backend: Handling temperature sensor not available error

apps/rasptherm-backend/rasptherm_backend/models/error.py

@@ -0,0 +1,9 @@
+from pydantic import BaseModel
+
+
+class ErrorDetailModel(BaseModel):
+    msg: str
+
+
+class ServiceNotAvailableModel(BaseModel):
+    detail: ErrorDetailModel

apps/rasptherm-backend/rasptherm_backend/routers/sensor.py

@@ -1,15 +1,22 @@
 from typing import Annotated
 
-from fastapi import APIRouter, Depends
+from fastapi import APIRouter, Depends, status
 
+from rasptherm_backend.models.error import ServiceNotAvailableModel
 from rasptherm_backend.models.sensor import ReadSensorModel
-from rasptherm_backend.services.sensor import Sensor, get_sensor
+from rasptherm_backend.services.sensor import get_sensor
 from rasptherm_backend.services.sensor import read_sensor as _read_sensor
+from rasptherm_backend.types.sensor import Sensor
 
 sensor_router = APIRouter(prefix="/sensor", tags=["sensor"])
 
 
-@sensor_router.get("/read")
+@sensor_router.get(
+    "/read",
+    responses={
+        status.HTTP_503_SERVICE_UNAVAILABLE: {"model": ServiceNotAvailableModel}
+    },
+)
 async def read_sensor(
     sensor: Annotated[Sensor, Depends(get_sensor)],
 ) -> ReadSensorModel:

apps/rasptherm-backend/rasptherm_backend/services/sensor.py

@@ -1,17 +1,14 @@
 from collections.abc import AsyncIterator
-from typing import Annotated, Protocol
+from typing import Annotated
 
 from fastapi import Depends
 from rasptherm_sensor.client import non_ssl_sensor_connection, ssl_sensor_connection
-from rasptherm_sensor.types import SensorReadout
 
 from rasptherm_backend.models.sensor import ReadSensorModel
 from rasptherm_backend.services.certs import read_sensor_certs
 from rasptherm_backend.services.settings import Settings, get_settings
-
-
-class Sensor(Protocol):
-    async def read_sensor(self) -> SensorReadout: ...
+from rasptherm_backend.types.sensor import Sensor
+from rasptherm_backend.utils.sensor import sensor_not_available_handling
 
 
 async def get_sensor(
@@ -34,6 +31,7 @@ async def get_sensor(
         yield sensor
 
 
+@sensor_not_available_handling
 async def read_sensor(sensor: Sensor) -> ReadSensorModel:
     readout = await sensor.read_sensor()
 

apps/rasptherm-backend/rasptherm_backend/types/sensor.py

@@ -0,0 +1,7 @@
+from typing import Protocol
+
+from rasptherm_sensor.types import SensorReadout
+
+
+class Sensor(Protocol):
+    async def read_sensor(self) -> SensorReadout: ...

apps/rasptherm-backend/rasptherm_backend/utils/sensor.py

@@ -0,0 +1,31 @@
+from collections.abc import Awaitable, Callable
+from functools import wraps
+from typing import TypeVar
+
+from fastapi import HTTPException, status
+from grpc import StatusCode  # type: ignore
+from grpc.aio import AioRpcError  # type: ignore
+
+from rasptherm_backend.types.sensor import Sensor
+
+_SensorOutput = TypeVar("_SensorOutput")
+_SensorFunc = Callable[[Sensor], Awaitable[_SensorOutput]]
+
+
+def sensor_not_available_handling(
+    sensor_func: _SensorFunc[_SensorOutput],
+) -> _SensorFunc[_SensorOutput]:
+    @wraps(sensor_func)
+    async def handle_sensor_not_awailable(sensor: Sensor) -> _SensorOutput:
+        try:
+            return await sensor_func(sensor)
+        except AioRpcError as rpc_exception:
+            if rpc_exception.code() != StatusCode.UNAVAILABLE:
+                raise rpc_exception
+
+            raise HTTPException(
+                status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+                detail={"msg": "The requested sensor is currently not available"},
+            )
+
+    return handle_sensor_not_awailable

apps/rasptherm-backend/tests/routers/test_sensor.py

@@ -4,6 +4,8 @@
 import pytest
 from fastapi import FastAPI, status
 from fastapi.testclient import TestClient
+from grpc import StatusCode  # type: ignore
+from grpc.aio import AioRpcError  # type: ignore
 from rasptherm_sensor.types import SensorReadout
 
 from rasptherm_backend.models.sensor import ReadSensorModel
@@ -18,6 +20,12 @@ def test_read_sensor(client: TestClient, expected_readout: ReadSensorModel) -> N
     assert response.json() == expected_readout.model_dump(mode="json", by_alias=True)
 
 
+@pytest.mark.usefixtures("override_get_sensor_with_not_available_sensor")
+def test_read_sensor_service_unavailable(client: TestClient) -> None:
+    response = client.get("/sensor/read")
+    assert response.status_code == status.HTTP_503_SERVICE_UNAVAILABLE
+
+
 class FakeSensor:
     def __init__(self, readout: ReadSensorModel) -> None:
         self._readout = readout
@@ -30,6 +38,15 @@ async def read_sensor(self) -> SensorReadout:
         )
 
 
+class FakeSensorNotAvailable:
+    async def read_sensor(self) -> SensorReadout:
+        raise AioRpcError(
+            code=StatusCode.UNAVAILABLE,
+            initial_metadata=None,
+            trailing_metadata=None,
+        )
+
+
 @pytest.fixture
 def expected_readout() -> ReadSensorModel:
     return ReadSensorModel(
@@ -48,3 +65,12 @@ async def get_fake_sensor() -> AsyncIterator[FakeSensor]:
 
     with override_dependency(app, get_sensor, get_fake_sensor):
         yield
+
+
+@pytest.fixture
+def override_get_sensor_with_not_available_sensor(app: FastAPI) -> Iterator[None]:
+    async def get_fake_sensor() -> AsyncIterator[FakeSensorNotAvailable]:
+        yield FakeSensorNotAvailable()
+
+    with override_dependency(app, get_sensor, get_fake_sensor):
+        yield