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.

Change-Id: Ie3a7d6aab0d9902a6637637fbf75b2df3ec084b1
Closes-Bug: 1707618

config.yaml

@@ -207,6 +207,15 @@ options:
       .
       Multiple devices can be configured by providing multi values delimited by
       spaces.
+  worker-multiplier:
+    type: float
+    default:
+    description: |
+      The CPU core multiplier to use when configuring worker processes for
+      this services e.g. metadata-agent. 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.
   # Network config (by default all access is over 'private-address')
   os-data-network:
     type: string

hooks/neutron_ovs_utils.py

@@ -62,6 +62,7 @@ from charmhelpers.contrib.openstack.neutron import (
 from charmhelpers.contrib.openstack.context import (
     ExternalPortContext,
     DataPortContext,
+    WorkerConfigContext,
 )
 from charmhelpers.core.host import (
     adduser,
@@ -184,7 +185,8 @@ METADATA_RESOURCE_MAP = OrderedDict([
     (NEUTRON_METADATA_AGENT_CONF, {
         'services': ['neutron-metadata-agent'],
         'contexts': [neutron_ovs_context.SharedSecretContext(),
-                     neutron_ovs_context.APIIdentityServiceContext()],
+                     neutron_ovs_context.APIIdentityServiceContext(),
+                     WorkerConfigContext()],
     }),
 ])
 DHCP_RESOURCE_MAP = OrderedDict([

templates/icehouse/metadata_agent.ini

@@ -17,3 +17,4 @@ state_path = /var/lib/neutron
 nova_metadata_port = 8775
 metadata_proxy_shared_secret = {{ shared_secret }}
 cache_url = memory://?default_ttl=5
+metadata_workers = {{ workers }}

templates/juno/metadata_agent.ini

@@ -17,3 +17,4 @@ state_path = /var/lib/neutron
 nova_metadata_port = 8775
 metadata_proxy_shared_secret = {{ shared_secret }}
 cache_url = memory://?default_ttl=5
+metadata_workers = {{ workers }}