Collect instance capabilities from compute nodes

This change collects a list of supported instances from compute nodes.
Each supported instance is a tuple, containing the triple
(architecture, hypervisor_type, vm_mode).  This list of tuples describes
all of the instances supported by the compute node, which can then be
used by the ComputeFilter to ensure proper placement of an instance in
a heterogeneous compute node cloud.

Change-Id: I059ff55c165b372c83e63390b40a2c165df1f717

2 files changed, 28 insertions, 0 deletions

diff --git a/nova/virt/libvirt/config.py b/nova/virt/libvirt/config.py
index a53ed640f..8a924df56 100644
--- a/nova/virt/libvirt/config.py
+++ b/nova/virt/libvirt/config.py
@@ -133,6 +133,7 @@ class LibvirtConfigCapsGuest(LibvirtConfigObject):
 
         self.arch = None
         self.ostype = None
+        self.domtype = list()
 
     def parse_dom(self, xmldoc):
         super(LibvirtConfigCapsGuest, self).parse_dom(xmldoc)
@@ -142,6 +143,9 @@ class LibvirtConfigCapsGuest(LibvirtConfigObject):
                 self.ostype = c.text
             elif c.tag == "arch":
                 self.arch = c.get("name")
+                for sc in c.getchildren():
+                    if sc.tag == "domain":
+                        self.domtype.append(sc.get("type"))
 
     def format_dom(self):
         caps = super(LibvirtConfigCapsGuest, self).format_dom()
@@ -150,6 +154,10 @@ class LibvirtConfigCapsGuest(LibvirtConfigObject):
             caps.append(self._text_node("os_type", self.ostype))
         if self.arch:
             arch = etree.Element("arch", name=self.arch)
+            for dt in self.domtype:
+                dte = etree.Element("domain")
+                dte.set("type", dt)
+                arch.append(dte)
             caps.append(arch)
 
         return caps
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index bf3cec403..6abce222d 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -2055,6 +2055,24 @@ class LibvirtDriver(driver.ComputeDriver):
         """Returns the hostname of the hypervisor."""
         return self._conn.getHostname()
 
+    def get_instance_capabilities(self):
+        """Get hypervisor instance capabilities
+
+        Returns a list of tuples that describe instances the
+        hypervisor is capable of hosting.  Each tuple consists
+        of the triplet (arch, hypervisor_type, vm_mode).
+
+        :returns: List of tuples describing instance capabilities
+        """
+        caps = self.get_host_capabilities()
+        instance_caps = list()
+        for g in caps.guests:
+            for dt in g.domtype:
+                instance_cap = (g.arch, dt, g.ostype)
+                instance_caps.append(instance_cap)
+
+        return instance_caps
+
     def get_cpu_info(self):
         """Get cpuinfo information.
 
@@ -2991,6 +3009,8 @@ class HostState(object):
         data["hypervisor_type"] = self.connection.get_hypervisor_type()
         data["hypervisor_version"] = self.connection.get_hypervisor_version()
         data["hypervisor_hostname"] = self.connection.get_hypervisor_hostname()
+        data["supported_instances"] = \
+            self.connection.get_instance_capabilities()
 
         self._stats = data