chore: enable ModuleWatchdog globally (#4098)

## Description

This change installs an instance of the `ModuleWatchdog` for registering module import hooks.

## Checklist
- [x] Title must conform to [conventional commit](https://github.com/conventional-changelog/commitlint/tree/master/%40commitlint/config-conventional).
- [x] Add additional sections for `feat` and `fix` pull requests.
- [x] Ensure tests are passing for affected code.
- [x] [Library documentation](https://github.com/DataDog/dd-trace-py/tree/1.x/docs) and/or [Datadog's documentation site](https://github.com/DataDog/documentation/) is updated. Link to doc PR in description.

## Reviewer Checklist
- [ ] Title is accurate.
- [ ] Description motivates each change.
- [ ] No unnecessary changes were introduced in this PR.
- [ ] PR cannot be broken up into smaller PRs.
- [ ] Avoid breaking [API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces) changes unless absolutely necessary.
- [ ] Tests provided or description of manual testing performed is included in the code or PR.
- [x] Release note has been added for fixes and features, or else `changelog/no-changelog` label added.
- [ ] All relevant GitHub issues are correctly linked.
- [ ] Backports are identified and tagged with Mergifyio.
- [ ] Add to milestone.

ddtrace/__init__.py

@@ -1,4 +1,9 @@
-from ._logger import configure_ddtrace_logger
+from ddtrace.internal.module import ModuleWatchdog
+
+
+ModuleWatchdog.install()
+
+from ._logger import configure_ddtrace_logger  # noqa: E402
 
 
 # configure ddtrace logger before other modules log

tests/internal/test_module.py

@@ -9,6 +9,22 @@
 import tests.test_module
 
 
+@pytest.fixture(autouse=True, scope="module")
+def ensure_no_module_watchdog():
+    # DEV: The library might use the ModuleWatchdog and install it at a very
+    # early stage. This fixture ensures that the watchdog is not installed
+    # before the tests start.
+    was_installed = ModuleWatchdog.is_installed()
+    if was_installed:
+        ModuleWatchdog.uninstall()
+
+    try:
+        yield
+    finally:
+        if was_installed:
+            ModuleWatchdog.install()
+
+
 @pytest.fixture
 def module_watchdog():
     ModuleWatchdog.install()
@@ -65,8 +81,6 @@ def test_import_origin_hook_for_module_not_yet_imported():
     path = os.getenv("MODULE_ORIGIN")
     hook = mock.Mock()
 
-    ModuleWatchdog.install()
-
     ModuleWatchdog.register_origin_hook(path, hook)
 
     hook.assert_not_called()
@@ -100,8 +114,6 @@ def test_import_module_hook_for_module_not_yet_imported():
     name = "tests.test_module"
     hook = mock.Mock()
 
-    ModuleWatchdog.install()
-
     ModuleWatchdog.register_module_hook(name, hook)
 
     hook.assert_not_called()
@@ -136,8 +148,6 @@ def test_module_deleted():
     path = os.getenv("MODULE_ORIGIN")
     hook = mock.Mock()
 
-    ModuleWatchdog.install()
-
     ModuleWatchdog.register_origin_hook(path, hook)
     ModuleWatchdog.register_module_hook(name, hook)
 
@@ -327,3 +337,5 @@ def test_module_watchdog_dict_shallow_copy():
 
     # Ensure that they match
     assert original_modules == new_modules
+
+    ModuleWatchdog.uninstall()

tests/profiling/collector/test_threading.py

@@ -72,7 +72,7 @@ def test_lock_acquire_events():
     # It's called through pytest so I'm sure it's gonna be that long, right?
     assert len(event.frames) > 3
     assert event.nframes > 3
-    assert event.frames[0] == (__file__, 65, "test_lock_acquire_events")
+    assert event.frames[0] == (__file__.replace(".pyc", ".py"), 65, "test_lock_acquire_events")
     assert event.sampling_pct == 100
 
 
@@ -187,7 +187,7 @@ def test_lock_release_events():
     # It's called through pytest so I'm sure it's gonna be that long, right?
     assert len(event.frames) > 3
     assert event.nframes > 3
-    assert event.frames[0] == (__file__, 180, "test_lock_release_events")
+    assert event.frames[0] == (__file__.replace(".pyc", ".py"), 180, "test_lock_release_events")
     assert event.sampling_pct == 100
 
 
@@ -217,7 +217,7 @@ def play_with_lock():
             # It's called through pytest so I'm sure it's gonna be that long, right?
             assert len(event.frames) > 3
             assert event.nframes > 3
-            assert event.frames[0] == (__file__, 200, "play_with_lock")
+            assert event.frames[0] == (__file__.replace(".pyc", ".py"), 200, "play_with_lock")
             assert event.sampling_pct == 100
             assert event.task_id == t.ident
             assert event.task_name == "foobar"
@@ -234,7 +234,7 @@ def play_with_lock():
             # It's called through pytest so I'm sure it's gonna be that long, right?
             assert len(event.frames) > 3
             assert event.nframes > 3
-            assert event.frames[0] == (__file__, 201, "play_with_lock")
+            assert event.frames[0] == (__file__.replace(".pyc", ".py"), 201, "play_with_lock")
             assert event.sampling_pct == 100
             assert event.task_id == t.ident
             assert event.task_name == "foobar"

tests/profiling/collector/test_traceback.py

@@ -14,11 +14,9 @@ def test_check_traceback_to_frames():
         exc_type, exc_value, traceback = sys.exc_info()
     frames, nframes = _traceback.traceback_to_frames(traceback, 10)
     assert nframes == 2
+
+    this_file = __file__.replace(".pyc", ".py")
     assert frames == [
-        (__file__, 7, "_x"),
-        (
-            __file__,
-            15,
-            "test_check_traceback_to_frames",
-        ),
+        (this_file, 7, "_x"),
+        (this_file, 15, "test_check_traceback_to_frames"),
     ]