Storage and embedding

Kathikon persists jobs in Mnesia via Kathikon.Storage, backed by Kathikon.Backend.Storage.Mnesia.

Automatic startup

When Kathikon is a dependency, Kathikon.Application runs on boot:

1. Kathikon.Storage.setup/0 — Mnesia schema + :kathikon_jobs table
2. Starts Registry, Queue supervisor, Scheduler, Pruner
3. Kathikon.Queue.start_configured/0 — dispatchers for configured queues

No manual Mnesia setup is required in a standard Phoenix or Mix release.

Manual embedding

If you start Kathikon outside its application (scripts, Livebook, tests):

Application.put_env(:kathikon, :mnesia_copies, :ram)

{:ok, _} = Application.ensure_all_started(:kathikon)
# or, without full app:
:ok = Kathikon.Storage.setup()

Livebook

Livebook nodes are named but lack a Mnesia disc directory. Use RAM copies:

Mix.install(
  [{:kathikon, path: "..", env: :prod}],
  config: [kathikon: [mnesia_copies: :ram, poll_interval: 150, ...]]
)

See the interactive demo.

Test helpers

# Clear jobs between integration tests
:ok = Kathikon.Storage.clear_jobs!()

# Facade tests (Kathikon.cancel/1, Kathikon.fetch/1) — mock scoped to the test process
Kathikon.TestSupport.use_mock_storage!(context)

# Runtime unit tests — inject storage at start_link/1
{:ok, pid} =
  Kathikon.Dispatcher.start_link(
    queue: :test,
    config: [concurrency: 1],
    storage: Kathikon.Backend.Storage.Mock
  )

Mox.allow(Kathikon.Backend.Storage.Mock, self(), pid)

Do not reconfigure the global storage_backend in tests. The application scheduler, pruner, and dispatchers always use Mnesia configured at boot. Mock tests start their own processes with storage: or scope mocks with use_mock_storage!/1.

clear_jobs!/0 and reset!/0 are intended for tests — not public production APIs.

Storage facade

Kathikon.Storage delegates to a configurable backend:

Application code should use Kathikon.insert/3 rather than calling Storage directly.

Backend plug-in

config :kathikon, storage_backend: Kathikon.Backend.Storage.Mnesia

The behaviour is Kathikon.Backend.Storage. Phase 1 ships one implementation (Kathikon.Backend.Storage.Mnesia). Future phases add lease and cron backends under Kathikon.Backend.*.

Tables

Queue configuration lives in config :kathikon, queues: (Kathikon.Config), not in Mnesia.

Related

• Configuration — mnesia_copies, storage_backend
• Module reference: Kathikon.Storage