Finitomata.Persistency.DETS (Finitomata v0.41.0)

Built-in disk-durable Finitomata.Persistency adapter backed by a :dets file.

It behaves exactly like Finitomata.Persistency.ETS (one {state, payload} snapshot per FSM, keyed by the FSM name) but the table is persisted to disk, so snapshots survive a full node restart. Both adapters are OTP built-ins and add no dependencies.

Single node

:dets is a single-node, single-file store with a 2GB file-size limit. For multi-node or large-scale persistence, back the FSM with a database via a custom Finitomata.Persistency implementation (for example through Finitomata.Persistency.Persistable).

Usage

Add the table owner to your supervision tree and point use Finitomata at this module:

children = [
  Finitomata.Persistency.DETS,
  {Finitomata.Supervisor, id: MyApp.Fsm}
]

defmodule MyApp.Order do
  use Finitomata, fsm: @fsm, persistency: Finitomata.Persistency.DETS
end

Configuration

The :dets file path (and optionally the table name) are configurable. The default path lives under System.tmp_dir!/0; set a stable location for production:

config :finitomata, Finitomata.Persistency.DETS,
  file: "/var/lib/my_app/finitomata.dets",
  table: :my_fsm_snapshots

Summary

Functions

file()

The :dets file path in use (configurable via config :finitomata, Finitomata.Persistency.DETS)

get(name)

Reads the snapshot stored for name, or nil

last_error(name)

Reads the last persisted failure for name, or nil

purge(name)

Removes the snapshot and the last error stored for name

start_link(opts \\ [])

Starts the process owning the snapshot file; add it to your supervision tree

sync()

Flushes pending writes to disk

table()

The :dets table name in use (configurable via config :finitomata, Finitomata.Persistency.DETS)