Clean up cache interface, add support for services

We just added an unreleased interface method to the CloudConfig object -
but maybe that should have been more aligned with dogpile words.

SO - change the docs to reference the dogpile words and add support for
that, while keeping backwards compat support for people using max_age.
Also, do the -/_ transform on the cache config like elsewhere.

Then, while we're in there, add support for per-service cache timings.
We need this in nodepool and shade is adding support, so ability to
configure it will be important.

Change-Id: I31190a31ab0b79fc080db3611c0cd584076387d4

README.rst

@@ -168,9 +168,15 @@ understands passing through cache settings to dogpile.cache, with the following
 behaviors:
 
 * Listing no config settings means you get a null cache.
-* `cache.max_age` and nothing else gets you memory cache.
+* `cache.expiration_time` and nothing else gets you memory cache.
 * Otherwise, `cache.class` and `cache.arguments` are passed in
 
+Different cloud behaviors are also differently expensive to deal with. If you
+want to get really crazy and tweak stuff, you can specify different expiration
+times on a per-resource basis by passing values, in seconds to an expiration
+mapping keyed on the singular name of the resource. A value of `-1` indicates
+that the resource should never expire.
+
 `os-client-config` does not actually cache anything itself, but it collects
 and presents the cache information so that your various applications that
 are connecting to OpenStack can share a cache should you desire.
@@ -179,10 +185,13 @@ are connecting to OpenStack can share a cache should you desire.
 
   cache:
     class: dogpile.cache.pylibmc
-    max_age: 3600
+    expiration_time: 3600
     arguments:
       url:
         - 127.0.0.1
+    expiration:
+      server: 5
+      flavor: -1
   clouds:
     mordred:
       profile: hp

os_client_config/cloud_config.py

@@ -119,9 +119,9 @@ class CloudConfig(object):
         """Return a keystoneauth plugin from the auth credentials."""
         return self._auth
 
-    def get_cache_interval(self):
+    def get_cache_expiration_time(self):
         if self._openstack_config:
-            return self._openstack_config.get_cache_interval()
+            return self._openstack_config.get_cache_expiration_time()
 
     def get_cache_path(self):
         if self._openstack_config:
@@ -134,3 +134,20 @@ class CloudConfig(object):
     def get_cache_arguments(self):
         if self._openstack_config:
             return self._openstack_config.get_cache_arguments()
+
+    def get_cache_expiration(self):
+        if self._openstack_config:
+            return self._openstack_config.get_cache_expiration()
+
+    def get_cache_resource_expiration(self, resource):
+        """Get expiration time for a resource
+
+        :param resource: Name of the resource type
+
+        :returns: Expiration time for the resource type or None
+        """
+        if self._openstack_config:
+            expiration = self._openstack_config.get_cache_expiration()
+            if resource not in expiration:
+                return None
+            return expiration[resource]

os_client_config/config.py

@@ -182,21 +182,34 @@ class OpenStackConfig(object):
             self.cloud_config = dict(
                 clouds=dict(defaults=dict(self.defaults)))
 
-        self._cache_max_age = 0
+        self._cache_expiration_time = 0
         self._cache_path = CACHE_PATH
         self._cache_class = 'dogpile.cache.null'
         self._cache_arguments = {}
+        self._cache_expiration = {}
         if 'cache' in self.cloud_config:
-            self._cache_max_age = self.cloud_config['cache'].get(
-                'max_age', self._cache_max_age)
-            if self._cache_max_age:
+            cache_settings = self._normalize_keys(self.cloud_config['cache'])
+
+            # expiration_time used to be 'max_age' but the dogpile setting
+            # is expiration_time. Support max_age for backwards compat.
+            self._cache_expiration_time = cache_settings.get(
+                'expiration_time', cache_settings.get(
+                    'max_age', self._cache_expiration_time))
+
+            # If cache class is given, use that. If not, but if cache time
+            # is given, default to memory. Otherwise, default to nothing.
+            # to memory.
+            if self._cache_expiration_time:
                 self._cache_class = 'dogpile.cache.memory'
-            self._cache_path = os.path.expanduser(
-                self.cloud_config['cache'].get('path', self._cache_path))
             self._cache_class = self.cloud_config['cache'].get(
                 'class', self._cache_class)
-            self._cache_arguments = self.cloud_config['cache'].get(
+
+            self._cache_path = os.path.expanduser(
+                cache_settings.get('path', self._cache_path))
+            self._cache_arguments = cache_settings.get(
                 'arguments', self._cache_arguments)
+            self._cache_expiration = cache_settings.get(
+                'expiration', self._cache_expiration)
 
     def _load_config_file(self):
         return self._load_yaml_file(self._config_files)
@@ -221,11 +234,14 @@ class OpenStackConfig(object):
                 new_config[key] = value
         return new_config
 
+    def get_cache_expiration_time(self):
+        return self._cache_expiration_time
+
     def get_cache_interval(self):
-        return self._cache_max_age
+        return self._cache_expiration_time
 
     def get_cache_max_age(self):
-        return self._cache_max_age
+        return self._cache_expiration_time
 
     def get_cache_path(self):
         return self._cache_path
@@ -234,7 +250,10 @@ class OpenStackConfig(object):
         return self._cache_class
 
     def get_cache_arguments(self):
-        return self._cache_arguments
+        return self._cache_arguments.copy()
+
+    def get_cache_expiration(self):
+        return self._cache_expiration.copy()
 
     def _get_regions(self, cloud):
         if cloud not in self.cloud_config['clouds']: