Reserve memory/disk for dom0/host OS

Only when scheduling with distributed scheduler for now.

Adds flags:

flags.DEFINE_integer('reserved_host_disk_mb', 0,
        'Amount of disk in MB to reserve for host/dom0')
flags.DEFINE_integer('reserved_host_memory_mb', 512,
        'Amount of memory in MB to reserve for host/dom0')

Change-Id: Ib9b8a4deca241db399a8541ab21697ab08e29dd6

3 files changed, 37 insertions, 9 deletions

diff --git a/nova/scheduler/zone_manager.py b/nova/scheduler/zone_manager.py
index 3ccd5015e..f6d895a55 100644
--- a/nova/scheduler/zone_manager.py
+++ b/nova/scheduler/zone_manager.py
@@ -22,9 +22,8 @@ import thread
 import traceback
 import UserDict
 
-from novaclient import v1_1 as novaclient
-
 from eventlet import greenpool
+from novaclient import v1_1 as novaclient
 
 from nova import db
 from nova import flags
@@ -33,9 +32,13 @@ from nova import utils
 
 FLAGS = flags.FLAGS
 flags.DEFINE_integer('zone_db_check_interval', 60,
-                    'Seconds between getting fresh zone info from db.')
+        'Seconds between getting fresh zone info from db.')
 flags.DEFINE_integer('zone_failures_to_offline', 3,
-             'Number of consecutive errors before marking zone offline')
+        'Number of consecutive errors before marking zone offline')
+flags.DEFINE_integer('reserved_host_disk_mb', 0,
+        'Amount of disk in MB to reserve for host/dom0')
+flags.DEFINE_integer('reserved_host_memory_mb', 512,
+        'Amount of memory in MB to reserve for host/dom0')
 
 
 class ZoneState(object):
@@ -228,17 +231,26 @@ class ZoneManager(object):
         for compute in compute_nodes:
             all_disk = compute['local_gb']
             all_ram = compute['memory_mb']
-            host = compute['service']['host']
+            service = compute['service']
+            if not service:
+                LOG.warn(_("No service for compute ID %s") % compute['id'])
+                continue
 
+            host = service['host']
             caps = self.service_states.get(host, None)
-            host_info_map[host] = HostInfo(host, caps=caps,
-                                           free_disk_gb=all_disk,
-                                           free_ram_mb=all_ram)
+            host_info = HostInfo(host, caps=caps,
+                    free_disk_gb=all_disk, free_ram_mb=all_ram)
+            # Reserve resources for host/dom0
+            host_info.consume_resources(FLAGS.reserved_host_disk_mb * 1024,
+                    FLAGS.reserved_host_memory_mb)
+            host_info_map[host] = host_info
 
         # "Consume" resources from the host the instance resides on.
         instances = self._instance_get_all(context)
         for instance in instances:
             host = instance['host']
+            if not host:
+                continue
             host_info = host_info_map.get(host, None)
             if not host_info:
                 continue
diff --git a/nova/tests/scheduler/test_host_filter.py b/nova/tests/scheduler/test_host_filter.py
index 96f26b23c..b5b5aadef 100644
--- a/nova/tests/scheduler/test_host_filter.py
+++ b/nova/tests/scheduler/test_host_filter.py
@@ -56,7 +56,8 @@ class HostFilterTestCase(test.TestCase):
     def setUp(self):
         super(HostFilterTestCase, self).setUp()
         default_host_filters = ['AllHostsFilter']
-        self.flags(default_host_filters=default_host_filters)
+        self.flags(default_host_filters=default_host_filters,
+                reserved_host_disk_mb=0, reserved_host_memory_mb=0)
         self.instance_type = dict(name='tiny',
                 memory_mb=30,
                 vcpus=10,
@@ -139,6 +140,20 @@ class HostFilterTestCase(test.TestCase):
         self.assertEquals('host3', just_hosts[1])
         self.assertEquals('host2', just_hosts[0])
 
+    def test_instance_type_filter_reserved_memory(self):
+        self.flags(reserved_host_memory_mb=2048)
+        hf = nova.scheduler.filters.InstanceTypeFilter()
+        # filter all hosts that can support 30 ram and 300 disk after
+        # reserving 2048 ram
+        cooked = hf.instance_type_to_filter(self.instance_type)
+        all_hosts = self._get_all_hosts()
+        hosts = hf.filter_hosts(all_hosts, cooked)
+        self.assertEquals(2, len(hosts))
+        just_hosts = [host for host, hostinfo in hosts]
+        just_hosts.sort()
+        self.assertEquals('host4', just_hosts[1])
+        self.assertEquals('host3', just_hosts[0])
+
     def test_instance_type_filter_extra_specs(self):
         hf = nova.scheduler.filters.InstanceTypeFilter()
         # filter all hosts that can support 30 ram and 300 disk
diff --git a/nova/tests/scheduler/test_least_cost.py b/nova/tests/scheduler/test_least_cost.py
index ba6cdb686..a45e95181 100644
--- a/nova/tests/scheduler/test_least_cost.py
+++ b/nova/tests/scheduler/test_least_cost.py
@@ -32,6 +32,7 @@ def scale(hostinfo):
 class LeastCostTestCase(test.TestCase):
     def setUp(self):
         super(LeastCostTestCase, self).setUp()
+        self.flags(reserved_host_disk_mb=0, reserved_host_memory_mb=0)
 
         self.zone_manager = fake_zone_manager.FakeZoneManager()