#2114 repeating query in django view (#2158)

* avoid making extensive queries by overriding queryset cache

* move variable transformation to transform encoding util

* handle django not installed, clearer failed query code

* Cleanup pr

* Run pre-commit

* Update elasticapm/utils/encoding.py

---------

Co-authored-by: p.okapiec <[email protected]>
Co-authored-by: Riccardo Magliocchetti <[email protected]>

Author: 3 people

elasticapm/utils/encoding.py

@@ -36,6 +36,11 @@
 import uuid
 from decimal import Decimal
 
+try:
+    from django.db.models import QuerySet as DjangoQuerySet
+except ImportError:
+    DjangoQuerySet = None
+
 from elasticapm.conf.constants import KEYWORD_MAX_LENGTH, LABEL_RE, LABEL_TYPES, LONG_FIELD_MAX_LENGTH
 
 PROTECTED_TYPES = (int, type(None), float, Decimal, datetime.datetime, datetime.date, datetime.time)
@@ -144,6 +149,14 @@ class value_type(list):
         ret = float(value)
     elif isinstance(value, int):
         ret = int(value)
+    elif (
+        DjangoQuerySet is not None
+        and isinstance(value, DjangoQuerySet)
+        and getattr(value, "_result_cache", True) is None
+    ):
+        # if we have a Django QuerySet a None result cache it may mean that the underlying query failed
+        # so represent it as unevaluated instead of retrying the query again
+        ret = "<%s `unevaluated`>" % (value.__class__.__name__)
     elif value is not None:
         try:
             ret = transform(repr(value))

tests/contrib/django/django_tests.py

@@ -1250,6 +1250,23 @@ def test_capture_post_errors_dict(client, django_elasticapm_client):
         assert error["context"]["request"]["body"] == "[REDACTED]"
 
 
+@pytest.mark.parametrize(
+    "django_elasticapm_client",
+    [{"capture_body": "errors"}, {"capture_body": "transactions"}, {"capture_body": "all"}, {"capture_body": "off"}],
+    indirect=True,
+)
+def test_capture_django_orm_timeout_error(client, django_elasticapm_client):
+    with pytest.raises(DatabaseError):
+        client.get(reverse("elasticapm-django-orm-exc"))
+
+    errors = django_elasticapm_client.events[ERROR]
+    if django_elasticapm_client.config.capture_body in (constants.ERROR, "all"):
+        stacktrace = errors[0]["exception"]["stacktrace"]
+        frames = [frame for frame in stacktrace if frame["function"] == "django_queryset_error"]
+        qs_var = frames[0]["vars"]["qs"]
+        assert qs_var == "<CustomQuerySet `unevaluated`>"
+
+
 def test_capture_body_config_is_dynamic_for_errors(client, django_elasticapm_client):
     django_elasticapm_client.config.update(version="1", capture_body="all")
     with pytest.raises(MyException):

tests/contrib/django/testapp/urls.py

@@ -62,6 +62,7 @@ def handler500(request):
     re_path(r"^trigger-500-ioerror$", views.raise_ioerror, name="elasticapm-raise-ioerror"),
     re_path(r"^trigger-500-decorated$", views.decorated_raise_exc, name="elasticapm-raise-exc-decor"),
     re_path(r"^trigger-500-django$", views.django_exc, name="elasticapm-django-exc"),
+    re_path(r"^trigger-500-django-orm-exc$", views.django_queryset_error, name="elasticapm-django-orm-exc"),
     re_path(r"^trigger-500-template$", views.template_exc, name="elasticapm-template-exc"),
     re_path(r"^trigger-500-log-request$", views.logging_request_exc, name="elasticapm-log-request-exc"),
     re_path(r"^streaming$", views.streaming_view, name="elasticapm-streaming-view"),

tests/contrib/django/testapp/views.py

@@ -34,6 +34,8 @@
 import time
 
 from django.contrib.auth.models import User
+from django.db import DatabaseError
+from django.db.models import QuerySet
 from django.http import HttpResponse, StreamingHttpResponse
 from django.shortcuts import get_object_or_404, render
 from django.views import View
@@ -70,6 +72,20 @@ def django_exc(request):
     return get_object_or_404(MyException, pk=1)
 
 
+def django_queryset_error(request):
+    """Simulation of django ORM timeout"""
+
+    class CustomQuerySet(QuerySet):
+        def all(self):
+            raise DatabaseError()
+
+        def __repr__(self) -> str:
+            return str(self._result_cache)
+
+    qs = CustomQuerySet()
+    list(qs.all())
+
+
 def raise_exc(request):
     raise MyException(request.GET.get("message", "view exception"))