FastCGI cache in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable FastCGI cache in nginx configuration.

Nginx

fastcgi_cache_path /var/cache/nginx levels=1:2 keys_zone=my_cache:10m [1] inactive=60m;

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

Amax_size=1g

Bmax_size=100m

Cmax_size=10g

Dmax_size=500m

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the max_size directive causes unlimited cache size.

Using too large cache size without enough disk space.

The max_size directive sets the maximum size of the cache. 100m is a common safe default.

2fill in blank

medium

Complete the code to set the cache key for FastCGI cache.

Nginx

fastcgi_cache_key [1];

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

A$scheme$host$request_uri

B$scheme$request_method$host$request_uri$request_body

C$scheme$request_method$host$request_uri

D$host$request_uri

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving out request method can cause cache collisions.

Including request body in cache key is not typical.

The cache key should uniquely identify the request. Using scheme, method, host, and URI is common.

3fill in blank

hard

Fix the error in the FastCGI cache configuration to enable caching in the location block.

Nginx

location ~ \.php$ {
    fastcgi_pass unix:/run/php/php7.4-fpm.sock;
    fastcgi_cache [1];
    include fastcgi_params;
}

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

Amy_cache

Bcache_zone

Cfast_cache

Dcache

Attempts:

3 left

💡 Hint

Common Mistakes

Using an undefined cache zone name causes nginx to fail.

Misspelling the cache zone name.

The fastcgi_cache directive must reference the name of the cache zone defined by keys_zone, here my_cache.

4fill in blank

hard

Fill both blanks to set cache validity times for different response codes.

Nginx

fastcgi_cache_valid 200 [1];
fastcgi_cache_valid 404 [2];

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

A10m

B1m

C5m

D30s

Attempts:

3 left

💡 Hint

Common Mistakes

Caching 404 errors for too long can cause stale error pages.

Using invalid time units causes nginx errors.

Successful responses (200) are cached longer (10 minutes), while 404 errors are cached shorter (1 minute).

5fill in blank

hard

Fill all three blanks to configure cache bypass and cache use conditions.

Nginx

fastcgi_cache_bypass [1];
fastcgi_no_cache [2];
fastcgi_cache_use_stale [3];

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

A$http_cache_control

B$cookie_nocache

Cerror timeout invalid_header http_500

D$request_method

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up variables for bypass and no_cache.

Not specifying error types for stale cache use.

fastcgi_cache_bypass disables cache if $cookie_nocache is set.
fastcgi_no_cache disables cache if $http_cache_control header is present.
fastcgi_cache_use_stale allows serving stale cache on errors like 500 or timeout.

Practice

1. What is the main purpose of enabling FastCGI cache in nginx?

easy

A. To store dynamic page responses and serve them faster next time

B. To block all dynamic content from being served

C. To increase the size of the nginx log files

D. To disable backend server processing completely

Solution

1. Step 1: Understand FastCGI cache function

   FastCGI cache stores dynamic content generated by backend servers temporarily.

2. Step 2: Identify the benefit

   Serving cached content reduces backend load and speeds up response time.

3. Final Answer:

   To store dynamic page responses and serve them faster next time -> Option A

4. Quick Check:

   FastCGI cache purpose = store and speed up [OK]

Hint: FastCGI cache speeds up dynamic pages by storing them [OK]

Common Mistakes:

• Thinking it blocks dynamic content
• Confusing cache with logging
• Assuming it disables backend servers

2. Which of the following is the correct syntax to define a FastCGI cache zone in nginx?

easy

A. fastcgi_cache /path/to/cache keys_zone=mycache inactive=60m;

B. fastcgi_cache_zone /path/to/cache keys_zone=mycache:10m inactive=60m;

C. fastcgi_cache_path keys_zone=mycache:10m /path/to/cache inactive=60m;

D. fastcgi_cache_path /path/to/cache levels=1:2 keys_zone=mycache:10m inactive=60m;

Solution

1. Step 1: Recall fastcgi_cache_path syntax

   The correct syntax includes path, levels, keys_zone with size, and inactive time.

2. Step 2: Match options with syntax

   fastcgi_cache_path /path/to/cache levels=1:2 keys_zone=mycache:10m inactive=60m; matches the correct order and parameters exactly.

3. Final Answer:

   fastcgi_cache_path /path/to/cache levels=1:2 keys_zone=mycache:10m inactive=60m; -> Option D

4. Quick Check:

   Correct fastcgi_cache_path syntax = fastcgi_cache_path /path/to/cache levels=1:2 keys_zone=mycache:10m inactive=60m; [OK]

Hint: Remember: fastcgi_cache_path needs path, levels, keys_zone [OK]

Common Mistakes:

• Mixing keys_zone and path order
• Omitting levels parameter
• Using fastcgi_cache instead of fastcgi_cache_path

3. Given this nginx config snippet:

fastcgi_cache_path /var/cache/nginx levels=1:2 keys_zone=cache_zone:10m inactive=30m;
server {
  location ~ \.php$ {
    fastcgi_cache cache_zone;
    fastcgi_cache_valid 200 10m;
    fastcgi_pass backend;
  }
}

What happens when a PHP page is requested twice within 10 minutes?

medium

A. The cache is cleared after the first request

B. Both requests are forwarded to the backend server

C. The second request is served from cache, speeding up response

D. The second request returns a 404 error

Solution

1. Step 1: Understand fastcgi_cache_valid 200 10m

   This means HTTP 200 responses are cached for 10 minutes.

2. Step 2: Analyze repeated request behavior

   The first request caches the response; the second request within 10 minutes uses cache.

3. Final Answer:

   The second request is served from cache, speeding up response -> Option C

4. Quick Check:

   Cache valid time means reuse cached response [OK]

Hint: fastcgi_cache_valid sets cache duration for status codes [OK]

Common Mistakes:

• Assuming backend always handles requests
• Thinking cache clears after first request
• Confusing cache duration with cache clearing

4. You configured FastCGI cache but notice no caching happens. Which nginx directive is most likely missing?

medium

A. fastcgi_cache_path

B. fastcgi_cache_key

C. fastcgi_cache_valid

D. fastcgi_pass

Solution

1. Step 1: Identify required directives for caching

   fastcgi_cache_path defines cache storage; fastcgi_cache_valid sets cache time; fastcgi_pass sends requests to backend.

2. Step 2: Understand fastcgi_cache_key role

   fastcgi_cache_key defines how requests are identified for caching; missing it disables caching.

3. Final Answer:

   fastcgi_cache_key -> Option B

4. Quick Check:

   Missing cache key disables caching [OK]

Hint: Without fastcgi_cache_key, nginx can't store cache properly [OK]

Common Mistakes:

• Forgetting to set fastcgi_cache_key
• Confusing fastcgi_cache_valid with cache enabling
• Assuming fastcgi_pass controls caching

5. You want to cache PHP responses but exclude logged-in users identified by a cookie user_session. Which configuration snippet correctly disables cache for logged-in users?

hard

A. fastcgi_no_cache $cookie_user_session;

B. fastcgi_cache_valid 200 10m if_not $cookie_user_session;

C. fastcgi_cache_key $cookie_user_session;

D. fastcgi_cache_bypass $cookie_user_session;

Solution

1. Step 1: Understand directives controlling cache bypass

   fastcgi_no_cache disables caching when its variable is true; fastcgi_cache_bypass skips cache lookup but may still cache response.

2. Step 2: Identify correct directive for excluding logged-in users

   fastcgi_no_cache $cookie_user_session; disables caching for requests with that cookie, preventing cached content for logged-in users.

3. Final Answer:

   fastcgi_no_cache $cookie_user_session; -> Option A

4. Quick Check:

   fastcgi_no_cache disables caching for matching requests [OK]

Hint: Use fastcgi_no_cache to exclude requests from caching [OK]

Common Mistakes:

• Using fastcgi_cache_bypass alone to prevent caching
• Trying to conditionally set fastcgi_cache_valid
• Misusing fastcgi_cache_key for cache control