Add multi-tenancy support for Postgres (#383)

This PR addresses 382 and adds naive support for multi-tenancy with a "MULTITENANCY" flag.

Domain context can now be initialized witn arbitrary attributes. In our case, we will
be setting MULTITENANCY to True.

Improvements to be done:
- a better way to supply database info in a multi-tenancy use case
- reset database connection to default after execution

src/protean/adapters/repository/__init__.py

@@ -7,6 +7,7 @@
 
 from protean.core.repository import BaseRepository, repository_factory
 from protean.exceptions import ConfigurationError
+from protean.globals import g
 from protean.utils import fully_qualified_name
 
 logger = logging.getLogger(__name__)
@@ -119,7 +120,9 @@ def _initialize(self):
 
     def get_connection(self, provider_name="default"):
         """Fetch connection from Provider"""
-        if self._providers is None:
+        if (
+            hasattr(g, "MULTITENANCY") and g.MULTITENANCY is True
+        ) or self._providers is None:
             self._initialize()
 
         try:
@@ -129,7 +132,9 @@ def get_connection(self, provider_name="default"):
 
     def repository_for(self, aggregate_cls):
         """Retrieve a Repository registered for the Aggregate"""
-        if self._providers is None:
+        if (
+            hasattr(g, "MULTITENANCY") and g.MULTITENANCY is True
+        ) or self._providers is None:
             self._initialize()
 
         provider_name = aggregate_cls.meta_.provider

src/protean/domain/__init__.py

@@ -261,7 +261,7 @@ def make_config(self, instance_relative=False):
         defaults["DEBUG"] = get_debug_flag()
         return self.config_class(root_path, defaults)
 
-    def domain_context(self):
+    def domain_context(self, **kwargs):
         """Create an :class:`~protean.context.DomainContext`. Use as a ``with``
         block to push the context, which will make :data:`current_domain`
         point at this domain.
@@ -271,7 +271,7 @@ def domain_context(self):
             with domain.domain_context():
                 init_db()
         """
-        return DomainContext(self)
+        return DomainContext(self, **kwargs)
 
     def teardown_domain_context(self, f):
         """Registers a function to be called when the domain context
@@ -754,7 +754,7 @@ def handlers_for(self, event: BaseEvent) -> List[BaseEventHandler]:
     # Repository Functionality #
     ############################
 
-    @lru_cache(maxsize=None)
+    # FIXME Optimize calls to this method with cache, but also with support for Multitenancy
     def repository_for(self, aggregate_cls):
         if aggregate_cls.element_type == DomainObjects.EVENT_SOURCED_AGGREGATE:
             return self.event_store.repository_for(aggregate_cls)

src/protean/domain/context.py

@@ -75,10 +75,14 @@ class DomainContext(object):
     to the current thread or greenlet.
     """
 
-    def __init__(self, domain):
+    def __init__(self, domain, **kwargs):
         self.domain = domain
         self.g = domain.domain_context_globals_class()
 
+        # Set any additional kwargs as attributes in globals
+        for kw in kwargs.items():
+            setattr(self.g, *kw)
+
         # Use a basic "refcount" to track number of domain contexts
         self._ref_count = 0
 

tests/adapters/repository/sqlalchemy_repo/postgresql/test_schema_switch.py

@@ -0,0 +1,26 @@
+import pytest
+
+from protean.globals import current_domain
+
+from .elements import Person
+
+
+# @pytest.mark.postgresql
+class TestSchemaSwitch:
+    @pytest.fixture(autouse=True)
+    def register_elements(self, test_domain):
+        test_domain.register(Person)
+
+    def test_schema_switch(self, test_domain):
+        repo = test_domain.repository_for(Person)
+        assert repo._provider._metadata.schema == "public"
+
+        with current_domain.domain_context(MULTITENANCY=True):
+            current_domain.config["DATABASES"]["default"]["SCHEMA"] = "private"
+
+            repo1 = current_domain.repository_for(Person)
+            assert repo1._provider._metadata.schema == "private"
+
+        # FIXME Reset the database info to default outside the context
+        # repo2 = test_domain.repository_for(Person)
+        # assert repo2._provider._metadata.schema == "public"

tests/context/tests.py

@@ -137,3 +137,17 @@ def __init__(self):
         test_domain.domain_context_globals_class = CustomRequestGlobals
         with test_domain.domain_context():
             assert g.spam == "eggs"
+
+    # Test passing kwargs to domain context during activation
+    def test_domain_context_kwargs(self, test_domain):
+        with test_domain.domain_context(foo="bar"):
+            assert g.foo == "bar"
+
+        assert "foo" not in g
+
+    # Test global attributes are not shared between domain contexts
+    def test_domain_context_globals_not_shared(self, test_domain):
+        with test_domain.domain_context(foo="bar"):
+            assert g.foo == "bar"
+        with test_domain.domain_context(foo="baz"):
+            assert g.foo == "baz"