Use FastAPI dependency overrides

Instead of manually setting a global variable to configure the test
server's Butler, use FastAPI's dependency injection framework.

python/lsst/daf/butler/remote_butler/server/__init__.py

@@ -25,4 +25,5 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from ._server import app
+from ._factory import Factory
+from ._server import app, factory_dependency

python/lsst/daf/butler/remote_butler/server/_factory.py

@@ -0,0 +1,36 @@
+# This file is part of daf_butler.
+#
+# Developed for the LSST Data Management System.
+# This product includes software developed by the LSST Project
+# (http://www.lsst.org).
+# See the COPYRIGHT file at the top-level directory of this distribution
+# for details of code ownership.
+#
+# This software is dual licensed under the GNU General Public License and also
+# under a 3-clause BSD license. Recipients may choose which of these licenses
+# to use; please see the files gpl-3.0.txt and/or bsd_license.txt,
+# respectively.  If you choose the GPL option then the following text applies
+# (but note that there is still no warranty even if you opt for BSD instead):
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from lsst.daf.butler import Butler
+
+
+class Factory:
+    def __init__(self, *, butler: Butler):
+        self._butler = butler
+
+    def create_butler(self) -> Butler:
+        return self._butler

python/lsst/daf/butler/remote_butler/server/_server.py

@@ -30,12 +30,15 @@
 __all__ = ()
 
 import logging
+from functools import cache
 from typing import Any
 
 from fastapi import Depends, FastAPI
 from fastapi.middleware.gzip import GZipMiddleware
 from lsst.daf.butler import Butler
 
+from ._factory import Factory
+
 BUTLER_ROOT = "ci_hsc_gen3/DATA"
 
 log = logging.getLogger("excalibur")
@@ -44,28 +47,13 @@
 app.add_middleware(GZipMiddleware, minimum_size=1000)
 
 
-GLOBAL_READWRITE_BUTLER: Butler | None = None
-GLOBAL_READONLY_BUTLER: Butler | None = None
-
-
-def _make_global_butler() -> None:
-    global GLOBAL_READONLY_BUTLER, GLOBAL_READWRITE_BUTLER
-    if GLOBAL_READONLY_BUTLER is None:
-        GLOBAL_READONLY_BUTLER = Butler.from_config(BUTLER_ROOT, writeable=False)
-    if GLOBAL_READWRITE_BUTLER is None:
-        GLOBAL_READWRITE_BUTLER = Butler.from_config(BUTLER_ROOT, writeable=True)
-
-
-def butler_readonly_dependency() -> Butler:
-    """Return global read-only butler."""
-    _make_global_butler()
-    return Butler.from_config(butler=GLOBAL_READONLY_BUTLER)
+@cache
+def _make_global_butler() -> Butler:
+    return Butler.from_config(BUTLER_ROOT)
 
 
-def butler_readwrite_dependency() -> Butler:
-    """Return read-write butler."""
-    _make_global_butler()
-    return Butler.from_config(butler=GLOBAL_READWRITE_BUTLER)
+def factory_dependency() -> Factory:
+    return Factory(butler=_make_global_butler())
 
 
 @app.get("/butler/")
@@ -75,6 +63,7 @@ def read_root() -> str:
 
 
 @app.get("/butler/v1/universe", response_model=dict[str, Any])
-def get_dimension_universe(butler: Butler = Depends(butler_readonly_dependency)) -> dict[str, Any]:
+def get_dimension_universe(factory: Factory = Depends(factory_dependency)) -> dict[str, Any]:
     """Allow remote client to get dimensions definition."""
+    butler = factory.create_butler()
     return butler.dimensions.dimensionConfig.toDict()

tests/test_server.py

@@ -29,17 +29,15 @@
 import unittest
 
 try:
-    import lsst.daf.butler.remote_butler.server._server
-
     # Failing to import any of these should disable the tests.
     from fastapi.testclient import TestClient
     from lsst.daf.butler.remote_butler import RemoteButler
-    from lsst.daf.butler.remote_butler.server._server import app
+    from lsst.daf.butler.remote_butler.server import Factory, app, factory_dependency
 except ImportError:
     TestClient = None
     app = None
 
-from lsst.daf.butler import CollectionType
+from lsst.daf.butler import Butler
 from lsst.daf.butler.tests.utils import MetricTestRepo, makeTestTempDir, removeTestTempDir
 
 TESTDIR = os.path.abspath(os.path.dirname(__file__))
@@ -67,21 +65,21 @@ def setUpClass(cls):
         # First create a butler and populate it.
         cls.root = makeTestTempDir(TESTDIR)
         cls.repo = MetricTestRepo(root=cls.root, configFile=os.path.join(TESTDIR, "config/basic/butler.yaml"))
+        # Override the server's Butler initialization to point at our test repo
+        server_butler = Butler.from_config(cls.root)
 
-        # Add a collection chain.
-        cls.repo.butler.registry.registerCollection("chain", CollectionType.CHAINED)
-        cls.repo.butler.registry.setCollectionChain("chain", ["ingest"])
+        def create_factory_dependency():
+            return Factory(butler=server_butler)
 
-        # Globally change where the server thinks its butler repository
-        # is located. This will prevent any other server tests and is
-        # not a long term fix.
-        lsst.daf.butler.remote_butler.server._server.BUTLER_ROOT = cls.root
-        cls.client = TestClient(app)
+        app.dependency_overrides[factory_dependency] = create_factory_dependency
 
+        # Set up the RemoteButler that will connect to the server
+        cls.client = TestClient(app)
         cls.butler = _make_remote_butler(cls.client)
 
     @classmethod
     def tearDownClass(cls):
+        del app.dependency_overrides[factory_dependency]
         removeTestTempDir(cls.root)
 
     def test_simple(self):