Proxy cache path configuration in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of proxy_cache_path directive with specific keys_zone

What is the effect of the following nginx configuration snippet on the cache zone named 'my_cache'?

Nginx

proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=my_cache:10m max_size=1g inactive=60m use_temp_path=off;

A Creates a cache zone 'my_cache' with 1GB shared memory, stores cache files in /data/nginx/cache with 10 level subdirectories, max size 10MB, inactive cache expires after 60 seconds, and enables temp path usage.

B Creates a cache zone 'my_cache' with 10MB shared memory, stores cache files in /data/nginx/cache with 1 and 2 level subdirectories, max size 1GB, inactive cache expires after 60 seconds, and disables temp path usage.

C Creates a cache zone 'my_cache' with 10MB shared memory, stores cache files in /data/nginx/cache with 1 and 2 level subdirectories, max size 1GB, inactive cache expires after 60 minutes, and disables temp path usage.

D Creates a cache zone 'my_cache' with 10MB shared memory, stores cache files in /data/nginx/cache with 2 and 1 level subdirectories, max size 1GB, inactive cache expires after 60 minutes, and enables temp path usage.

💡 Hint

Focus on the meaning of each parameter: keys_zone size, levels, max_size, inactive, and use_temp_path.

The keys_zone parameter defines the shared memory size for cache keys. Levels define the directory structure for cache files. Max_size limits total cache size. Inactive defines how long cached items stay without access before removal. Use_temp_path=off disables temporary file usage during caching.

🧠 Conceptual

intermediate

Understanding cache directory levels in proxy_cache_path

Why does nginx use multiple levels of directories (e.g., levels=1:2) in the proxy_cache_path configuration?

A To enable nginx to store cache files on multiple disks automatically.

B To increase cache size by creating nested directories that multiply storage capacity.

C To encrypt cache files by storing them in multiple directory levels for security.

D To distribute cache files into subdirectories to avoid too many files in a single directory, improving filesystem performance.

💡 Hint

Think about how filesystems handle many files in one folder.

Filesystems slow down when too many files are in one directory. Using multiple directory levels spreads files out, making access faster and more efficient.

❓ Troubleshoot

advanced

Troubleshooting cache not storing files

Given this proxy_cache_path configuration: proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=cache_zone:20m max_size=500m inactive=30m; And this proxy_cache usage: proxy_cache cache_zone; Why might nginx not store any cache files in /var/cache/nginx?

A The directory /var/cache/nginx does not have write permissions for the nginx worker process user.

B The keys_zone size of 20m is too small to store any cache files.

C The max_size of 500m is too large and prevents caching.

D The inactive time of 30m causes immediate cache expiration.

💡 Hint

Check file system permissions for the cache directory.

If nginx cannot write to the cache directory due to permission issues, it will not store cache files. The keys_zone size and max_size do not prevent caching by themselves. Inactive time controls expiration but does not stop caching initially.

✅ Best Practice

advanced

Best practice for proxy_cache_path keys_zone size

What is the recommended approach when setting the keys_zone size in proxy_cache_path for a high-traffic nginx server?

A Set keys_zone size large enough to hold all active cache keys in shared memory to avoid disk lookups.

B Set keys_zone size as small as possible to save memory, relying on disk for cache keys.

C Set keys_zone size equal to max_size to balance memory and disk usage.

D Set keys_zone size to zero to disable shared memory caching.

💡 Hint

Think about how nginx uses shared memory for cache keys.

A larger keys_zone allows nginx to keep more cache keys in fast shared memory, reducing disk access and improving performance. Too small keys_zone causes frequent disk lookups, slowing caching.

🔀 Workflow

expert

Correct order to enable proxy caching with custom cache path

Arrange the steps in the correct order to enable proxy caching in nginx with a custom cache directory '/custom/cache' and cache zone 'custom_zone'.

A 1,4,2,3

B 4,1,2,3

C 1,2,4,3

D 4,2,1,3

💡 Hint

Think about preparation before configuration and applying changes last.

First, create and set permissions on the cache directory (step 4). Then define proxy_cache_path (step 1). Next, enable proxy_cache in server/location block (step 2). Finally, reload nginx to apply changes (step 3).