# `Rheo.DeadLetter`
[🔗](https://github.com/thanos/rheo/blob/v1.0.0/lib/rheo/dead_letter.ex#L1)

Portable dead-letter (DLQ) row for ops inspection.

**DLQ** = dead-letter queue: a delivery that stopped being retried for a
consumer group (after `Rheo.reject/3` or exhausted nack attempts). The
underlying stream event is unchanged; only that group's delivery is
dead-lettered.

Backends may store rejects as delivery-row status flips (ETS/Mongo/Ecto) or as
a separate DLQ stream (Redis). This struct is the normalized read shape for
`Rheo.dead_letters/3`.

## Fields

| Field | Type | Meaning |
|---|---|---|
| `stream` | `String.t()` | Stream name |
| `group` | `String.t()` | Consumer group that dead-lettered the delivery |
| `event_id` | `String.t()` | Stable `Rheo.Event.id` |
| `partition` | `non_neg_integer()` | Partition of the event |
| `sequence` | `non_neg_integer() \| nil` | Sequence when known |
| `reason` | `term()` | Reject/retry reason recorded by the backend |
| `dead_lettered_at` | `DateTime.t() \| nil` | When the delivery became dead-lettered |
| `event` | `Rheo.Event.t() \| nil` | Embedded event when the backend includes it |

## Example

    iex> dl = %Rheo.DeadLetter{
    ...>   stream: "market-events",
    ...>   group: "risk",
    ...>   event_id: "evt_01",
    ...>   partition: 0,
    ...>   sequence: 3,
    ...>   reason: :invalid_schema,
    ...>   dead_lettered_at: ~U[2026-01-15 12:00:00.000Z],
    ...>   event: nil
    ...> }
    iex> {dl.group, dl.reason}
    {"risk", :invalid_schema}

# `t`

```elixir
@type t() :: %Rheo.DeadLetter{
  dead_lettered_at: DateTime.t() | nil,
  event: Rheo.Event.t() | nil,
  event_id: String.t(),
  group: String.t(),
  partition: non_neg_integer(),
  reason: term(),
  sequence: non_neg_integer() | nil,
  stream: String.t()
}
```

One dead-lettered delivery for ops listing.

See the module documentation for field meanings.

---

*Consult [api-reference.md](api-reference.md) for complete listing*