Purging CDN cache in Azure - Commands & Configuration

Introduction

Sometimes, when you update your website or app content, the old version still shows because it is saved in the CDN cache. Purging the CDN cache removes these old files so visitors see the newest content right away.

When you update images or files on your website and want users to see the changes immediately.

When you fix a bug in your web content and need to remove the cached broken version.

When you deploy a new version of your app and want to clear old cached files to avoid confusion.

When you want to test changes and need to make sure the CDN is not serving outdated content.

When you notice your users are seeing stale content due to caching delays.

Commands

This command clears all cached content from the specified CDN endpoint so that users will get fresh content on their next request.

Terminal

az cdn endpoint purge --resource-group example-resource-group --profile-name example-cdn-profile --name example-endpoint --content-paths '/*'

Expected Output

Starting purge operation...

Purge operation completed successfully.

→

--resource-group - Specifies the Azure resource group where the CDN profile is located.

→

--profile-name - Specifies the name of the CDN profile that contains the endpoint.

→

--content-paths - Specifies which cached paths to purge; '/*' means all cached content.

This command checks the status of the CDN endpoint to confirm it is active and ready after the purge.

Terminal

az cdn endpoint show --resource-group example-resource-group --profile-name example-cdn-profile --name example-endpoint

Expected Output

{

  "id": "/subscriptions/xxxx/resourceGroups/example-resource-group/providers/Microsoft.Cdn/profiles/example-cdn-profile/endpoints/example-endpoint",

  "name": "example-endpoint",

  "resourceGroup": "example-resource-group",

  "status": "Running",

  "type": "Microsoft.Cdn/profiles/endpoints"

}

→

--resource-group - Specifies the resource group of the CDN profile.

→

--profile-name - Specifies the CDN profile name.

Key Concept

If you remember nothing else from this pattern, remember: purging the CDN cache forces the CDN to fetch fresh content from your origin server immediately.

Common Mistakes

Not specifying the correct resource group or profile name in the purge command.

The command will fail or purge the wrong CDN endpoint, leaving your content stale.

Always double-check the resource group and profile name to target the correct CDN endpoint.

Using incorrect content paths or forgetting to include '/*' to purge all content.

Only partial or no cached content will be purged, so users may still see old files.

Use '/*' to purge all cached content or specify exact paths you want to clear.

Summary

Use 'az cdn endpoint purge' with the right resource group, profile, and endpoint to clear cached content.

Use 'az cdn endpoint show' to verify the CDN endpoint status after purging.

Purging forces the CDN to serve fresh content from your origin server immediately.

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