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

3 files changed, 64 insertions, 0 deletions

diff --git a/nova/tests/test_libvirt.py b/nova/tests/test_libvirt.py
index b45780912..dca370866 100644
--- a/nova/tests/test_libvirt.py
+++ b/nova/tests/test_libvirt.py
@@ -2244,11 +2244,13 @@ class LibvirtConnTestCase(test.TestCase):
             guest = config.LibvirtConfigGuest()
             guest.ostype = vm_mode.HVM
             guest.arch = "x86_64"
+            guest.domtype = ["kvm"]
             caps.guests.append(guest)
 
             guest = config.LibvirtConfigGuest()
             guest.ostype = vm_mode.HVM
             guest.arch = "i686"
+            guest.domtype = ["kvm"]
             caps.guests.append(guest)
 
             return caps
@@ -2655,6 +2657,36 @@ class LibvirtConnTestCase(test.TestCase):
                   }
         self.assertEqual(actual, expect)
 
+    def test_get_instance_capabilities(self):
+        conn = libvirt_driver.LibvirtDriver(True)
+
+        def get_host_capabilities_stub(self):
+            caps = config.LibvirtConfigCaps()
+
+            guest = config.LibvirtConfigGuest()
+            guest.ostype = 'hvm'
+            guest.arch = 'x86_64'
+            guest.domtype = ['kvm', 'qemu']
+            caps.guests.append(guest)
+
+            guest = config.LibvirtConfigGuest()
+            guest.ostype = 'hvm'
+            guest.arch = 'i686'
+            guest.domtype = ['kvm']
+            caps.guests.append(guest)
+
+            return caps
+
+        self.stubs.Set(libvirt_driver.LibvirtDriver,
+                       'get_host_capabilities',
+                       get_host_capabilities_stub)
+
+        want = [('x86_64', 'kvm', 'hvm'),
+                ('x86_64', 'qemu', 'hvm'),
+                ('i686', 'kvm', 'hvm')]
+        got = conn.get_instance_capabilities()
+        self.assertEqual(want, got)
+
 
 class HostStateTestCase(test.TestCase):
 
@@ -2663,6 +2695,7 @@ class HostStateTestCase(test.TestCase):
                  '"fxsr", "clflush", "pse36", "pat", "cmov", "mca", "pge", '
                  '"mtrr", "sep", "apic"], '
                  '"topology": {"cores": "1", "threads": "1", "sockets": "1"}}')
+    instance_caps = [("x86_64", "kvm", "hvm"), ("i686", "kvm", "hvm")]
 
     class FakeConnection(object):
         """Fake connection object"""
@@ -2704,6 +2737,9 @@ class HostStateTestCase(test.TestCase):
         def get_disk_available_least(self):
             return 13091
 
+        def get_instance_capabilities(self):
+            return HostStateTestCase.instance_caps
+
     def test_update_status(self):
         self.mox.StubOutWithMock(libvirt_driver, 'LibvirtDriver')
         libvirt_driver.LibvirtDriver(True).AndReturn(self.FakeConnection())
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