Remove KedroSession activate/deactivate mechanism

RELEASE.md

@@ -22,6 +22,7 @@
 * Introduced `after_command_run` CLI hook.
 * Update sections on visualisation, namespacing, and experiment tracking in the spaceflight tutorial to correspond to the complete spaceflights starter.
 * Fixed `Jinja2` syntax loading with `TemplatedConfigLoader` using `globals.yml`.
+* Removed global `_active_session`, `_activate_session` and `_deactivate_session`. Plugins that need to access objects such as the config loader should now do so through `context` in the new `after_context_created` hook.
 
 ## Upcoming deprecations for Kedro 0.19.0
 

kedro/extras/extensions/ipython.py

@@ -44,7 +44,6 @@ def reload_kedro(
     from kedro.framework.cli import load_entry_points
     from kedro.framework.project import configure_project, pipelines
     from kedro.framework.session import KedroSession
-    from kedro.framework.session.session import _activate_session
     from kedro.framework.startup import bootstrap_project
 
     # If a path is provided, set it as default for subsequent calls
@@ -63,7 +62,6 @@ def reload_kedro(
     session = KedroSession.create(
         metadata.package_name, default_project_path, env=env, extra_params=extra_params
     )
-    _activate_session(session, force=True)
     logging.debug("Loading the context from %s", default_project_path)
     context = session.load_context()
     catalog = context.catalog

kedro/framework/session/session.py

@@ -28,24 +28,6 @@
 from kedro.io.core import generate_timestamp
 from kedro.runner import AbstractRunner, SequentialRunner
 
-_active_session = None
-
-
-def _activate_session(session: "KedroSession", force: bool = False) -> None:
-    global _active_session
-
-    if _active_session and not force and session is not _active_session:
-        raise RuntimeError(
-            "Cannot activate the session as another active session already exists."
-        )
-
-    _active_session = session
-
-
-def _deactivate_session() -> None:
-    global _active_session
-    _active_session = None
-
 
 def _describe_git(project_path: Path) -> Dict[str, Dict[str, Any]]:
     project_path = str(project_path)
@@ -282,12 +264,7 @@ def close(self):
         if self.save_on_close:
             self._store.save()
 
-        if _active_session is self:
-            _deactivate_session()
-
     def __enter__(self):
-        if _active_session is not self:
-            _activate_session(self)
         return self
 
     def __exit__(self, exc_type, exc_value, tb_):

tests/extras/extensions/test_ipython.py

@@ -2,7 +2,6 @@
 import pytest
 
 from kedro.extras.extensions.ipython import load_ipython_extension, reload_kedro
-from kedro.framework.session.session import _deactivate_session
 from kedro.framework.startup import ProjectMetadata
 from kedro.pipeline import Pipeline
 
@@ -23,7 +22,6 @@ def mocked_logging(mocker):
 @pytest.fixture(autouse=True)
 def cleanup_session():
     yield
-    _deactivate_session()
 
 
 @pytest.fixture()

tests/framework/session/test_session.py

@@ -17,7 +17,6 @@
     _HasSharedParentClassValidator,
     _IsSubclassValidator,
     _ProjectSettings,
-    configure_project,
 )
 from kedro.framework.session import KedroSession
 from kedro.framework.session.store import BaseSessionStore, ShelveStore
@@ -285,6 +284,12 @@ def test_create(
         assert session.load_context() is mock_context_class.return_value
         assert isinstance(session._get_config_loader(), ConfigLoader)
 
+    @pytest.mark.usefixtures("mock_settings")
+    def test_create_multiple_sessions(self, fake_project, mock_package_name):
+        with KedroSession.create(mock_package_name, fake_project):
+            with KedroSession.create(mock_package_name, fake_project):
+                ...
+
     @pytest.mark.usefixtures("mock_settings_context_class")
     def test_create_no_env_extra_params(
         self,
@@ -519,19 +524,6 @@ def test_log_error(self, fake_project, mock_package_name):
             "raise FakeException" in tb_line for tb_line in exception["traceback"]
         )
 
-    @pytest.mark.usefixtures("mock_settings")
-    def test_nested_sessions(self, fake_project, mock_package_name):
-        configure_project(mock_package_name)
-        session1 = KedroSession.create(mock_package_name, fake_project)
-        session2 = KedroSession.create(mock_package_name, fake_project)
-
-        with session1:
-            pattern = (
-                "Cannot activate the session as another active session already exists"
-            )
-            with pytest.raises(RuntimeError, match=pattern), session2:
-                pass  # pragma: no cover
-
     @pytest.mark.usefixtures("mock_settings_context_class")
     @pytest.mark.parametrize("fake_pipeline_name", [None, _FAKE_PIPELINE_NAME])
     def test_run(