Move memcached_servers opt into common.memorycache

Add a factory function to nova.common.memorycache which consolidates
the code to choose between real or fake memcache. This then means that
memcached_servers is used in just one place and we can move the config
option there.

blueprint: scope-config-opts
Change-Id: I67c191e0db58364eda4162b9e881606063509b9d

nova/api/ec2/__init__.py

@@ -31,6 +31,7 @@ from nova.api.ec2 import apirequest
 from nova.api.ec2 import ec2utils
 from nova.api.ec2 import faults
 from nova.api import validator
+from nova.common import memorycache
 from nova import context
 from nova import exception
 from nova.openstack.common import cfg
@@ -72,7 +73,6 @@ ec2_opts = [
 
 CONF = cfg.CONF
 CONF.register_opts(ec2_opts)
-CONF.import_opt('memcached_servers', 'nova.config')
 CONF.import_opt('use_forwarded_for', 'nova.api.auth')
 
 
@@ -162,12 +162,7 @@ class Lockout(wsgi.Middleware):
 
     def __init__(self, application):
         """middleware can use fake for testing."""
-        if CONF.memcached_servers:
-            import memcache
-        else:
-            from nova.common import memorycache as memcache
-        self.mc = memcache.Client(CONF.memcached_servers,
-                                  debug=0)
+        self.mc = memorycache.get_client()
         super(Lockout, self).__init__(application)
 
     @webob.dec.wsgify(RequestClass=wsgi.Request)

nova/api/metadata/handler.py

@@ -25,6 +25,7 @@ import webob.dec
 import webob.exc
 
 from nova.api.metadata import base
+from nova.common import memorycache
 from nova import exception
 from nova.openstack.common import cfg
 from nova.openstack.common import log as logging
@@ -33,7 +34,6 @@ from nova import wsgi
 CACHE_EXPIRATION = 15  # in seconds
 
 CONF = cfg.CONF
-CONF.import_opt('memcached_servers', 'nova.config')
 CONF.import_opt('use_forwarded_for', 'nova.api.auth')
 
 metadata_proxy_opts = [
@@ -52,17 +52,12 @@ CONF.register_opts(metadata_proxy_opts)
 
 LOG = logging.getLogger(__name__)
 
-if CONF.memcached_servers:
-    import memcache
-else:
-    from nova.common import memorycache as memcache
-
 
 class MetadataRequestHandler(wsgi.Application):
     """Serve metadata."""
 
     def __init__(self):
-        self._cache = memcache.Client(CONF.memcached_servers, debug=0)
+        self._cache = memorycache.get_client()
 
     def get_metadata_by_remote_address(self, address):
         if not address:

nova/common/memorycache.py

@@ -18,8 +18,28 @@
 
 """Super simple fake memcache client."""
 
+from nova.openstack.common import cfg
 from nova.openstack.common import timeutils
 
+memcache_opts = [
+    cfg.ListOpt('memcached_servers',
+                default=None,
+                help='Memcached servers or None for in process cache.'),
+]
+
+CONF = cfg.CONF
+CONF.register_opts(memcache_opts)
+
+
+def get_client():
+    client_cls = Client
+
+    if CONF.memcached_servers:
+        import memcache
+        client_cls = memcache.Client
+
+    return client_cls(CONF.memcached_servers, debug=0)
+
 
 class Client(object):
     """Replicates a tiny subset of memcached client interface."""

nova/config.py

@@ -54,9 +54,6 @@ global_opts = [
                     'However, the node name must be valid within '
                     'an AMQP key, and if using ZeroMQ, a valid '
                     'hostname, FQDN, or IP address'),
-    cfg.ListOpt('memcached_servers',
-                default=None,
-                help='Memcached servers or None for in process cache.'),
     cfg.BoolOpt('use_ipv6',
                 default=False,
                 help='use ipv6'),

nova/consoleauth/manager.py

@@ -20,6 +20,7 @@
 
 import time
 
+from nova.common import memorycache
 from nova import manager
 from nova.openstack.common import cfg
 from nova.openstack.common import jsonutils
@@ -39,7 +40,6 @@ consoleauth_opts = [
 
 CONF = cfg.CONF
 CONF.register_opts(consoleauth_opts)
-CONF.import_opt('memcached_servers', 'nova.config')
 
 
 class ConsoleAuthManager(manager.Manager):
@@ -49,13 +49,7 @@ class ConsoleAuthManager(manager.Manager):
 
     def __init__(self, scheduler_driver=None, *args, **kwargs):
         super(ConsoleAuthManager, self).__init__(*args, **kwargs)
-
-        if CONF.memcached_servers:
-            import memcache
-        else:
-            from nova.common import memorycache as memcache
-        self.mc = memcache.Client(CONF.memcached_servers,
-                                  debug=0)
+        self.mc = memorycache.get_client()
 
     def authorize_console(self, context, token, console_type, host, port,
                           internal_access_path):