Amarula.RetryCache.ReadOnly (amarula v0.4.1)

A read-only Amarula.RetryCache adapter backed by your message store.

Use this when your application already persists the messages it sends (an outbox, an event log, a DB table). Pointing the retry cache at that store means Amarula keeps no second copy — no ETS table, no DETS file, no max_entries to size — and the retry path reads straight from what you already have.

You own writes; Amarula only reads. This adapter implements no write side at all — it does not define the optional put/4 callback, so Amarula never even attempts a write, and never evicts or deletes anything in your store. It is your data. When a recipient asks the server for a retry, Amarula calls your get with the msg_id and expects the original message back so it can re-encrypt and resend it.

Usage

Pass a :get function fn profile, msg_id -> {:ok, entry} | :error end:

Amarula.new(%{
  profile: :primary,
  retry_cache:
    {Amarula.RetryCache.ReadOnly,
     get: fn _profile, msg_id ->
       case MyApp.Outbox.fetch(msg_id) do
         {:ok, %{to: jid, proto: %Amarula.Protocol.Proto.Message{} = m}} ->
           {:ok, %{recipient_jid: jid, message: m}}

         :error ->
           :error
       end
     end}
})

The returned map needs :recipient_jid (the wire JID the message went to) and :message (the original %Amarula.Protocol.Proto.Message{}). Return the message exactly as it was sent — a re-serialized or transformed copy may not match what the recipient is retrying against. Return :error if you no longer have it (e.g. past your own retention); Amarula then simply can't resend, which is the same outcome as a built-in cache miss.

Why a function, not a module

For the common "wrap my store" case a closure is the whole adapter. If you need more (per-profile state, a pooled connection), implement the Amarula.RetryCache behaviour directly instead — this module is just the convenient shape.