fix: Data leak in ThreadingIntegration between threads

sentry_sdk/integrations/threading.py

@@ -1,4 +1,5 @@
 import sys
+import warnings
 from functools import wraps
 from threading import Thread, current_thread
 
@@ -57,8 +58,36 @@ def sentry_start(self, *a, **kw):
                 return old_start(self, *a, **kw)
 
             if integration.propagate_scope:
-                isolation_scope = sentry_sdk.get_isolation_scope()
-                current_scope = sentry_sdk.get_current_scope()
+                try:
+                    from django import VERSION as django_version  # noqa: N811
+                    import channels  # type: ignore[import-not-found]
+
+                    channels_version = channels.__version__
+                except ImportError:
+                    django_version = None
+                    channels_version = None
+
+                if (
+                    sys.version_info <= (3, 8)
+                    and channels_version is not None
+                    and channels_version < "4.0.0"
+                    and django_version is not None
+                    and django_version >= (3, 0)
+                    and django_version < (4, 0)
+                ):
+                    warnings.warn(
+                        "There is a known issue with Django channels 2.x and 3.x when using Python 3.8 or older. "
+                        "(Async support is emulated using threads and some Sentry data may be leaked between those threads.) "
+                        "Please either upgrade to Django channels 4.0+, use Django's async features "
+                        "available in Django 3.1+ instead of Django channels, or upgrade to Python 3.9+.",
+                        stacklevel=2,
+                    )
+                    isolation_scope = sentry_sdk.get_isolation_scope()
+                    current_scope = sentry_sdk.get_current_scope()
+
+                else:
+                    isolation_scope = sentry_sdk.get_isolation_scope().fork()
+                    current_scope = sentry_sdk.get_current_scope().fork()
             else:
                 isolation_scope = None
                 current_scope = None

tests/integrations/django/asgi/test_asgi.py

@@ -38,9 +38,18 @@ async def test_basic(sentry_init, capture_events, application):
 
     events = capture_events()
 
-    comm = HttpCommunicator(application, "GET", "/view-exc?test=query")
-    response = await comm.get_response()
-    await comm.wait()
+    if sys.version_info <= (3, 8):
+        # We emit a UserWarning for channels 2.x and 3.x on Python 3.8 and older
+        # because the async support was not really good back then and there is a known issue.
+        # See the TreadingIntegration for details.
+        with pytest.warns(UserWarning):
+            comm = HttpCommunicator(application, "GET", "/view-exc?test=query")
+            response = await comm.get_response()
+            await comm.wait()
+    else:
+        comm = HttpCommunicator(application, "GET", "/view-exc?test=query")
+        response = await comm.get_response()
+        await comm.wait()
 
     assert response["status"] == 500
 

tests/integrations/threading/test_threading.py

@@ -1,5 +1,6 @@
 import gc
 from concurrent import futures
+from textwrap import dedent
 from threading import Thread
 
 import pytest
@@ -172,3 +173,103 @@ def target():
     assert Thread.run.__qualname__ == original_run.__qualname__
     assert t.run.__name__ == "run"
     assert t.run.__qualname__ == original_run.__qualname__
+
+
+@pytest.mark.parametrize(
+    "propagate_scope",
+    (True, False),
+    ids=["propagate_scope=True", "propagate_scope=False"],
+)
+def test_scope_data_not_leaked_in_threads(sentry_init, propagate_scope):
+    sentry_init(
+        integrations=[ThreadingIntegration(propagate_scope=propagate_scope)],
+    )
+
+    sentry_sdk.set_tag("initial_tag", "initial_value")
+    initial_iso_scope = sentry_sdk.get_isolation_scope()
+
+    def do_some_work():
+        # check if we have the initial scope data propagated into the thread
+        if propagate_scope:
+            assert sentry_sdk.get_isolation_scope()._tags == {
+                "initial_tag": "initial_value"
+            }
+        else:
+            assert sentry_sdk.get_isolation_scope()._tags == {}
+
+        # change data in isolation scope in thread
+        sentry_sdk.set_tag("thread_tag", "thread_value")
+
+    t = Thread(target=do_some_work)
+    t.start()
+    t.join()
+
+    # check if the initial scope data is not modified by the started thread
+    assert initial_iso_scope._tags == {
+        "initial_tag": "initial_value"
+    }, "The isolation scope in the main thread should not be modified by the started thread."
+
+
+@pytest.mark.parametrize(
+    "propagate_scope",
+    (True, False),
+    ids=["propagate_scope=True", "propagate_scope=False"],
+)
+def test_spans_from_multiple_threads(
+    sentry_init, capture_events, render_span_tree, propagate_scope
+):
+    sentry_init(
+        traces_sample_rate=1.0,
+        integrations=[ThreadingIntegration(propagate_scope=propagate_scope)],
+    )
+    events = capture_events()
+
+    def do_some_work(number):
+        with sentry_sdk.start_span(
+            op=f"inner-run-{number}", name=f"Thread: child-{number}"
+        ):
+            pass
+
+    threads = []
+
+    with sentry_sdk.start_transaction(op="outer-trx"):
+        for number in range(5):
+            with sentry_sdk.start_span(
+                op=f"outer-submit-{number}", name="Thread: main"
+            ):
+                t = Thread(target=do_some_work, args=(number,))
+                t.start()
+                threads.append(t)
+
+        for t in threads:
+            t.join()
+
+    (event,) = events
+    if propagate_scope:
+        assert render_span_tree(event) == dedent(
+            """\
+            - op="outer-trx": description=null
+              - op="outer-submit-0": description="Thread: main"
+                - op="inner-run-0": description="Thread: child-0"
+              - op="outer-submit-1": description="Thread: main"
+                - op="inner-run-1": description="Thread: child-1"
+              - op="outer-submit-2": description="Thread: main"
+                - op="inner-run-2": description="Thread: child-2"
+              - op="outer-submit-3": description="Thread: main"
+                - op="inner-run-3": description="Thread: child-3"
+              - op="outer-submit-4": description="Thread: main"
+                - op="inner-run-4": description="Thread: child-4"\
+"""
+        )
+
+    elif not propagate_scope:
+        assert render_span_tree(event) == dedent(
+            """\
+            - op="outer-trx": description=null
+              - op="outer-submit-0": description="Thread: main"
+              - op="outer-submit-1": description="Thread: main"
+              - op="outer-submit-2": description="Thread: main"
+              - op="outer-submit-3": description="Thread: main"
+              - op="outer-submit-4": description="Thread: main"\
+"""
+        )