Merge "Drop code from Host maintenance strategy migrating instance to disabled hosts"

releasenotes/notes/donot-run-host-migration-strategy-on-disabled-hosts-24084a22d4c8f914.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    Host maintenance strategy should migrate servers based on backup node if specified
+    or rely on nova scheduler. It was enabling disabled hosts with watcher_disabled
+    reason and migrating servers to those nodes. It can impact customer workload. Compute
+    nodes were disabled for a reason.
+
+    Host maintenance strategy is fixed now to support migrating servers only on backup
+    node or rely on nova scheduler if no backup node is provided.

watcher/decision_engine/strategy/strategies/host_maintenance.py

@@ -53,7 +53,6 @@ class HostMaintenance(base.HostMaintenanceBaseStrategy):
 
     INSTANCE_MIGRATION = "migrate"
     CHANGE_NOVA_SERVICE_STATE = "change_nova_service_state"
-    REASON_FOR_DISABLE = 'watcher_disabled'
 
     def __init__(self, config, osc=None):
         super(HostMaintenance, self).__init__(config, osc)
@@ -95,10 +94,6 @@ class HostMaintenance(base.HostMaintenanceBaseStrategy):
                 cn.status == element.ServiceState.DISABLED.value and
                 cn.disabled_reason == reason}
 
-    def get_disabled_compute_nodes(self):
-        return self.get_disabled_compute_nodes_with_reason(
-            self.REASON_FOR_DISABLE)
-
     def get_instance_state_str(self, instance):
         """Get instance state in string format"""
         if isinstance(instance.state, str):
@@ -215,8 +210,7 @@ class HostMaintenance(base.HostMaintenanceBaseStrategy):
         """safe maintain one compute node
 
         Migrate all instances of the maintenance_node intensively to the
-        backup host. If the user didn't give the backup host, it will
-        select one unused node to backup the maintaining node.
+        backup host.
 
         It calculate the resource both of the backup node and maintaining
         node to evaluate the migrations from maintaining node to backup node.
@@ -233,22 +227,6 @@ class HostMaintenance(base.HostMaintenanceBaseStrategy):
                 self.host_migration(maintenance_node, backup_node)
                 return True
 
-        # If the user didn't give the backup host, select one unused
-        # node with required capacity, then migrates all instances
-        # from maintaining node to it.
-        nodes = sorted(
-            self.get_disabled_compute_nodes().values(),
-            key=lambda x: self.get_node_capacity(x)['cpu'])
-        if maintenance_node in nodes:
-            nodes.remove(maintenance_node)
-
-        for node in nodes:
-            if self.host_fits(maintenance_node, node):
-                self.enable_compute_node_if_disabled(node)
-                self.add_action_maintain_compute_node(maintenance_node)
-                self.host_migration(maintenance_node, node)
-                return True
-
         return False
 
     def try_maintain(self, maintenance_node):

watcher/tests/decision_engine/strategy/strategies/test_host_maintenance.py

@@ -167,12 +167,15 @@ class TestHostMaintenance(TestBaseStrategy):
         node_1 = model.get_node_by_uuid('Node_1')
         self.assertFalse(self.strategy.safe_maintain(node_0))
         self.assertFalse(self.strategy.safe_maintain(node_1))
+        # It will return true, if backup node is passed
+        self.assertTrue(self.strategy.safe_maintain(node_0, node_1))
 
         model = self.fake_c_cluster.\
             generate_scenario_1_with_all_nodes_disable()
         self.m_c_model.return_value = model
         node_0 = model.get_node_by_uuid('Node_0')
-        self.assertTrue(self.strategy.safe_maintain(node_0))
+        # It will return false, if there is no backup node
+        self.assertFalse(self.strategy.safe_maintain(node_0))
 
     def test_try_maintain(self):
         model = self.fake_c_cluster.generate_scenario_1()