Allow dbt to cancel connections (#718)

* Save backend_pid on initiation
* Adjust OnConfigurationChangeOption import
* Use MagicMock to accomodate __getitem__ call on cursor results
* Test backend_pid usage
* Store backend_pid on connection directly

---------

Co-authored-by: Mike Alfare <[email protected]>
Co-authored-by: Teresa Martyny <[email protected]>

.changes/unreleased/Fixes-20240326-123703.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: dbt can cancel open queries upon interrupt
+time: 2024-03-26T12:37:03.17481-05:00
+custom:
+  Author: holly-evans
+  Issue: "705"

dbt/adapters/redshift/connections.py

@@ -233,27 +233,26 @@ def connect():
 class RedshiftConnectionManager(SQLConnectionManager):
     TYPE = "redshift"
 
-    def _get_backend_pid(self):
-        sql = "select pg_backend_pid()"
-        _, cursor = self.add_query(sql)
-
-        res = cursor.fetchone()
-        return res[0]
-
     def cancel(self, connection: Connection):
+        pid = connection.backend_pid  # type: ignore
+        sql = f"select pg_terminate_backend({pid})"
+        logger.debug(f"Cancel query on: '{connection.name}' with PID: {pid}")
+        logger.debug(sql)
+
         try:
-            pid = self._get_backend_pid()
+            self.add_query(sql)
         except redshift_connector.InterfaceError as e:
             if "is closed" in str(e):
                 logger.debug(f"Connection {connection.name} was already closed")
                 return
             raise
 
-        sql = f"select pg_terminate_backend({pid})"
-        cursor = connection.handle.cursor()
-        logger.debug(f"Cancel query on: '{connection.name}' with PID: {pid}")
-        logger.debug(sql)
-        cursor.execute(sql)
+    @classmethod
+    def _get_backend_pid(cls, connection):
+        with connection.handle.cursor() as c:
+            sql = "select pg_backend_pid()"
+            res = c.execute(sql).fetchone()
+        return res[0]
 
     @classmethod
     def get_response(cls, cursor: redshift_connector.Cursor) -> AdapterResponse:
@@ -325,14 +324,16 @@ def exponential_backoff(attempt: int):
             redshift_connector.DataError,
         ]
 
-        return cls.retry_connection(
+        open_connection = cls.retry_connection(
             connection,
             connect=connect_method_factory.get_connect_method(),
             logger=logger,
             retry_limit=credentials.retries,
             retry_timeout=exponential_backoff,
             retryable_exceptions=retryable_exceptions,
         )
+        open_connection.backend_pid = cls._get_backend_pid(open_connection)  # type: ignore
+        return open_connection
 
     def execute(
         self,

tests/unit/test_redshift_adapter.py

@@ -4,7 +4,7 @@
 from unittest import mock
 
 from dbt_common.exceptions import DbtRuntimeError
-from unittest.mock import Mock, call
+from unittest.mock import MagicMock, call
 
 import agate
 import dbt
@@ -67,7 +67,7 @@ def adapter(self):
             inject_adapter(self._adapter, RedshiftPlugin)
         return self._adapter
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_implicit_database_conn(self):
         connection = self.adapter.acquire_connection("dummy")
         connection.handle
@@ -84,7 +84,7 @@ def test_implicit_database_conn(self):
             **DEFAULT_SSL_CONFIG,
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_explicit_region_with_database_conn(self):
         self.config.method = "database"
 
@@ -103,7 +103,7 @@ def test_explicit_region_with_database_conn(self):
             **DEFAULT_SSL_CONFIG,
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_explicit_iam_conn_without_profile(self):
         self.config.credentials = self.config.credentials.replace(
             method="iam",
@@ -129,7 +129,7 @@ def test_explicit_iam_conn_without_profile(self):
             **DEFAULT_SSL_CONFIG,
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_conn_timeout_30(self):
         self.config.credentials = self.config.credentials.replace(connect_timeout=30)
         connection = self.adapter.acquire_connection("dummy")
@@ -147,7 +147,7 @@ def test_conn_timeout_30(self):
             **DEFAULT_SSL_CONFIG,
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_explicit_iam_conn_with_profile(self):
         self.config.credentials = self.config.credentials.replace(
             method="iam",
@@ -175,7 +175,7 @@ def test_explicit_iam_conn_with_profile(self):
             **DEFAULT_SSL_CONFIG,
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_explicit_iam_serverless_with_profile(self):
         self.config.credentials = self.config.credentials.replace(
             method="iam",
@@ -201,7 +201,7 @@ def test_explicit_iam_serverless_with_profile(self):
             **DEFAULT_SSL_CONFIG,
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_explicit_region(self):
         # Successful test
         self.config.credentials = self.config.credentials.replace(
@@ -229,7 +229,7 @@ def test_explicit_region(self):
             **DEFAULT_SSL_CONFIG,
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_explicit_region_failure(self):
         # Failure test with no region
         self.config.credentials = self.config.credentials.replace(
@@ -258,7 +258,7 @@ def test_explicit_region_failure(self):
                 **DEFAULT_SSL_CONFIG,
             )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_explicit_invalid_region(self):
         # Invalid region test
         self.config.credentials = self.config.credentials.replace(
@@ -287,7 +287,7 @@ def test_explicit_invalid_region(self):
                 **DEFAULT_SSL_CONFIG,
             )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_sslmode_disable(self):
         self.config.credentials.sslmode = "disable"
         connection = self.adapter.acquire_connection("dummy")
@@ -306,7 +306,7 @@ def test_sslmode_disable(self):
             sslmode=None,
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_sslmode_allow(self):
         self.config.credentials.sslmode = "allow"
         connection = self.adapter.acquire_connection("dummy")
@@ -325,7 +325,7 @@ def test_sslmode_allow(self):
             sslmode="verify-ca",
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_sslmode_verify_full(self):
         self.config.credentials.sslmode = "verify-full"
         connection = self.adapter.acquire_connection("dummy")
@@ -344,7 +344,7 @@ def test_sslmode_verify_full(self):
             sslmode="verify-full",
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_sslmode_verify_ca(self):
         self.config.credentials.sslmode = "verify-ca"
         connection = self.adapter.acquire_connection("dummy")
@@ -363,7 +363,7 @@ def test_sslmode_verify_ca(self):
             sslmode="verify-ca",
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_sslmode_prefer(self):
         self.config.credentials.sslmode = "prefer"
         connection = self.adapter.acquire_connection("dummy")
@@ -382,7 +382,7 @@ def test_sslmode_prefer(self):
             sslmode="verify-ca",
         )
 
-    @mock.patch("redshift_connector.connect", Mock())
+    @mock.patch("redshift_connector.connect", MagicMock())
     def test_serverless_iam_failure(self):
         self.config.credentials = self.config.credentials.replace(
             method="iam",
@@ -447,6 +447,25 @@ def test_invalid_iam_no_cluster_id(self):
 
         self.assertTrue("'cluster_id' must be provided" in context.exception.msg)
 
+    @mock.patch("redshift_connector.connect", MagicMock())
+    def test_connection_has_backend_pid(self):
+        backend_pid = 42
+
+        cursor = mock.MagicMock()
+        execute = cursor().__enter__().execute
+        execute().fetchone.return_value = (backend_pid,)
+        redshift_connector.connect().cursor = cursor
+
+        connection = self.adapter.acquire_connection("dummy")
+        connection.handle
+        assert connection.backend_pid == backend_pid
+
+        execute.assert_has_calls(
+            [
+                call("select pg_backend_pid()"),
+            ]
+        )
+
     def test_cancel_open_connections_empty(self):
         self.assertEqual(len(list(self.adapter.cancel_open_connections())), 0)
 
@@ -475,11 +494,32 @@ def test_cancel_open_connections_single(self):
             self.assertEqual(len(list(self.adapter.cancel_open_connections())), 1)
             add_query.assert_has_calls(
                 [
-                    call("select pg_backend_pid()"),
+                    call(f"select pg_terminate_backend({model.backend_pid})"),
                 ]
             )
 
-        master.handle.get_backend_pid.assert_not_called()
+        master.handle.backend_pid.assert_not_called()
+
+    @mock.patch("redshift_connector.connect", MagicMock())
+    def test_backend_pid_used_in_pg_terminate_backend(self):
+        with mock.patch.object(self.adapter.connections, "add_query") as add_query:
+            backend_pid = 42
+            query_result = (backend_pid,)
+
+            cursor = mock.MagicMock()
+            cursor().__enter__().execute().fetchone.return_value = query_result
+            redshift_connector.connect().cursor = cursor
+
+            connection = self.adapter.acquire_connection("dummy")
+            connection.handle
+
+            self.adapter.connections.cancel(connection)
+
+            add_query.assert_has_calls(
+                [
+                    call(f"select pg_terminate_backend({backend_pid})"),
+                ]
+            )
 
     def test_dbname_verification_is_case_insensitive(self):
         # Override adapter settings from setUp()