Added allocation-ratio config opts

Nova supports setting allocation ratios at the nova-compute level from
Liberty onwards. Prior to this allocation ratios were set at the
nova-scheduler level.

Newton introduced the Placement API, and Ocata introduced the ability to
have compute resources (Core/RAM/Disk) precomputed before passing
candidates to the FilterScheduler [0]. Pike removed CoreFilter,
RAMFilter and DiskFilter scheduler filters.

From Pike onwards valid methods for settings these allocation ratios are via:
- A call to the Placement API [1].
- Config values to supplied to nova-compute (xxx_allocation_ratio).

Stein introduced initial_xxx_allocation_ratio in response to the runtime
behaviour of the ResourceTracker [2].

Currently, the precedence of resource ratio values are:
xxx_allocation_ratio > Placement API call > initial_xxx_allocation_ratio

That is a (compute) resource provider's allocation ratios will default
to initial_xxx_allocation_ratio which may be overridden at run time by a
call to the Placement API. If xxx_allocation_ratio is set it will
override all configurations for that provider.

When not otherwise configured, we set initial_xxx_allocation_ratio to
the values provided by ncc to maintain backwards compatibility. Where
initial_xxx_allocation_ratio is not available we set
xxx_allocation_ratio.

[0] https://specs.openstack.org/openstack/nova-specs/specs/ocata/implemented/resource-providers-scheduler-db-filters.html
[1] https://docs.openstack.org/api-ref/placement/#update-resource-provider-inventories
[2] https://specs.openstack.org/openstack/nova-specs/specs/stein/implemented/initial-allocation-ratios.html

Change-Id: Ifa314e9e23e0ae5d16113cd91a7507e61f9de704
Closes-Bug: #1677223

config.yaml

@@ -763,3 +763,72 @@ options:
     description: |
       Value of bluestore compression max blob size for solid state media on
       pools requested by this charm.
+  initial-cpu-allocation-ratio:
+    type: float
+    default:
+    description: |
+      The initial value of per physical core -> virtual core ratio to use in
+      the Nova scheduler; this may be overriden at runtime by the placement API.
+      .
+      Increasing this value will increase instance density on compute nodes
+      at the expense of instance performance.
+      .
+      This option doesn't have any effect on clouds running
+      a release < Stein.
+  initial-ram-allocation-ratio:
+    type: float
+    default:
+    description: |
+      The initial value of physical ram -> virtual ram ratio to use in
+      the Nova scheduler; this may be overriden at runtime by the placement API.
+      .
+      Increasing this value will increase instance density on compute nodes
+      at the potential expense of instance performance.
+      .
+      NOTE: When in a hyper-converged architecture, make sure to make enough
+      room for infrastructure services running on your compute hosts by
+      adjusting this value.
+      .
+      This option doesn't have any effect on clouds running
+      a release < Stein.
+  initial-disk-allocation-ratio:
+    type: float
+    default:
+    description: |
+      The initial value of this disk allocation ratio. Increase the amount of
+      disk space that nova can overcommit to guests.
+      This may be overriden at runtime by the placement API.
+      .
+      Increasing this value will increase instance density on compute nodes
+      with an increased risk of hypervisor storage becoming full.
+      .
+      This option doesn't have any effect on clouds running
+      a release < Stein.
+  cpu-allocation-ratio:
+    type: float
+    default:
+    description: |
+      The per physical core -> virtual core ratio to use in the Nova scheduler.
+      .
+      Increasing this value will increase instance density on compute nodes
+      at the expense of instance performance.
+  ram-allocation-ratio:
+    type: float
+    default:
+    description: |
+      The physical ram -> virtual ram ratio to use in the Nova scheduler.
+      .
+      Increasing this value will increase instance density on compute nodes
+      at the potential expense of instance performance.
+      .
+      NOTE: When in a hyper-converged architecture, make sure to make enough
+      room for infrastructure services running on your compute hosts by
+      adjusting this value.
+  disk-allocation-ratio:
+    type: float
+    default:
+    description: |
+      Increase the amount of disk space that nova can overcommit to guests.
+      .
+      Increasing this value will increase instance density on compute nodes
+      with an increased risk of hypervisor storage becoming full.

hooks/nova_compute_context.py

@@ -905,3 +905,43 @@ class NeutronPluginSubordinateConfigContext(context.SubordinateConfigContext):
         :rtype: bool
         """
         return 'sections' in ctxt.keys()
+
+
+class NovaComputePlacementContext(context.OSContextGenerator):
+
+    def __call__(self):
+        ctxt = {}
+        cmp_os_release = CompareOpenStackReleases(os_release('nova-common'))
+
+        ctxt['initial_cpu_allocation_ratio'] =\
+            config('initial-cpu-allocation-ratio')
+        ctxt['initial_ram_allocation_ratio'] =\
+            config('initial-ram-allocation-ratio')
+        ctxt['initial_disk_allocation_ratio'] =\
+            config('initial-disk-allocation-ratio')
+
+        ctxt['cpu_allocation_ratio'] = config('cpu-allocation-ratio')
+        ctxt['ram_allocation_ratio'] = config('ram-allocation-ratio')
+        ctxt['disk_allocation_ratio'] = config('disk-allocation-ratio')
+
+        if cmp_os_release >= 'stein':
+            for ratio_config in ['initial_cpu_allocation_ratio',
+                                 'initial_ram_allocation_ratio',
+                                 'initial_disk_allocation_ratio']:
+                if ctxt[ratio_config] is None:
+                    for rid in relation_ids('cloud-compute'):
+                        for unit in related_units(rid):
+                            rel = {'rid': rid, 'unit': unit}
+                            ctxt[ratio_config] = relation_get(ratio_config,
+                                                              **rel)
+        else:
+            for ratio_config in ['cpu_allocation_ratio',
+                                 'ram_allocation_ratio',
+                                 'disk_allocation_ratio']:
+                if ctxt[ratio_config] is None:
+                    for rid in relation_ids('cloud-compute'):
+                        for unit in related_units(rid):
+                            rel = {'rid': rid, 'unit': unit}
+                            ctxt[ratio_config] = relation_get(ratio_config,
+                                                              **rel)
+        return ctxt

hooks/nova_compute_utils.py

@@ -110,6 +110,7 @@ from nova_compute_context import (
     SerialConsoleContext,
     NovaComputeAvailabilityZoneContext,
     NeutronPluginSubordinateConfigContext,
+    NovaComputePlacementContext,
 )
 
 import charmhelpers.contrib.openstack.vaultlocker as vaultlocker
@@ -233,6 +234,7 @@ BASE_RESOURCE_MAP = {
                      context.VolumeAPIContext('nova-common'),
                      SerialConsoleContext(),
                      NovaComputeAvailabilityZoneContext(),
+                     NovaComputePlacementContext(),
                      context.WorkerConfigContext(),
                      vaultlocker.VaultKVContext(
                          vaultlocker.VAULTLOCKER_BACKEND),

templates/liberty/nova.conf

@@ -134,6 +134,16 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 {% if network_manager == 'neutron' and network_manager_config -%}
 [neutron]
 url = {{ network_manager_config.neutron_url }}

templates/mitaka/nova.conf

@@ -122,6 +122,16 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 [vnc]
 {% if console_vnc_type -%}
 enabled = True

templates/newton/nova.conf

@@ -127,6 +127,16 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 [vnc]
 {% if console_vnc_type -%}
 enabled = True

templates/ocata/nova.conf

@@ -130,6 +130,16 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 [vnc]
 {% if console_vnc_type -%}
 enabled = True

templates/pike/nova.conf

@@ -116,6 +116,16 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 [vnc]
 {% if console_vnc_type -%}
 enabled = True

templates/queens/nova.conf

@@ -122,6 +122,16 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 [vnc]
 {% if console_vnc_type -%}
 enabled = True

templates/rocky/nova.conf

@@ -122,6 +122,16 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 [vnc]
 {% if console_vnc_type -%}
 enabled = True

templates/stein/nova.conf

@@ -126,6 +126,25 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if initial_cpu_allocation_ratio -%}
+initial_cpu_allocation_ratio = {{ initial_cpu_allocation_ratio }}
+{% endif -%}
+{% if initial_ram_allocation_ratio -%}
+initial_ram_allocation_ratio = {{ initial_ram_allocation_ratio }}
+{% endif -%}
+{% if initial_disk_allocation_ratio -%}
+initial_disk_allocation_ratio = {{ initial_disk_allocation_ratio }}
+{% endif -%}
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 [vnc]
 {% if console_vnc_type -%}
 enabled = True

templates/train/nova.conf

@@ -154,6 +154,25 @@ resume_guests_state_on_host_boot = {{ resume_guests_state_on_host_boot }}
 
 metadata_workers = {{ workers }}
 
+{% if initial_cpu_allocation_ratio -%}
+initial_cpu_allocation_ratio = {{ initial_cpu_allocation_ratio }}
+{% endif -%}
+{% if initial_ram_allocation_ratio -%}
+initial_ram_allocation_ratio = {{ initial_ram_allocation_ratio }}
+{% endif -%}
+{% if initial_disk_allocation_ratio -%}
+initial_disk_allocation_ratio = {{ initial_disk_allocation_ratio }}
+{% endif -%}
+{% if cpu_allocation_ratio -%}
+cpu_allocation_ratio = {{ cpu_allocation_ratio }}
+{% endif -%}
+{% if ram_allocation_ratio -%}
+ram_allocation_ratio = {{ ram_allocation_ratio }}
+{% endif -%}
+{% if disk_allocation_ratio -%}
+disk_allocation_ratio = {{ disk_allocation_ratio }}
+{% endif -%}
+
 [pci]
 {% if pci_passthrough_whitelist -%}
 passthrough_whitelist = {{ pci_passthrough_whitelist }}

unit_tests/test_nova_compute_contexts.py

@@ -1079,3 +1079,27 @@ class NeutronPluginSubordinateConfigContextTest(CharmTestCase):
             config_file='/etc/nova.conf')
         self.assertFalse(ctxt.context_complete({}))
         self.assertTrue(ctxt.context_complete({'sections': {}}))
+
+
+class NovaComputePlacementContextTest(CharmTestCase):
+
+    def setUp(self):
+        super(NovaComputePlacementContextTest, self).setUp(context, TO_PATCH)
+        self.config.side_effect = self.test_config.get
+        self.os_release.return_value = 'train'
+        self.maxDiff = None
+
+    def test_allocation_ratio(self):
+        self.test_config.set('cpu-allocation-ratio', 64)
+        self.test_config.set('ram-allocation-ratio', 32.3)
+        self.test_config.set('disk-allocation-ratio', 16)
+
+        ctxt = context.NovaComputePlacementContext()
+
+        self.assertEqual(
+            {'cpu_allocation_ratio': 64,
+             'ram_allocation_ratio': 32.3,
+             'disk_allocation_ratio': 16,
+             'initial_cpu_allocation_ratio': None,
+             'initial_ram_allocation_ratio': None,
+             'initial_disk_allocation_ratio': None}, ctxt())