdnProfile'
cdn_endpoint = 'myCdnEndpoint'
# Create a list called paths_to_purge with '/images/*' and '/css/*'
# Your code here

Hint

Paths specify which cached files to clear on the CDN.

4

Write Azure CLI purge command

Write a string variable called purge_command that contains the exact Azure CLI command to purge the CDN cache using cdn_profile, cdn_endpoint, and paths_to_purge. The command should be: az cdn endpoint purge --profile-name {cdn_profile} --name {cdn_endpoint} --resource-group myResourceGroup --content-paths {paths_to_purge} where {paths_to_purge} is a space-separated string of the paths.

Azure

cdn_profile = 'myCdnProfile'
cdn_endpoint = 'myCdnEndpoint'
paths_to_purge = ['/images/*', '/css/*']
# Create a string variable purge_command with the Azure CLI purge command
# Your code here

Hint

Use an f-string to insert variables and join the paths with spaces.

Practice

1. What is the main purpose of purging a CDN cache in Azure?

easy

A. To increase the storage capacity of the CDN

B. To remove outdated content so users get the latest version

C. To add new content to the CDN cache

D. To monitor traffic statistics on the CDN

Solution

1. Step 1: Understand CDN cache role

   CDN caches store copies of content to serve users faster.

2. Step 2: Purpose of purging cache

   Purging removes old cached content so fresh content is served.

3. Final Answer:

   To remove outdated content so users get the latest version -> Option B

4. Quick Check:

   Purging = Remove outdated content [OK]

Hint: Purging means clearing old cache to refresh content [OK]

Common Mistakes:

• Thinking purging adds content instead of removing
• Confusing purging with monitoring or scaling
• Believing purging increases storage capacity

2. Which Azure CLI command correctly purges the CDN cache for a specific content path?

easy

A. az cdn endpoint purge --resource-group MyGroup --profile-name MyProfile --name MyEndpoint --content-paths '/images/*'

B. az cdn endpoint create --resource-group MyGroup --profile-name MyProfile --name MyEndpoint --content-paths '/images/*'

C. az cdn endpoint start --resource-group MyGroup --profile-name MyProfile --name MyEndpoint --content-paths '/images/*'

D. az cdn profile purge --resource-group MyGroup --name MyProfile --content-paths '/images/*'

Solution

1. Step 1: Identify correct command for purging

   The command to purge cache is az cdn endpoint purge.

2. Step 2: Check parameters

   It requires resource group, profile name, endpoint name, and content paths.

3. Final Answer:

   az cdn endpoint purge --resource-group MyGroup --profile-name MyProfile --name MyEndpoint --content-paths '/images/*' -> Option A

4. Quick Check:

   Purging uses az cdn endpoint purge [OK]

Hint: Purge command uses 'endpoint purge' with content paths [OK]

Common Mistakes:

• Using 'create' or 'start' commands instead of 'purge'
• Confusing profile purge with endpoint purge
• Omitting required parameters like endpoint name

3. Given this Azure CLI command:
az cdn endpoint purge --resource-group RG1 --profile-name Profile1 --name Endpoint1 --content-paths '/css/*' '/js/app.js'
What will happen after running it?

medium

A. The command will fail due to incorrect syntax

B. Only the '/css/*' files will be purged from the CDN cache

C. Both '/css/*' and '/js/app.js' files will be purged from the CDN cache

D. Only '/js/app.js' will be purged, '/css/*' will be ignored

Solution

1. Step 1: Analyze content-paths parameter

   The command lists two paths: '/css/*' and '/js/app.js'. Both are valid and separated by space.

2. Step 2: Understand purge effect

   Both specified paths will be purged from the CDN cache after command runs.

3. Final Answer:

   Both '/css/*' and '/js/app.js' files will be purged from the CDN cache -> Option C

4. Quick Check:

   Multiple paths purge all listed [OK]

Hint: Multiple content paths purge all specified files [OK]

Common Mistakes:

• Assuming only first path is purged
• Thinking command syntax is invalid with multiple paths
• Believing wildcard and file path cannot be combined

4. You run this command to purge CDN cache:
az cdn endpoint purge --resource-group RG1 --profile-name Profile1 --name Endpoint1 --content-paths '/images/logo.png'
But the cache is not cleared. What is the most likely cause?

medium

A. The content path is incorrect or does not match cached files

B. The resource group name is misspelled

C. The Azure CLI command does not support purging images

D. The CDN endpoint is not created yet

Solution

1. Step 1: Check command correctness

   The command syntax is correct and supports purging images.

2. Step 2: Identify common purge failure reason

   If cache is not cleared, often the content path does not match cached files exactly.

3. Final Answer:

   The content path is incorrect or does not match cached files -> Option A

4. Quick Check:

   Incorrect path = purge fails [OK]

Hint: Verify content path matches cached files exactly [OK]

Common Mistakes:

• Assuming CLI cannot purge images
• Ignoring typos in resource group or endpoint names
• Thinking purge works instantly without matching paths

5. You manage a global website using Azure CDN. You want to purge cache for a frequently updated JavaScript file but minimize performance impact. Which strategy is best?

hard

A. Disable CDN caching for all files to avoid purging

B. Purge the entire CDN endpoint cache every hour

C. Purge cache only once a month to reduce load

D. Purge only the specific JavaScript file path instead of the entire CDN endpoint

Solution

1. Step 1: Understand impact of purging scope

   Purging entire endpoint cache causes high load and delays for all users.

2. Step 2: Choose targeted purging

   Purging only the specific JavaScript file updates that content with minimal performance impact.

3. Final Answer:

   Purge only the specific JavaScript file path instead of the entire CDN endpoint -> Option D

4. Quick Check:

   Targeted purge = minimal impact [OK]

Hint: Purge specific files, not whole endpoint, to save performance [OK]

Common Mistakes:

• Purging entire cache too often causing slowdowns
• Disabling caching loses CDN benefits
• Purging too rarely causing stale content