# Annotations (realtime & stream sync)

## 1. High-Level Overview

**Purpose:** **SSE** push for annotation changes and **RabbitMQ Stream** failsafe export — `01_annotations.md` sections *SSE Communication* and *Annotation Sync* / *Failsafe* / *RabbitMQ Stream*.

**Architectural pattern:** Event channel + background outbox producer.

**Upstream dependencies:** Platform (DB, config, paths), Annotations REST (domain mutations enqueue/publish).

**Downstream consumers:** Browser UI (SSE); Admin sync worker; AI Training consumer (external).

## 2. Internal interfaces

- `AnnotationEventService` — in-process `Channel<AnnotationEventDto>`; `PublishAsync` / `Reader`.
- `FailsafeProducer` + `RabbitMqConfig` — stream client, MessagePack payloads, drains `annotations_queue_records`.
- **HTTP:** `AnnotationsController.Events` — `text/event-stream` subscription (same controller file as REST component; **doc ownership** here for SSE).

## 3. External API / integration

| Surface | Notes |
|---------|--------|
| `GET /annotations/events` | SSE; see suite SSE section |
| RabbitMQ stream `azaion-annotations` | Env `RABBITMQ_*` from `Program` |

## 4. Data access patterns

Queue table buffering; stream send on connectivity; image bytes in create messages per suite.

## 5. Caveats

MessagePack key stability; stream consumer offsets independent per consumer type.

## 6. Dependency graph

**Imports from:** Platform, annotations domain (via service calls / shared types). **Consumed by:** External infrastructure.

## 7. Modules included

`sse-realtime`, `rabbitmq-stream-sync`.