Fix(fabric): Ensure that Fabric connections do not try to use a catalog once it's been dropped

sqlmesh/core/engine_adapter/fabric.py

@@ -121,10 +121,19 @@ def _create_catalog(self, catalog_name: exp.Identifier) -> None:
     def _drop_catalog(self, catalog_name: exp.Identifier) -> None:
         """Drop a catalog (warehouse) in Microsoft Fabric via REST API."""
         warehouse_name = catalog_name.sql(dialect=self.dialect, identify=False)
+        current_catalog = self.get_current_catalog()
 
         logger.info(f"Deleting Fabric warehouse: {warehouse_name}")
         self.api_client.delete_warehouse(warehouse_name)
 
+        if warehouse_name == current_catalog:
+            # Somewhere around 2025-09-08, Fabric started validating the "Database=" connection argument and throwing 'Authentication failed' if the database doesnt exist
+            # In addition, set_current_catalog() is implemented using a threadlocal variable "target_catalog"
+            # So, when we drop a warehouse, and there are still threads with "target_catalog" set to reference it, any operations on those threads
+            # that use an either use an existing connection pointing to this warehouse or trigger a new connection
+            # will fail with an 'Authentication Failed' error unless we close all connections here, which also clears all the threadlocal data
+            self.close()
+
     def set_current_catalog(self, catalog_name: str) -> None:
         """
         Set the current catalog for Microsoft Fabric connections.

sqlmesh/utils/connection_pool.py

@@ -227,7 +227,8 @@ def close_all(self, exclude_calling_thread: bool = False) -> None:
                     self._thread_connections.pop(thread_id)
                     self._thread_cursors.pop(thread_id, None)
                     self._discard_transaction(thread_id)
-                self._thread_attributes.pop(thread_id, None)
+
+            self._thread_attributes.clear()
 
 
 class ThreadLocalSharedConnectionPool(_ThreadLocalBase):

tests/core/engine_adapter/integration/test_integration.py

@@ -3743,6 +3743,14 @@ def _set_config(gateway: str, config: Config) -> None:
         assert not md.tables
         assert not md.managed_tables
 
+    if ctx.dialect == "fabric":
+        # TestContext is using a different EngineAdapter instance / connection pool instance to the SQLMesh context
+        # When the SQLMesh context drops :snapshot_schema using its EngineAdapter, connections in TestContext are unaware
+        # and still have their threadlocal "target_catalog" attribute pointing to a catalog that no longer exists
+        # Trying to establish a connection to a nonexistant catalog produces an error, so we close all connections here
+        # to clear the threadlocal attributes
+        ctx.engine_adapter.close()
+
     md = ctx.get_metadata_results(snapshot_schema)
     assert not md.views
     assert not md.managed_tables

tests/core/engine_adapter/integration/test_integration_fabric.py

@@ -1,8 +1,12 @@
 import typing as t
+import threading
+import queue
 import pytest
 from pytest import FixtureRequest
 from sqlmesh.core.engine_adapter import FabricEngineAdapter
+from sqlmesh.utils.connection_pool import ThreadLocalConnectionPool
 from tests.core.engine_adapter.integration import TestContext
+from concurrent.futures import ThreadPoolExecutor
 
 from tests.core.engine_adapter.integration import (
     TestContext,
@@ -39,3 +43,75 @@ def test_create_drop_catalog(ctx: TestContext, engine_adapter: FabricEngineAdapt
     finally:
         # if doesnt exist, should be no-op, not error
         ctx.drop_catalog(catalog_name)
+
+
+def test_drop_catalog_clears_threadlocals_that_reference_it(
+    ctx: TestContext, engine_adapter: FabricEngineAdapter
+):
+    catalog_name = ctx.add_test_suffix("test_drop_catalog")
+    default_catalog = engine_adapter.get_current_catalog()
+
+    assert isinstance(engine_adapter._connection_pool, ThreadLocalConnectionPool)
+
+    # sets the connection attribute for this thread
+    engine_adapter.create_catalog(catalog_name)
+    assert engine_adapter._target_catalog is None
+    engine_adapter.set_current_catalog(catalog_name)
+    assert engine_adapter.get_current_catalog() == catalog_name
+    assert engine_adapter._target_catalog == catalog_name
+
+    lock = threading.RLock()
+
+    def _set_and_return_catalog_in_another_thread(
+        q: queue.Queue, engine_adapter: FabricEngineAdapter
+    ) -> t.Optional[str]:
+        q.put("thread_started")
+
+        assert engine_adapter.get_current_catalog() == default_catalog
+        assert engine_adapter._target_catalog is None
+
+        engine_adapter.set_current_catalog(catalog_name)
+        assert engine_adapter.get_current_catalog() == catalog_name
+        assert engine_adapter._target_catalog == catalog_name
+
+        q.put("catalog_set_in_thread")
+
+        # block this thread while we drop the catalog in the main test thread
+        lock.acquire()
+
+        # the current catalog should have been cleared from the threadlocal connection attributes
+        # when this catalog was dropped by the outer thread, causing it to fall back to the default catalog
+        try:
+            assert engine_adapter._target_catalog is None
+            return engine_adapter.get_current_catalog()
+        finally:
+            lock.release()
+
+    q: queue.Queue = queue.Queue()
+
+    with ThreadPoolExecutor() as executor:
+        lock.acquire()  # we have the lock, thread will be blocked until we release it
+
+        future = executor.submit(_set_and_return_catalog_in_another_thread, q, engine_adapter)
+
+        assert q.get() == "thread_started"
+        assert not future.done()
+
+        try:
+            assert q.get(timeout=20) == "catalog_set_in_thread"
+        except:
+            if exec := future.exception():
+                raise exec
+            raise
+
+        ctx.drop_catalog(catalog_name)
+        assert not future.done()
+
+        lock.release()  # yield the lock to the thread
+
+        # block until thread complete
+        result = future.result()
+
+        # both threads should be automatically using the default catalog now
+        assert result == default_catalog
+        assert engine_adapter.get_current_catalog() == default_catalog

tests/utils/test_connection_pool.py

@@ -210,6 +210,29 @@ def thread():
     assert cursor_mock_thread_two.begin.call_count == 1
 
 
+def test_thread_local_connection_pool_attributes(mocker: MockerFixture):
+    pool = ThreadLocalConnectionPool(connection_factory=lambda: mocker.Mock())
+
+    pool.set_attribute("foo", "bar")
+    current_threadid = get_ident()
+
+    def _in_thread(pool: ThreadLocalConnectionPool):
+        assert get_ident() != current_threadid
+        pool.set_attribute("foo", "baz")
+
+    with ThreadPoolExecutor() as executor:
+        future = executor.submit(_in_thread, pool)
+        assert not future.exception()
+
+    assert pool.get_all_attributes("foo") == ["bar", "baz"]
+    assert pool.get_attribute("foo") == "bar"
+
+    pool.close_all()
+
+    assert pool.get_all_attributes("foo") == []
+    assert pool.get_attribute("foo") is None
+
+
 def test_thread_local_shared_connection_pool(mocker: MockerFixture):
     cursor_mock_thread_one = mocker.Mock()
     cursor_mock_thread_two = mocker.Mock()