Add FastAPI hello-world structure with Docker and DB health check

- app/main.py: root endpoint + /health that reports DB connectivity
- app/db.py: pymysql connection check from MYSQL_* env vars, logged at startup
- Dockerfile: python:3.12-slim, port 8720
- docker-compose.yml: mysql:8.2 with healthcheck, app waits for DB ready
- requirements.txt: fastapi, uvicorn, pymysql

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

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+FROM python:3.12-slim
+
+WORKDIR /app
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY app/ ./app/
+
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8720", "--log-level", "info"]

app/db.py

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+import os
+import pymysql
+
+
+def _params() -> dict:
+    return {
+        "host": os.environ["MYSQL_HOST"],
+        "port": int(os.environ.get("MYSQL_PORT", 3306)),
+        "user": os.environ["MYSQL_USER"],
+        "password": os.environ["MYSQL_PASSWORD"],
+        "database": os.environ["MYSQL_DATABASE"],
+        "connect_timeout": 3,
+    }
+
+
+def check_db() -> bool:
+    try:
+        conn = pymysql.connect(**_params())
+        conn.close()
+        return True
+    except Exception:
+        return False

app/main.py

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+import logging
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+
+from app.db import check_db
+
+logger = logging.getLogger("pops")
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    if check_db():
+        logger.info("Database connection OK")
+    else:
+        logger.warning("Database unreachable — check MYSQL_* environment variables")
+    yield
+
+
+app = FastAPI(title="POPS", lifespan=lifespan)
+
+
+@app.get("/")
+def root():
+    return {"message": "Hello from POPS"}
+
+
+@app.get("/health")
+def health():
+    db_ok = check_db()
+    return {
+        "status": "ok" if db_ok else "degraded",
+        "db": "connected" if db_ok else "unreachable",
+    }

docker-compose.yml

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+services:
+  db:
+    image: mysql:8.2
+    restart: unless-stopped
+    env_file: .env
+    volumes:
+      - mysql_data:/var/lib/mysql
+      - ./db.sql:/docker-entrypoint-initdb.d/01_schema.sql
+    healthcheck:
+      test: ["CMD", "mysqladmin", "ping", "-h", "127.0.0.1", "--silent"]
+      interval: 10s
+      timeout: 5s
+      retries: 10
+      start_period: 30s
+
+  app:
+    build: .
+    ports:
+      - "8720:8720"
+    env_file: .env
+    environment:
+      MYSQL_HOST: db      # override localhost → compose service name
+    depends_on:
+      db:
+        condition: service_healthy
+    restart: unless-stopped
+
+volumes:
+  mysql_data:

requirements.txt

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+fastapi==0.115.6
+uvicorn[standard]==0.34.0
+pymysql==1.1.1