Instance Caching

This is the work to complete the resource-metadata-caching blueprint.

* Implement an in-memory cache in the compute agent.
* Change compute-agent to populate an in-memory cache.
* Change compute-agent to use the changes-since parameter in the Nova API call .
* Change compute-agent to record the polling timestamp in the cache.
* Change compute-agent to cache the flavor and image metadata as well.

Implements blueprint resource-metadata-caching

Change-Id: I97594e082db6d8e34d9201a7ec5710978e557d6d
Signed-off-by: Jason Myers <jason@jasonamyers.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/ceilometer/nova_client.py b/ceilometer/nova_client.py
index ce5efcda..832499bd 100644
--- a/ceilometer/nova_client.py
+++ b/ceilometer/nova_client.py
@@ -136,9 +136,15 @@ class Client(object):
             setattr(instance, attr, ameta)
 
     @logged
-    def instance_get_all_by_host(self, hostname):
-        """Returns list of instances on particular host."""
+    def instance_get_all_by_host(self, hostname, since=None):
+        """Returns list of instances on particular host.
+
+        If since is supplied, it will return the instances changed since that
+        datetime. since should be in ISO Format '%Y-%m-%dT%H:%M:%SZ'
+        """
         search_opts = {'host': hostname, 'all_tenants': True}
+        if since:
+            search_opts['changes-since'] = since
         return self._with_flavor_and_image(self.nova_client.servers.list(
             detailed=True,
             search_opts=search_opts))