Support configurable metadata_workers

Adds config option worker-multiplier to allow configuring
the number of workers used for the metadata api when
using local dhcp or dvr.

Change-Id: I505963165f8a4fade0123c2825af00189285f168
Closes-Bug: 1707618

config.yaml

@@ -193,6 +193,15 @@ options:
       Sets vcpu_pin_set option in nova.conf which defines which pcpus that
       instance vcpus can or cannot use. For example '^0,^2' to reserve two
       cpus for the host.
+  worker-multiplier:
+    type: float
+    default:
+    description: |
+      The CPU core multiplier to use when configuring worker processes for
+      this services e.g. metadata-api. By default, the number of workers for
+      each daemon is set to twice the number of CPU cores a service unit has.
+      When deployed in a LXD container, this default value will be capped to 4
+      workers unless this configuration option is set.
   # Required if using FlatManager (nova-network)
   bridge-interface:
     type: string

hooks/nova_compute_utils.py

@@ -231,7 +231,8 @@ BASE_RESOURCE_MAP = {
                      context.LogLevelContext(),
                      context.InternalEndpointContext(),
                      SerialConsoleContext(),
-                     NovaComputeAvailabilityZoneContext()],
+                     NovaComputeAvailabilityZoneContext(),
+                     context.WorkerConfigContext()],
     },
     NOVA_API_AA_PROFILE_PATH: {
         'services': ['nova-api'],

templates/icehouse/nova.conf

@@ -43,6 +43,7 @@ glance_api_servers = {{ glance_api_servers }}
 neutron_metadata_proxy_shared_secret = {{ metadata_shared_secret }}
 service_neutron_metadata_proxy=True
 {% endif -%}
+metadata_workers = {{ workers }}
 
 {% if console_vnc_type -%}
 vnc_enabled = True

templates/kilo/nova.conf

@@ -145,6 +145,7 @@ metadata_proxy_shared_secret = {{ metadata_shared_secret }}
 service_metadata_proxy=True
 {% endif -%}
 {% endif -%}
+metadata_workers = {{ workers }}
 {% endif -%}
 
 {% if glance_api_servers -%}

templates/liberty/nova.conf

@@ -153,6 +153,7 @@ metadata_proxy_shared_secret = {{ metadata_shared_secret }}
 service_metadata_proxy=True
 {% endif -%}
 {% endif -%}
+metadata_workers = {{ workers }}
 {% endif -%}
 
 {% include "section-keystone-authtoken" %}

templates/mitaka/nova.conf

@@ -160,6 +160,7 @@ metadata_proxy_shared_secret = {{ metadata_shared_secret }}
 service_metadata_proxy=True
 {% endif -%}
 {% endif -%}
+metadata_workers = {{ workers }}
 {% endif -%}
 
 {% include "section-keystone-authtoken-mitaka" %}

templates/ocata/nova.conf

@@ -160,6 +160,7 @@ metadata_proxy_shared_secret = {{ metadata_shared_secret }}
 service_metadata_proxy=True
 {% endif -%}
 {% endif -%}
+metadata_workers = {{ workers }}
 {% endif -%}
 
 {% include "section-keystone-authtoken-mitaka" %}