Caching, when properly configured, can instruct user's browsers to locally store and reuse previously fetched resources. This ensures faster page loads for returning users, as their browsers can retrieve resources from the local cache instead of making repeated requests to the server.
Most modern websites and web applications use browser caching to enhance the user experience. In Apache, this can be achieved using specific headers that direct the user's browser on what content should be cached and for how long. Caching in Apache can be implemented using different mechanisms such as mod_cache, mod_cache_disk, mod_mem_cache and mod_socache_shmcb, depending on the requirements and available resources.
Configuring caching in Apache involves understanding the nature of your web content, determining what content should be cached, and configuring the relevant caching directives. This may include setting expiration dates, cache size, and other parameters related to caching behavior.
$ sudo a2enmod socache_shmcb expires Enabling module socache_shmcb. Enabling module expires. To activate the new configuration, you need to run: systemctl restart apache2
Distribution with a2enmod support can simply run the command above without having to manually enable the required modules.
$ sudo vi /etc/apache2/apache2.conf
Related: Location for Apache configuration
<IfModule mod_cache_socache.c> CacheEnable socache / CacheSocache shmcb CacheSocacheMaxSize 512000 CacheDefaultExpire 3600 # Other directives as necessary </IfModule>
|CacheEnable||This directive defines the storage type and the URL space for the cache. Example: CacheEnable socache / enables memory-based caching (using shared object cache) for all URLs.|
|CacheSocache||Defines the shared object cache provider to use for caching. In this case, shmcb indicates using a shared memory mechanism for storage.|
|CacheSocacheMaxSize||Sets the maximum amount of shared memory storage in bytes. In this example, 512000 bytes (or 0.5MB) is allocated for the cache storage.|
|CacheDefaultExpire||Determines the default expiration time in seconds for cached content. If no expiration time is specified in the HTTP headers, this value is used. Example: 3600 sets a default expiration time of one hour.|
<FilesMatch ".(jpg|jpeg|png|gif|js|css)$"> ExpiresActive On ExpiresDefault "access plus 1 month" </FilesMatch>
$ sudo systemctl restart apache2 # Ubuntu and Debian $ sudo systemctl restart httpd # CentOS and Red Hat
$ curl -I https://www.example.com/image.png HTTP/1.1 200 OK Date: Fri, 25 Aug 2023 09:13:40 GMT Server: Apache/2.4.55 (Ubuntu) Last-Modified: Fri, 25 Aug 2023 08:57:56 GMT ETag: "1f61-603bb8a696d78" Accept-Ranges: bytes Content-Length: 8033 Cache-Control: max-age=2592000 Expires: Sun, 24 Sep 2023 09:13:40 GMT Content-Type: image/png
Look for headers like Cache-Control and ETag in the response to confirm caching.
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