# Flow F4 — Failsafe Outbox Drain → RabbitMQ Stream

Cross-reference: `system-flows.md` → Flow F4.

## Sequence

```mermaid
sequenceDiagram
    autonumber
    participant FP as FailsafeProducer (02, IHostedService)
    participant DB
    participant Path as PathResolver (06)
    participant FS as Filesystem
    participant RMQ as RabbitMQ Stream "azaion-annotations"

    loop while host running
        FP->>DB: SELECT FROM annotations_queue_records
        DB-->>FP: pending rows (operation, annotation_ids JSON)
        loop per row
            alt operation = Created
                FP->>Path: GetImagePath(annotationId)
                FP->>FS: read bytes
            end
            FP->>FP: serialize MessagePack (Annotation*QueueMessage)
            FP->>RMQ: publish stream entry
            alt publish ok
                FP->>DB: DELETE annotations_queue_records WHERE id = :id
            else stream unavailable
                FP->>FP: log + backoff
            end
        end
    end
```

## State

```mermaid
stateDiagram-v2
    [*] --> Idle
    Idle --> Draining: queue rows present
    Draining --> Publishing: row picked
    Publishing --> Acked: stream publish ok
    Acked --> Idle: row deleted
    Publishing --> Backoff: stream unavailable
    Backoff --> Idle: backoff elapsed
```

## Notes

- See ADR-003 in `architecture.md` for rationale.
- Multi-instance drain: no leasing in DB → duplicate stream entries possible. Suite consumer contract should dedupe.
- Bulk message (`AnnotationBulkQueueMessage`) carries multiple annotation ids; `Created` semantics on bulk are out of scope here — confirm during Step 4 verification.