Files
familienarchiv/ocr-service
Marcel 1aca4c4a41 security(ocr): add non-root user and set HOME/HF_HOME in Dockerfile
CIS Docker §4.1: run uvicorn as UID 1000 (ocr) instead of root.
Creates /home/ocr and /app/cache with correct ownership so named
volumes inherit ocr:ocr on first Docker mount. Sets HOME and HF_HOME
so ~ expansion and Hugging Face caching resolve under /app, not /root.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-05-17 16:46:25 +02:00
..

ocr-service

Python FastAPI microservice that performs the actual handwritten text recognition (HTR) and OCR. The Spring Boot backend orchestrates jobs; this service executes them.

What this service owns

  • Text recognition: Surya (typewritten text) and Kraken (Kurrent/Sütterlin historical handwriting)
  • Baseline layout analysis: Kraken BLLA model
  • Sender recognition: trained per-archive sender models
  • HTTP API at port 8000 (internal Docker network — no external port)

What this service does NOT own

  • Job lifecycle — tracked in the backend's ocr/ domain
  • MinIO storage — the service fetches PDFs via presigned URLs generated by the backend; it does not hold credentials
  • Transcription block storage — results are streamed back to the backend, which writes them to PostgreSQL

API endpoints

Endpoint Auth Purpose
POST /ocr None (internal network only) Run OCR on a PDF (presigned MinIO URL in request body)
POST /train X-Training-Token header Trigger sender-model training
POST /segtrain X-Training-Token header Trigger segmentation training
GET /health None Health check

Environment variables

Variable Default Required? Sensitive? Purpose
TRAINING_TOKEN YES (prod) YES Guards /train and /segtrain. Do not leave empty in production.
ALLOWED_PDF_HOSTS minio,localhost,127.0.0.1 YES SSRF protection — comma-separated allowed PDF source hosts. Never set to *.
KRAKEN_MODEL_PATH /app/models/ Directory where Kraken HTR models are stored (populated by download-kraken-models.sh)
BLLA_MODEL_PATH /app/models/blla.mlmodel Kraken baseline layout analysis model. Auto-downloaded via ensure_blla_model.py on startup if missing.

Key files

File Purpose
main.py FastAPI app, endpoint definitions, SSRF validation
engines/ Surya and Kraken engine wrappers
models.py Pydantic request/response models
preprocessing.py PDF-to-image conversion before OCR
confidence.py Per-block confidence scoring
spell_check.py Post-OCR spell correction using historical dictionaries
ensure_blla_model.py Startup script that downloads the BLLA model if missing
entrypoint.sh Docker entrypoint — runs ensure_blla_model.py then starts the server

Backend counterpart

backend/src/main/java/org/raddatz/familienarchiv/ocr/README.md