docling-studio/docs/architecture.md
Pier-Jean Malandrino fe83dcdf79 feat(settings): paste-image size/type limits for #195 (#196)
* docs: rename Clean Architecture → Hexagonal Architecture (ports & adapters)

Le backend suit le pattern ports & adapters (ports dans domain/ports.py,
adaptateurs dans infra/), pas Clean Architecture au sens Uncle Bob.
Aligne la terminologie dans README, docs/architecture.md, ADR guide,
audit master, fiche audit 01, et la nav mkdocs.

Les noms de fichiers et la commande /audit:clean-architecture restent
stables pour preserver les liens croises et les skills existants.

* feat(settings): add paste-image size/type limits surfaced via /api/health

Introduces MAX_PASTE_IMAGE_SIZE_MB (default 10) and
PASTE_ALLOWED_IMAGE_TYPES (default image/png,image/jpeg,image/webp)
env vars so the upcoming Verify-mode clipboard-paste handler can
validate client-side against the same limits the backend enforces.

Follows the existing MAX_FILE_SIZE_MB pattern. Ships the accepted
design doc at docs/design/195-copy-paste-image-verify-mode.md.

Refs #195
2026-04-29 14:00:00 +02:00

210 lines
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# Architecture
## Overview
![Docling Studio architecture](images/global.png){ width="700" }
Two services communicating via REST. The frontend is a Vue 3 SPA served by Nginx in production. The backend is a FastAPI app that wraps Docling's document conversion engine.
### Zooming into the backend
The schema above shows the macro view. Inside the backend, the code follows a **Hexagonal Architecture** (ports & adapters) with strict layer boundaries:
```
┌──────────────────────────────────────────────────────┐
│ Backend │
│ │
│ ┌──────────┐ │
│ │ api/ │ ← HTTP (FastAPI routes, Pydantic) │
│ └────┬─────┘ │
│ │ calls │
│ ┌────▼─────┐ │
│ │services/ │ ← Use case orchestration │
│ └──┬────┬──┘ │
│ │ │ │
│ ┌───▼──┐ ┌▼───────────┐ │
│ │domain│ │persistence/ │ │
│ │ │ │ │ │
│ │bbox │ │ SQLite CRUD │ ← Storage (your blue box) │
│ │parse │ │ file store │ │
│ └──────┘ └─────────────┘ │
│ ↑ pure Python, no deps ↑ aiosqlite │
└──────────────────────────────────────────────────────┘
```
Dependencies flow **inward**: `api → services → domain`. The domain layer has zero knowledge of HTTP or database.
## Backend — Hexagonal Architecture (ports & adapters)
The backend follows the hexagonal / ports-and-adapters pattern. The domain layer defines **ports** (abstract protocols in `domain/ports.py`); `infra/` provides **adapters** that implement them. Dependencies flow inward: API → Services → Domain. The domain layer has zero knowledge of HTTP, database, or any framework.
```
document-parser/
├── main.py # FastAPI app, CORS, lifespan, health endpoint
├── domain/ # Pure domain — no HTTP, no DB
│ ├── models.py # Document, AnalysisJob dataclasses
│ ├── ports.py # Abstract protocols (DocumentConverter, DocumentChunker)
│ ├── value_objects.py # ConversionResult, ChunkingOptions, ChunkResult
│ └── bbox.py # Bounding box coordinate normalization
├── api/ # HTTP layer (FastAPI routers)
│ ├── schemas.py # Pydantic DTOs (camelCase serialization)
│ ├── documents.py # /api/documents endpoints
│ └── analyses.py # /api/analyses endpoints (create, rechunk, delete)
├── persistence/ # Data layer (SQLite via aiosqlite)
│ ├── database.py # Connection management, schema init
│ ├── document_repo.py # Document CRUD
│ └── analysis_repo.py # AnalysisJob CRUD
├── infra/ # Infrastructure adapters
│ ├── settings.py # Environment-based configuration
│ ├── local_converter.py # In-process Docling converter (local mode)
│ ├── serve_converter.py # HTTP client for Docling Serve (remote mode)
│ ├── local_chunker.py # In-process chunking (HierarchicalChunker, HybridChunker)
│ ├── rate_limiter.py # Sliding-window rate limiting middleware
│ └── bbox.py # Bbox coordinate normalization helpers
├── services/ # Use case orchestration
│ ├── document_service.py # Upload, delete, preview
│ └── analysis_service.py # Async Docling processing + chunking
└── tests/ # pytest (199 tests)
```
### Layer responsibilities
| Layer | Role | Depends on |
|-------|------|------------|
| **domain** | Dataclasses, value objects, abstract ports | Nothing (pure Python) |
| **persistence** | SQLite CRUD, aiosqlite | domain (models) |
| **infra** | Adapters: converters, chunker, rate limiter, settings | domain (ports, value objects) |
| **services** | Orchestrate use cases, call converters/chunkers | domain + persistence + infra |
| **api** | HTTP endpoints, Pydantic DTOs, error handling | services |
### API contract
The API uses **camelCase** serialization (via Pydantic `alias_generator`), while the backend uses **snake_case** internally. The `pages_json` field contains raw `dataclasses.asdict()` output, so page data uses **snake_case** (`page_number`, not `pageNumber`).
## Frontend — Feature-Based
The frontend is organized by feature, each with its own store, API client, and UI components.
```
frontend/src/
├── app/ # App shell, router, global styles
├── pages/ # Route-level pages
│ ├── HomePage.vue
│ ├── StudioPage.vue # PDF viewer + config + results
│ ├── DocumentsPage.vue
│ ├── HistoryPage.vue
│ └── SettingsPage.vue
├── features/ # Feature modules
│ ├── analysis/ # Analysis store, API, bbox scaling, UI
│ │ ├── store.ts
│ │ ├── api.ts
│ │ ├── bboxScaling.ts # Pure math: page coords → pixel coords
│ │ └── ui/
│ │ ├── BboxOverlay.vue
│ │ ├── AnalysisPanel.vue
│ │ ├── StructureViewer.vue
│ │ └── ...
│ ├── chunking/ # Chunk panel UI + rechunk action
│ ├── document/ # Document store, API, upload
│ ├── feature-flags/ # Feature flag store (reads /api/health)
│ ├── history/ # History store, navigation
│ └── settings/ # Theme, locale, API URL
└── shared/ # Cross-feature utilities
├── types.ts # All shared TypeScript interfaces
├── i18n.ts # FR/EN translations
├── format.ts # Date/size formatters
└── api/http.ts # HTTP client (fetch wrapper)
```
### Data flow
```
User action → Pinia store action → API client (fetch) → Backend REST endpoint
Backend response → Pinia store state → Vue reactivity → UI update
```
### Key design decisions
- **Pinia stores** per feature, not global. Each feature owns its state.
- **TypeScript strict mode** with shared interfaces in `shared/types.ts`.
- **No component library** — custom CSS with CSS variables for theming.
- **vue-tsc** in CI to catch type errors before merge.
## Feature Flags
The frontend adapts its UI based on the backend's capabilities. On startup, the feature flag store fetches `/api/health` and reads the `engine` and `deploymentMode` fields.
| Flag | Condition | Effect |
|------|-----------|--------|
| `chunking` | `engine === 'local'` | Shows chunking options in the analysis panel |
| `disclaimer` | `deploymentMode === 'huggingface'` | Shows a disclaimer banner at the top of the app |
This allows the same frontend build to work with both local and remote backends without conditional compilation.
## Rate Limiting
The backend applies a sliding-window rate limiter as middleware:
- **60 requests** per **60 seconds** per client IP
- The `/api/health` endpoint is excluded
- When the limit is exceeded, the API returns `429 Too Many Requests` with a `Retry-After` header
## Analysis Lifecycle
An analysis job follows this state machine:
```
PENDING → RUNNING → COMPLETED
→ FAILED
```
| Status | Description |
|--------|-------------|
| `PENDING` | Job created, waiting for a processing slot |
| `RUNNING` | Docling conversion in progress |
| `COMPLETED` | Conversion finished — results available (markdown, HTML, pages, chunks) |
| `FAILED` | Conversion error — `error_message` contains details |
The backend limits parallel jobs via `MAX_CONCURRENT_ANALYSES` (default: 3) to avoid overloading the CPU during Docling processing.
## Local vs Remote Mode
The backend supports two conversion engines, selected via the `CONVERSION_ENGINE` environment variable:
| | Local | Remote |
|---|---|---|
| **Engine** | In-process Docling (PyTorch) | HTTP client to [Docling Serve](https://github.com/DS4SD/docling-serve) |
| **Chunking** | Available (in-process) | Not available |
| **Docker image** | `latest-local` (~1.9 GB) | `latest-remote` (~270 MB) |
| **ML models** | Downloaded on first run (~400 MB) | Managed by Docling Serve |
| **CPU/RAM** | 4+ CPUs, 6+ GB RAM | 2 CPUs, 2 GB RAM |
The converter is selected at startup in `main.py` via `_build_converter()`. The chunker (`_build_chunker()`) is only instantiated in local mode — in remote mode, the chunking feature flag is disabled and the UI hides the chunking panel.
## Health Endpoint
`GET /api/health` returns the backend status:
```json
{
"status": "ok",
"engine": "local",
"version": "0.3.0",
"deploymentMode": "self-hosted"
}
```
The frontend uses this response to:
1. Verify the backend is reachable
2. Evaluate feature flags (chunking, disclaimer)
3. Display the app version