Purging cached content in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to purge the cache for a specific URL using curl.

Nginx

curl -X [1] http://localhost/cache/purge/url

Drag options to blanks, or click blank then click option'

APURGE

BGET

CPOST

DDELETE

Attempts:

3 left

💡 Hint

Common Mistakes

Using GET or POST instead of PURGE will not remove cached content.

Using DELETE is not supported by nginx cache purging.

The PURGE method is used by nginx cache purging modules to remove cached content for a URL.

2fill in blank

medium

Complete the nginx configuration line to enable cache purging for the location '/cache/purge/'.

Nginx

location /cache/purge/ {
    [1] on;
}

Drag options to blanks, or click blank then click option'

Aproxy_cache_purge

Bproxy_cache

Cproxy_cache_path

Dproxy_cache_valid

Attempts:

3 left

💡 Hint

Common Mistakes

Using proxy_cache_path instead of proxy_cache_purge disables purging.

proxy_cache_valid controls cache duration, not purging.

The directive proxy_cache_purge on; enables purging cached content in the specified location.

3fill in blank

hard

Fix the error in this nginx cache purge location block by completing the missing directive.

Nginx

location /purge/ {
    allow 127.0.0.1;
    deny all;
    [1] on;
}

Drag options to blanks, or click blank then click option'

Aproxy_cache_key

Bproxy_cache_path

Cproxy_cache_purge

Dproxy_cache_methods

Attempts:

3 left

💡 Hint

Common Mistakes

Using proxy_cache_path or proxy_cache_key will cause errors or no purging.

Forgetting to allow local IPs will block purge requests.

The proxy_cache_purge on; directive is required to allow purging in this location block.

4fill in blank

hard

Fill both blanks to complete the nginx cache purge location that allows purging only from localhost and enables purging.

Nginx

location /cache/purge/ {
    [1] 127.0.0.1;
    [2] all;
    proxy_cache_purge on;
}

Drag options to blanks, or click blank then click option'

Aallow

Bdeny

Cproxy_cache

Dproxy_cache_path

Attempts:

3 left

💡 Hint

Common Mistakes

Reversing allow and deny directives.

Using proxy_cache directives instead of allow/deny.

The allow 127.0.0.1; permits localhost, and deny all; blocks others from purging.

5fill in blank

hard

Fill all three blanks to complete a dictionary comprehension that maps URLs to their cache purge commands.

Nginx

purge_commands = [1]: f"curl -X [2] http://localhost[3]" for [1] in urls if urls[[1]] == 'cache'

Drag options to blanks, or click blank then click option'

Aurl

BPURGE

DGET

Attempts:

3 left

💡 Hint

Common Mistakes

Using GET instead of PURGE will not purge cache.

Using different variable names inconsistently.

This comprehension creates commands for URLs marked as 'cache' using the PURGE method.

Practice

1. What is the main purpose of purging cached content in nginx?

easy

A. To remove specific cached files so fresh content is served

B. To increase the cache size automatically

C. To disable caching completely

D. To restart the nginx server

Solution

1. Step 1: Understand caching in nginx

   Caching stores copies of content to serve faster responses.

2. Step 2: Understand purging purpose

   Purging removes specific cached files to update content without restarting nginx.

3. Final Answer:

   To remove specific cached files so fresh content is served -> Option A

4. Quick Check:

   Purging = Remove cached files [OK]

Hint: Purging means deleting cached files to refresh content [OK]

Common Mistakes:

• Confusing purging with disabling cache
• Thinking purging restarts nginx
• Assuming purging increases cache size

2. Which of the following is the correct syntax to enable cache purging in an nginx location block?

easy

A. proxy_cache_purge true;

B. proxy_cache_purge off;

C. proxy_cache_purge enable;

D. proxy_cache_purge mycache;

Solution

1. Step 1: Recall nginx directive syntax

   Directives use the format: directive_name value; with zone name for cache purging.

2. Step 2: Identify correct value for enabling purge

   Enabling uses zone name 'mycache' not 'enable', 'true', or 'off'.

3. Final Answer:

   proxy_cache_purge mycache; -> Option D

4. Quick Check:

   Enable purge = proxy_cache_purge mycache; [OK]

Hint: Use the zone name to enable cache purging in nginx [OK]

Common Mistakes:

• Using 'enable' or 'true' instead of the zone name
• Forgetting the semicolon at the end
• Setting proxy_cache_purge to 'off' by mistake

3. Given this nginx config snippet:

location /purge/ {
    allow 192.168.1.0/24;
    deny all;
    proxy_cache_purge mycache;
}

What happens when a client from IP 192.168.1.10 sends a PURGE request to /purge/page1?

medium

A. The cached content for /purge/page1 is removed

B. The request is denied due to IP restriction

C. The cache is cleared for all pages

D. The server returns a 404 error

Solution

1. Step 1: Check IP access rules

   Allow 192.168.1.0/24 means IP 192.168.1.10 is allowed; others denied.

2. Step 2: Understand proxy_cache_purge mycache

   Enables purging cached content for matching requests.

3. Final Answer:

   The cached content for /purge/page1 is removed -> Option A

4. Quick Check:

   Allowed IP + PURGE request = cache removed [OK]

Hint: Allowed IP + PURGE request = cache cleared for that URL [OK]

Common Mistakes:

• Assuming all IPs can purge
• Thinking PURGE clears entire cache
• Confusing PURGE with GET request

4. You configured nginx to purge cache with:

location /purge/ {
    deny all;
    proxy_cache_purge mycache;
}

But PURGE requests still return 403 Forbidden. What is the likely cause?

medium

A. Cache is empty so purge fails

B. proxy_cache_purge directive is misspelled

C. Missing allow/deny rules to permit purge requests

D. PURGE method is not supported by nginx

Solution

1. Step 1: Understand default access control

   Without 'allow', nginx denies all due to 'deny all;' for security.

2. Step 2: Check purge access rules

   To allow PURGE requests, you must explicitly allow trusted IPs.

3. Final Answer:

   Missing allow/deny rules to permit purge requests -> Option C

4. Quick Check:

   deny all without allow = 403 Forbidden on PURGE [OK]

Hint: Always add allow/deny for purge locations [OK]

Common Mistakes:

• Assuming PURGE method is unsupported
• Ignoring access control rules
• Thinking empty cache causes 403

5. You want to purge cached content only for URLs starting with /images/ and restrict purge access to IP 10.0.0.5. Which nginx config snippet correctly achieves this?

hard

A. location /images/ {
proxy_cache_purge mycache;
allow 10.0.0.5;
deny all;
}

B. location /purge/images/ {
proxy_cache_purge mycache;
allow 10.0.0.5;
deny all;
}

C. location /images/ {
proxy_cache mycache;
allow 10.0.0.5;
deny all;
}

D. location /purge/ {
proxy_cache_purge mycache;
allow all;
}

Solution

1. Step 1: Identify purge location for /images/ URLs

   Purging usually uses a separate location like /purge/images/ to trigger cache removal.

2. Step 2: Check access control and purge directive

   Allow only IP 10.0.0.5 and deny others with proxy_cache_purge mycache enabled.

3. Final Answer:

   location /purge/images/ { proxy_cache_purge mycache; allow 10.0.0.5; deny all; } -> Option B

4. Quick Check:

   Correct purge path + access control = location /purge/images/ { proxy_cache_purge mycache; allow 10.0.0.5; deny all; } [OK]

Hint: Use a purge-specific location with allow/deny for security [OK]

Common Mistakes:

• Enabling purge in wrong location
• Using proxy_cache instead of proxy_cache_purge
• Allowing all IPs to purge