MemcachedCache

MemcachedCache is a cache adapter that stores and retrieves cached items in a Memcached cluster. It is used to implement a fast, in-memory cache for applications that run across multiple processes or servers. MemcachedCache relies on the Memcached PHP extension to communicate with a set of Memcached servers and treats the cache as a key-value store with optional expiration times.

Key management and serialization: When storing values, the adapter serializes data and uses a namespaced key (often a prefix) to prevent collisions with other caches. It supports a configurable expiration time (TTL) for items; a TTL of zero means the item never expires per Memcached rules.

Operations: Typical cache operations are supported, including get, set, delete, has, and clear. To fetch multiple values efficiently, a getMulti method is used; to write multiple values, a setMulti or individual set calls can be used. Clearing the cache usually maps to Memcached's flush command, which clears all entries in the server pool; this is a global operation across the cluster.

Limitations and considerations: Memcached is an in-memory cache with no strong durability guarantees. Items may be evicted when memory is full, and flush clears all entries. MemcachedCache is not suitable for long-term persistence and should be used as a non-critical cache layer. It requires the memcached extension and a reachable Memcached cluster; network latency and server configuration affect performance.

Relation and usage: It is commonly used as part of a caching library or framework that provides a common Cache interface (for example PSR-6 or PSR-16 compatible adapters). The MemcachedCache class is configured with server details and optional options like serializer or key prefix. It is recommended to monitor memory usage and implement appropriate memory budgeting and eviction policies.