Purging CDN cache in Azure - Step-by-Step Execution

Process Flow - Purging CDN cache

Request to purge cache

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Authenticate request

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Identify CDN endpoint

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Send purge command

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CDN invalidates cached content

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Confirm purge success

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Serve fresh content on next request

The purge process starts with a request, authenticates it, targets the CDN endpoint, sends the purge command, invalidates cached content, confirms success, and then serves fresh content.

Execution Sample

Azure

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

This command purges cached content under '/images/*' from the specified Azure CDN endpoint.

Process Table

Step	Action	Input/Parameter	System Response	Result
1	Receive purge request	ResourceGroup=MyResourceGroup, Profile=MyProfile, Endpoint=MyEndpoint, Paths='/images/*'	Request accepted	Proceed to authentication
2	Authenticate request	User credentials or token	Authentication successful	Proceed to identify endpoint
3	Identify CDN endpoint	MyEndpoint under MyProfile	Endpoint found	Ready to send purge command
4	Send purge command	Paths='/images/*'	Purge command sent to CDN	Cache invalidation started
5	CDN invalidates cache	Paths='/images/*'	Cache entries removed	Content will be refreshed on next request
6	Confirm purge success	System status	Purge completed successfully	End process
7	Serve fresh content	Next user request	Fetches fresh content from origin	User receives updated content

💡 Purge completes after cache invalidation and confirmation, ensuring fresh content delivery.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	Final
Request Status	None	Received	Authenticated	Endpoint Identified	Purge Command Sent	Cache Invalidated	Purge Confirmed	Completed
Cache State	Cached content present	Cached content present	Cached content present	Cached content present	Invalidation in progress	Cache cleared for '/images/*'	Cache cleared	Fresh content served

Key Moments - 3 Insights

Why does the purge command target specific content paths like '/images/*' instead of the whole cache?

Targeting specific paths limits the purge scope, making it faster and less disruptive. See execution_table row 4 where the purge command is sent only for '/images/*'.

What happens if authentication fails during the purge request?

The process stops at step 2 in the execution_table because the request is not authorized, so no cache invalidation occurs.

Does purging immediately update content for all users?

No, purging invalidates cached content so that on the next user request (step 7), fresh content is fetched from the origin server.

Visual Quiz - 3 Questions

Look at the execution_table, what is the system response at step 3?

A Authentication successful

B Endpoint found

C Purge command sent to CDN

D Cache entries removed

💡 Hint

Check the 'System Response' column for step 3 in the execution_table.

At which step does the cache actually get cleared for the specified paths?

A Step 4

B Step 5

C Step 6

D Step 7

💡 Hint

Look for 'Cache entries removed' in the 'System Response' column.

If the purge command targeted the whole cache instead of '/images/*', how would the variable 'Cache State' change after step 5?

A Only '/images/*' cache cleared

B No change in cache state

C Entire cache cleared

D Cache state becomes invalid

💡 Hint

Refer to variable_tracker row 'Cache State' after step 5 and imagine the scope change.

Concept Snapshot

Purging CDN cache removes outdated content from the CDN.
Use Azure CLI command 'az cdn endpoint purge' with resource group, profile, endpoint, and content paths.
Authentication is required before purging.
Only specified paths are purged to limit impact.
After purge, fresh content is served on next request.

Full Transcript

Purging CDN cache in Azure involves sending a purge request specifying the resource group, CDN profile, endpoint, and content paths to clear. The system authenticates the request, identifies the CDN endpoint, and sends the purge command. The CDN then invalidates the cached content for the specified paths. Once the purge is confirmed, the next user request fetches fresh content from the origin server. This process ensures users receive updated content without waiting for cache expiration.