View Source Finitomata.Cache (Finitomata v0.29.0)

The self-curing cache based on Finitomata implementation.

This implementation should not be chosen for typical caching scenarios, use cachex and/or con_cache instead.

The use-case for this implementation would be somewhat like a self-updated local replica of the remote data. Unlike typical cache implementations, this one might keep the cached values up-to-date, configured by ttl: argument. Bsaed on processes (backed by Finitomata,) this implementation updates itself periodically, making the value retrieval almost instant.

Consider a remote service supplying currency exchange rates by polling. One might instruct Finitomata.Cache to retrieve values periodically (say, once per a minute,) and then the consumers of this cache would be able to retrieve the up-to-date values locally without a penalty of getting a value after a long period (cache miss.)

First of all, the Finitomata.Cache implementation should be added to a supervision tree

  {Finitomata.Cache, [
    [id: MyCache, ttl: 60_000, live?: true, type: Infinitomata, getter: &MyMod.getter/1]]}

Once the supervisor is started, the values might be retrieven as

  Finitomata.Cache.get(MyCache, :my_key_1, live?: false) # use default getter
  Finitomata.Cache.get(MyCache, :my_key, getter: fn _ -> ExtService.get(:my_key) end)

Summary

Functions

child_spec(opts \\ [])
erase(id, key)

Erases the cache assotiated with key.

get(id, key, opts \\ [])

Retrieves the value either cached or via getter/1 anonymous function and caches it.

start_link(opts \\ [])

Supervision tree embedder.

Functions

child_spec(opts \\ [])

(since 0.26.0) 
@spec child_spec(
  id: term(),
  type: term(),
  ttl: pos_integer(),
  live?: boolean(),
  getter: (term() -> term()) | term()
) :: Supervisor.child_spec()

erase(id, key)

(since 0.26.0) 
@spec erase(id :: Finitomata.id(), key :: any()) :: :ok

Erases the cache assotiated with key.

get(id, key, opts \\ [])

(since 0.26.0) 
@spec get(
  id :: Finitomata.id(),
  key :: key,
  opts :: [
    getter: (key -> value),
    live?: boolean(),
    reset: boolean(),
    ttl: pos_integer()
  ]
) :: {DateTime.t(), value} | {:instant, value} | :error
when key: any(), value: any()

Retrieves the value either cached or via getter/1 anonymous function and caches it.

Spawns the respective Finitomata instance if needed.

start_link(opts \\ [])

(since 0.26.0) 
@spec start_link(
  id: term(),
  type: term(),
  ttl: pos_integer(),
  live?: boolean(),
  getter: (term() -> term()) | term()
) :: Supervisor.on_start()

Supervision tree embedder.

  • :id (term/0) - Required. The unique ID of this Finitomata “branch,” when nil the Finitomata.Cache value would be used

  • :type - The actual Finitomata.Supervisor implementation (typically, Finitomata or Infinitomata) The default value is Infinitomata.

  • :ttl (pos_integer/0) - Required. The default time-to-live value in seconds, after which the value would be either revalidated or discarded

  • :live? (boolean/0) - When true, the value will be automatically renewed upon expiration (and discarded otherwise) The default value is false.

  • :getter - The shared for all instances getter returning a value based on the name of the instance, used as a key The default value is nil.