From e89340d3613d538cf9a35972f2ecc8188392728e Mon Sep 17 00:00:00 2001
From: Dmitry Kropachev <dmitry.kropachev@gmail.com>
Date: Tue, 5 May 2026 17:03:59 -0400
Subject: [PATCH] control-connection: reconnect after discounted down signal

---
 cassandra/cluster.py                  | 16 ++++++++-------
 tests/unit/test_control_connection.py | 29 +++++++++++++++++++++++++--
 2 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/cassandra/cluster.py b/cassandra/cluster.py
index 5e7a68bc1c..b35b437af4 100644
--- a/cassandra/cluster.py
+++ b/cassandra/cluster.py
@@ -2020,7 +2020,7 @@ def on_down(self, host, is_host_addition, expect_host_to_be_down=False):
         Intended for internal use only.
         """
         if self.is_shutdown:
-            return
+            return False
 
         with host.lock:
             was_up = host.is_up
@@ -2035,14 +2035,15 @@ def on_down(self, host, is_host_addition, expect_host_to_be_down=False):
                     if pool_state:
                         connected |= pool_state['open_count'] > 0
                 if connected:
-                    return
+                    return False
 
             host.set_down()
             if (not was_up and not expect_host_to_be_down) or host.is_currently_reconnecting():
-                return
+                return False
         log.warning("Host %s has been marked down", host)
 
         self.on_down_potentially_blocking(host, is_host_addition)
+        return True
 
     def on_add(self, host, refresh_nodes=True):
         if self.is_shutdown:
@@ -2134,8 +2135,8 @@ def on_remove(self, host):
     def signal_connection_failure(self, host, connection_exc, is_host_addition, expect_host_to_be_down=False):
         is_down = host.signal_connection_failure(connection_exc)
         if is_down:
-            self.on_down(host, is_host_addition, expect_host_to_be_down)
-        return is_down
+            return self.on_down(host, is_host_addition, expect_host_to_be_down)
+        return False
 
     def add_host(self, endpoint, datacenter=None, rack=None, signal=True, refresh_nodes=True, host_id=None):
         """
@@ -4226,9 +4227,10 @@ def _signal_error(self):
                 # host may be None if it's already been removed, but that indicates
                 # that errors have already been reported, so we're fine
                 if host:
-                    self._cluster.signal_connection_failure(
+                    is_down = self._cluster.signal_connection_failure(
                         host, self._connection.last_error, is_host_addition=False)
-                    return
+                    if is_down:
+                        return
 
         # if the connection is not defunct or the host already left, reconnect
         # manually
diff --git a/tests/unit/test_control_connection.py b/tests/unit/test_control_connection.py
index 037d4a8888..1cc7d7a19c 100644
--- a/tests/unit/test_control_connection.py
+++ b/tests/unit/test_control_connection.py
@@ -13,15 +13,16 @@
 # limitations under the License.
 
 import unittest
+import uuid
 
 from concurrent.futures import ThreadPoolExecutor
 from unittest.mock import Mock, ANY, call
 
 from cassandra import OperationTimedOut, SchemaTargetType, SchemaChangeType
 from cassandra.protocol import ResultMessage, RESULT_KIND_ROWS
-from cassandra.cluster import ControlConnection, _Scheduler, ProfileManager, EXEC_PROFILE_DEFAULT, ExecutionProfile
+from cassandra.cluster import Cluster, ControlConnection, _Scheduler, ProfileManager, EXEC_PROFILE_DEFAULT, ExecutionProfile
 from cassandra.pool import Host
-from cassandra.connection import EndPoint, DefaultEndPoint, DefaultEndPointFactory
+from cassandra.connection import EndPoint, DefaultEndPoint, DefaultEndPointFactory, ConnectionException
 from cassandra.policies import (SimpleConvictionPolicy, RoundRobinPolicy,
                                 ConstantReconnectionPolicy, IdentityTranslator)
 
@@ -301,6 +302,30 @@ def test_wait_for_schema_agreement_none_timeout(self):
         cc._time = self.time
         assert cc.wait_for_schema_agreement()
 
+    def test_signal_error_reconnects_when_host_down_signal_is_discounted(self):
+        cluster = Cluster(load_balancing_policy=RoundRobinPolicy(), protocol_version=4)
+        self.addCleanup(cluster.shutdown)
+
+        host = Host(DefaultEndPoint("127.0.0.1"), SimpleConvictionPolicy, host_id=uuid.uuid4())
+        host.set_up()
+        cluster.metadata.add_or_return_host(host)
+
+        session = Mock()
+        session.get_pool_state.return_value = {host: {"open_count": 1}}
+        cluster.sessions.add(session)
+
+        connection_error = ConnectionException("control connection failed", endpoint=host.endpoint)
+        cluster.control_connection._connection = Mock(
+            endpoint=host.endpoint,
+            is_defunct=True,
+            last_error=connection_error)
+        cluster.control_connection.reconnect = Mock()
+
+        cluster.control_connection._signal_error()
+
+        assert host.is_up is True
+        cluster.control_connection.reconnect.assert_called_once_with()
+
     def test_refresh_nodes_and_tokens(self):
         self.control_connection.refresh_node_list_and_token_map()
         meta = self.cluster.metadata