HOSTCACHED

HOSTCACHED is a term used to describe a caching subsystem for host information within computer networks and distributed systems. It refers to mechanisms that store mappings between host identifiers (such as hostnames or service names) and associated data (for example IP addresses, port numbers, TLS certificates, or service endpoints) to accelerate subsequent lookups and reduce load on upstream name resolution services.

Operation and architecture: A HOSTCACHED module can run on individual nodes, in edge or gateway components, or as part of a centralized service. It maintains a local cache store, plus a policy engine that governs when entries are refreshed or invalidated. Lookups first query the cache; on a miss, the module fetches information from authoritative sources such as DNS, directory services, or service registries, then stores the result with a TTL or time-bound validity. In distributed deployments, caches may be synchronized or share invalidation events to maintain coherence.

Deployment and use cases: HOSTCACHED is used to speed up virtual machine and container orchestration, microservice discovery, and enterprise networks where frequent hostname resolution occurs. It supports proactive prefetching, batch refresh, and selective invalidation to balance freshness and performance. Some systems implement host caches as a dedicated layer within the resolver stack, while others integrate caching at the application or client library level.

Benefits and challenges: The primary benefits are lower latency for name resolution, reduced DNS or directory service load, and improved resilience during partial network outages. Challenges include keeping data fresh, avoiding stale or inconsistent information, controlling cache size, and addressing security and privacy concerns if cached data is sensitive.

Relation to DNS and security: HOSTCACHED often complements DNS caching and service discovery mechanisms. Proper configuration is required to prevent cache poisoning, ensure appropriate TTL values, and enforce access controls. The concept has appeared in various forms across operating systems and network infrastructure as part of performance optimization for hostname-based traffic.