Proxy cache path configuration in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the proxy_cache_path directive in nginx?

It defines the location on disk where nginx stores cached responses from proxied servers. This helps speed up repeated requests by serving cached content.

intermediate

Which parameters can you set in proxy_cache_path to control cache size and behavior?

You can set parameters like levels (directory structure), keys_zone (shared memory zone name and size), max_size (maximum cache size), inactive (time before cached items expire), and use_temp_path.

intermediate

Explain the role of the keys_zone parameter in proxy_cache_path.

It defines a shared memory zone that stores cache keys and metadata. This zone allows nginx worker processes to share cache information efficiently.

beginner

What does the levels parameter do in proxy_cache_path?

It sets the directory structure depth for storing cached files. For example, levels=1:2 creates a two-level folder hierarchy to avoid too many files in one directory.

beginner

How do you enable proxy caching for a location block after configuring proxy_cache_path?

Use the proxy_cache directive inside the location block with the name of the cache zone defined in keys_zone. For example, proxy_cache my_cache_zone;.

What does the max_size parameter in proxy_cache_path control?

A Maximum number of worker processes

B Maximum size of HTTP request body

C Maximum number of cached keys in memory

D Maximum size of the cache on disk

max_size limits how much disk space the cache can use.

Which parameter defines the shared memory zone for caching in nginx?

A proxy_cache_key

B keys_zone

C proxy_cache_path

D proxy_cache_valid

keys_zone is a parameter inside proxy_cache_path that defines the shared memory zone.

What is the effect of setting levels=1:2 in proxy_cache_path?

A Cache files are stored in a two-level directory structure

B Cache files are stored in a single directory

C Cache files are stored in three nested directories

D Cache files are stored in memory only

This creates a two-level folder hierarchy with 1-character named directories at the first level and 2-character named directories at the second level.

How do you activate caching for a specific location in nginx?

A Use <code>cache_enable</code> directive

B Use <code>proxy_cache_path</code> inside the location block

C Use <code>proxy_cache</code> directive with the cache zone name

D Use <code>cache_zone</code> directive

proxy_cache enables caching using the named cache zone.

What happens if the cache size exceeds the max_size limit?

A Old cached files are deleted to free space

B New cache files are rejected

C Nginx stops serving cached content

D Cache size automatically increases

Nginx removes old cache files to keep the cache size within the limit.

Describe how to configure proxy cache storage in nginx using proxy_cache_path. Include key parameters and their roles.

Think about where cache files go, how nginx organizes them, and how it limits cache size.

Explain the steps to enable proxy caching for a website location after setting up the cache path.

Focus on linking the cache storage setup with the location block configuration.

Practice

1. What is the main purpose of the proxy_cache_path directive in nginx?

easy

A. To set the maximum number of client connections

B. To specify the backend server IP address

C. To configure SSL certificates for secure connections

D. To define where and how cached files are stored

Solution

1. Step 1: Understand the role of proxy_cache_path

   The proxy_cache_path directive tells nginx where to save cached files and how to manage them.

2. Step 2: Compare with other options

   Options A, C, and D relate to connections, SSL, and backend servers, not caching.

3. Final Answer:

   To define where and how cached files are stored -> Option D

4. Quick Check:

   proxy_cache_path = cache storage location [OK]

Hint: proxy_cache_path sets cache storage location [OK]

Common Mistakes:

• Confusing proxy_cache_path with proxy_pass
• Thinking it sets connection limits
• Mixing it with SSL configuration

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

easy

A. proxy_cache_path /data/cache keys_zone=mycache:10m max_size=1g inactive=60m;

B. proxy_cache_path /data/cache keys_zone=mycache 10m max_size=1g inactive=60m

C. proxy_cache_path /data/cache keys_zone mycache:10m max_size=1g inactive=60m;

D. proxy_cache_path /data/cache keys_zone=mycache:10m max_size=1g inactive=60m

Solution

1. Step 1: Check syntax requirements for proxy_cache_path

   The directive requires a semicolon at the end and correct key-value pairs with colons where needed.

2. Step 2: Identify correct option

   proxy_cache_path /data/cache keys_zone=mycache:10m max_size=1g inactive=60m; has correct syntax with colon in keys_zone, key-value pairs, and ends with a semicolon.

3. Final Answer:

   proxy_cache_path /data/cache keys_zone=mycache:10m max_size=1g inactive=60m; -> Option A

4. Quick Check:

   Correct syntax ends with semicolon and uses colons properly [OK]

Hint: Always end proxy_cache_path with semicolon and use colons in keys_zone [OK]

Common Mistakes:

• Missing semicolon at the end
• Using space instead of colon in keys_zone
• Omitting equal signs in parameters

3. Given this nginx configuration snippet:

proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=mycache:10m max_size=500m inactive=30m;

What happens when a cached file is not accessed for 40 minutes?

medium

A. The cached file is refreshed automatically

B. The cached file remains because max_size is 500m

C. The cached file is removed because it is inactive longer than 30 minutes

D. The cached file is moved to a different cache zone

Solution

1. Step 1: Understand the inactive parameter

   The inactive=30m means cached files not accessed for 30 minutes are removed.

2. Step 2: Apply to 40 minutes inactivity

   Since 40 minutes > 30 minutes, the cached file will be removed.

3. Final Answer:

   The cached file is removed because it is inactive longer than 30 minutes -> Option C

4. Quick Check:

   inactive=30m means remove after 30 minutes inactivity [OK]

Hint: inactive time removes unused cache files after set duration [OK]

Common Mistakes:

• Confusing max_size with inactive time
• Assuming cache refresh happens automatically
• Thinking cache files move zones

4. You wrote this proxy cache path configuration:

proxy_cache_path /cache keys_zone=mycache 10m max_size=1g inactive=60m;

nginx fails to start. What is the error?

medium

A. Missing colon between keys_zone name and size

B. Invalid max_size value

C. Path /cache does not exist

D. inactive parameter should be in seconds

Solution

1. Step 1: Check keys_zone syntax

   The keys_zone requires a colon between the zone name and size, e.g., mycache:10m.

2. Step 2: Identify missing colon

   The config uses keys_zone=mycache 10m missing the colon, causing syntax error.

3. Final Answer:

   Missing colon between keys_zone name and size -> Option A

4. Quick Check:

   keys_zone syntax requires colon like mycache:10m [OK]

Hint: keys_zone must have colon between name and size [OK]

Common Mistakes:

• Forgetting colon in keys_zone
• Assuming inactive needs seconds
• Ignoring path existence errors

5. You want to configure nginx to cache responses in /var/cache/nginx with a 20MB keys zone, max cache size 2GB, and remove files inactive for 15 minutes. Which is the correct proxy_cache_path directive?

hard

A. proxy_cache_path /var/cache/nginx keys_zone=mycache:20m max_size=2gb inactive=15m;

B. proxy_cache_path /var/cache/nginx keys_zone=mycache:20m max_size=2g inactive=15m;

C. proxy_cache_path /var/cache/nginx keys_zone=mycache:20m max_size=1024m inactive=15m;

D. proxy_cache_path /var/cache/nginx keys_zone=mycache:20m max_size=2g inactive=900;

Solution

1. Step 1: Verify keys_zone size and path

   Keys zone size is 20m and path is /var/cache/nginx, both correct in all options.

2. Step 2: Check max_size and inactive syntax

   Max size should be 2g (gigabytes), inactive time 15m (minutes). proxy_cache_path /var/cache/nginx keys_zone=mycache:20m max_size=2g inactive=15m; uses correct units and syntax.

3. Step 3: Identify errors in other options

   proxy_cache_path /var/cache/nginx keys_zone=mycache:20m max_size=2gb inactive=15m; uses '2gb' (invalid unit), C uses 1024m (1GB not 2GB), D uses inactive=900 (seconds, but default is minutes and needs 's').

4. Final Answer:

   proxy_cache_path /var/cache/nginx keys_zone=mycache:20m max_size=2g inactive=15m; -> Option B

5. Quick Check:

   Use correct units: m for MB, g for GB, and time units with m for minutes [OK]

Hint: Use correct units: m for MB, g for GB, and m for minutes [OK]

Common Mistakes:

• Using invalid units like 'gb' instead of 'g'
• Confusing inactive time units
• Using seconds without 's' suffix