🎉 Initial commit

api/main.py

@@ -0,0 +1,132 @@
+"""FastAPI service exposing telemetry data from TimescaleDB over HTTPS.
+
+Requires mutual TLS: clients must present a certificate signed by the CA.
+Requests are served from a pool of database connections, so each request
+reuses an established session instead of paying connect/auth costs.
+"""
+
+import os
+from contextlib import asynccontextmanager
+from typing import Any, Final, Optional
+
+import psycopg
+from fastapi import FastAPI, HTTPException, Query, Request
+from fastapi.responses import JSONResponse
+from psycopg import sql
+from psycopg.rows import dict_row
+from psycopg_pool import ConnectionPool
+
+_SELECT_SQL: Final = "SELECT time, topic, device_id, payload FROM telemetry"
+
+# Connections use row_factory=dict_row, so each row is a dict.
+_DictConnection = psycopg.Connection[dict[str, Any]]
+
+pool: Optional[ConnectionPool[_DictConnection]] = None
+
+
+def _connect_kwargs() -> dict[str, Any]:
+    return {
+        "host": os.getenv("DB_HOST", "timescaledb"),
+        "port": int(os.getenv("DB_PORT", "5432")),
+        "dbname": os.getenv("DB_NAME", "telemetry"),
+        "user": os.getenv("DB_USER", "ingester"),
+        "password": os.getenv("DB_PASSWORD", "changeme"),
+        "row_factory": dict_row,
+    }
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    global pool
+    # Subscripting solves the pool's invariant connection type; row_factory
+    # in kwargs makes every pooled connection return dict rows.
+    server_pool = ConnectionPool[_DictConnection](
+        kwargs=_connect_kwargs(),
+        min_size=int(os.getenv("DB_POOL_MIN_SIZE", "2")),
+        max_size=int(os.getenv("DB_POOL_MAX_SIZE", "10")),
+    )
+    server_pool.open(wait=False)
+    pool = server_pool
+    try:
+        yield
+    finally:
+        pool = None
+        server_pool.close()
+
+
+app = FastAPI(title="MQTT Telemetry API", lifespan=lifespan)
+
+
+def get_pool() -> ConnectionPool[_DictConnection]:
+    if pool is None:
+        raise RuntimeError("Database pool not initialized")
+    return pool
+
+
+@app.middleware("http")
+async def require_client_cert(request: Request, call_next):
+    # uvicorn populates the client cert into the transport when mTLS is enabled.
+    cert = getattr(request.scope.get("transport"), "get_extra_info", lambda _: None)(
+        "peercert"
+    )
+    if cert is None:
+        # Return a response directly: HTTPException raised from middleware is
+        # not handled by the (inner) exception handlers and would surface
+        # as a 500.
+        return JSONResponse(status_code=401, content={"detail": "Client certificate required"})
+    return await call_next(request)
+
+
+@app.get("/health")
+def health() -> dict[str, str]:
+    return {"status": "ok"}
+
+
+def _telemetry_query(
+    topic: Optional[str], device_id: Optional[str], limit: int
+) -> tuple[sql.Composed, list[Any]]:
+    """Build the SELECT for the requested filters as composed SQL.
+
+    The statement is composed with psycopg.sql, and all values are bound
+    as parameters, so nothing is interpolated into the query string.
+    """
+    conditions: list[sql.Composable] = []
+    params: list[Any] = []
+    if topic:
+        conditions.append(sql.SQL("topic = %s"))
+        params.append(topic)
+    if device_id:
+        conditions.append(sql.SQL("device_id = %s"))
+        params.append(device_id)
+    query = sql.SQL(_SELECT_SQL)
+    if conditions:
+        query += sql.SQL(" WHERE ") + sql.SQL(" AND ").join(conditions)
+    query += sql.SQL(" ORDER BY time DESC LIMIT %s")
+    params.append(limit)
+    return query, params
+
+
+@app.get("/telemetry")
+def list_telemetry(
+    topic: Optional[str] = Query(default=None),
+    device_id: Optional[str] = Query(default=None),
+    limit: int = Query(default=100, le=1000),
+) -> list[dict[str, Any]]:
+    query, params = _telemetry_query(topic, device_id, limit)
+    with get_pool().connection() as conn, conn.cursor() as cur:
+        cur.execute(query, params)
+        return cur.fetchall()
+
+
+@app.get("/telemetry/latest")
+def latest_telemetry(
+    topic: Optional[str] = Query(default=None),
+    device_id: Optional[str] = Query(default=None),
+) -> Optional[dict[str, Any]]:
+    query, params = _telemetry_query(topic, device_id, 1)
+    with get_pool().connection() as conn, conn.cursor() as cur:
+        cur.execute(query, params)
+        row = cur.fetchone()
+        if row is None:
+            raise HTTPException(status_code=404, detail="No data found")
+        return row