Handle network errors via translation in a DRF custom exception handler

twitch_hdt_ebs/exceptions.py

@@ -1,5 +1,10 @@
+import logging
+
+import requests
+from hearthsim.instrumentation.django_influxdb import write_point
 from rest_framework import status
 from rest_framework.exceptions import APIException
+from rest_framework.views import exception_handler
 
 
 class TwitchAPITimeout(APIException):
@@ -20,3 +25,38 @@ class BadGateway(APIException):
 class BadTwitchResponse(BadGateway):
 	default_detail = "Twitch returned an invalid response."
 	default_code = "bad_twitch_response"
+
+
+def untapped_django_exception_handler(exc, context):
+	"""A Django REST Framework "custom exception handler" for translating additional types.
+
+	This implementation attempts to convert upstream exception types corresponding to HTTP
+	502 (Bad gateway) and HTTP 504 (Gateway timeout) before delegating to the default
+	exception handler implementation.
+
+	See also
+	https://www.django-rest-framework.org/api-guide/exceptions/#custom-exception-handling
+
+	:param exc:
+	:param context:
+	"""
+
+	if isinstance(exc, requests.Timeout):
+		effective_exc = TwitchAPITimeout()
+	elif (
+		isinstance(exc, requests.ConnectionError) or
+		isinstance(exc, requests.HTTPError)
+	):
+		effective_exc = BadGateway()
+	else:
+		effective_exc = exc
+
+	detail = getattr(exc, "detail", {})
+
+	logger = logging.getLogger("twitch_hdt_ebs")
+	logger.error("Got exception %r, detail=%r", exc, detail)
+
+	if detail and isinstance(detail, dict):
+		write_point("api_error", {"count": 1}, error=detail.get("error", "unknown"))
+
+	return exception_handler(effective_exc, context)

twitch_hdt_ebs/settings.py

@@ -138,7 +138,7 @@ def get_deployment_uuid():
 # Disable DRF browsable API (it requires templates to be setup)
 REST_FRAMEWORK = {
 	"DEFAULT_RENDERER_CLASSES": ("rest_framework.renderers.JSONRenderer", ),
-	"EXCEPTION_HANDLER": "twitch_hdt_ebs.views.exception_handler",
+	"EXCEPTION_HANDLER": "twitch_hdt_ebs.exceptions.untapped_django_exception_handler",
 }
 
 # DRF CORS handling

twitch_hdt_ebs/views.py

@@ -1,7 +1,6 @@
 import base64
 import hashlib
 import json
-import logging
 import string
 from typing import Any, Dict, List, Optional
 
@@ -520,18 +519,3 @@ def get(self, request, user_id) -> Response:
 class PingView(View):
 	def get(self, request):
 		return HttpResponse("OK", content_type="text/plain")
-
-
-def exception_handler(exc, context):
-	from rest_framework.views import exception_handler as original_handler
-
-	response = original_handler(exc, context)
-	detail = getattr(exc, "detail", {})
-
-	logger = logging.getLogger("twitch_hdt_ebs")
-	logger.error("Got exception %r, detail=%r", exc, detail)
-
-	if detail and isinstance(detail, dict):
-		write_point("api_error", {"count": 1}, error=detail.get("error", "unknown"))
-
-	return response