Module hitbox::states

The set of states of the Hitbox finite state machine.

Motivation

Different caching options are suitable for different load profiles. We devised Hitbox as a one-stop solution and therefore provide several different caching policies. They are all described in CacheSettings. The behavior of Hitbox depends on which caching policy option is selected, which means that all Hitbox actions depend on the Initial state. To implement caching logic that depends on the initial state, we chose a finite state machine. State machine transitions are defined by the transition_groups module and correspond to the CacheSettings options.

States shouldn’t depend on specific implementations of the cache backend and upstream, and to interact with them, many states contain an adapter field. The adapter provides the necessary operations such as getting the cache by key, saving the cache, etc.

States

The states module is a set of states of the Hitbox finite state machine.

Modules

cache_policy	Defines whether the result returned from upstream will be cached.
cache_polled	Defines the state of the data that was retrieved from the cache.
cache_updated	The state that Hitbox enters after updating the cache.
finish	Final state of Hitbox.
initial	Initial state of Hitbox.
upstream_polled	Defines the state of the data that was retrieved from the upstream.