Compressed Database Cache Backend

This module provides a cache backend which leverages gzip compression for the
stored data.

Upon cache set the cache data will be gzipped, if the gzipped data is smaller
than the original data the compressed data will be stored in the cache bin.

This Database Backend adds two additional states to serialized column of Drupal
cores DatabaseBackend.

- SERIALIZED_COMPRESSED (2): a serialized object, compressed.
- STRING_SERIALIZED_COMPRESSED (3): a compressed string.

Benchmark

100k+ nodes, same time needed for generation as with the default database backend. Storage comparison:

bin default database backend (total size in MB) compressed cache database backend (total size in MB) reduction in % cache_data 4385,48 532,48 87,85811359 cache_dynamic_page_cache 12419,56 4486,42 63,87617597 cache_page 20641,09 5701,08 72,37994699 cache_render 7026,89 3110,8 55,73005981

Please add your findings to Benchmarks, comparison

Requirements

php functions: gzcompress, gzuncompress come with zlib extension.

Installation

download and install the module as ususal.

Swap the existing database backend with our compressed one in settings.php:

    // Default cache bin
    $settings['cache']['default'] = 'cache.backend.database_compressed_cache';
    // Specific cache bins
    $settings['cache']['bins']['data'] = 'cache.backend.database_compressed_cache';
    $settings['cache']['bins']['dynamic_page_cache'] = 'cache.backend.database_compressed_cache';
    $settings['cache']['bins']['render'] = 'cache.backend.database_compressed_cache';
    $settings['cache']['bins']['page'] = 'cache.backend.database_compressed_cache';

Advanced settings

/**
     * Compression level
     * default = 6
     * @see http://php.net/gzcompress
     */
    $settings['compressed_cache']['cache_compression_ratio'] = 1;

    /**
     * Minimum string length to add compression.
     * Seems to be completely based on gut feeling. can not find any sources googling this topic.
     */
    $settings['compressed_cache']['cache_compression_size_threshold'] = 100;
    
    /**
     * Whether garbage collection is enabled or not. Defaults to TRUE.
     */
    $settings['compressed_cache']['garbage_collection_enabled'] = TRUE;

Related issues

• Compress cache data before storing it in the database
• Make serializer customizable for Cache\DatabaseBackend
• Cache backend should use the serializer service.