Fix XenServer's ability to boot xen type images

Fixes bug 1055431.

As the scheduler wants to boot a vm_mode=xen type of image, the host's
"supported_instances" capability is used for finding a good candidate.
In the Xapi case, this field was not populated.

This fix modifies the xapi xenhost plugin, so the Xen host capabilities
are returned back to the compute node, as "host_capabilities".
On the compute side, the mentioned information is used, to extract the
"supported_instances" information.

Change-Id: I2da11ab81f74b5b52e2c30832a694470978e21b0

nova/tests/test_xenapi.py

@@ -44,6 +44,7 @@
 from nova.virt.xenapi import agent
 from nova.virt.xenapi import driver as xenapi_conn
 from nova.virt.xenapi import fake as xenapi_fake
+from nova.virt.xenapi import host
 from nova.virt.xenapi import pool
 from nova.virt.xenapi import pool_states
 from nova.virt.xenapi import vm_utils
@@ -1275,6 +1276,43 @@ def test_get_host_uptime(self):
         result = self.conn.get_host_uptime('host')
         self.assertEqual(result, 'fake uptime')
 
+    def test_supported_instances_is_included_in_host_state(self):
+        stats = self.conn.get_host_stats()
+        self.assertTrue('supported_instances' in stats)
+
+    def test_supported_instances_is_calculated_by_to_supported_instances(self):
+
+        def to_supported_instances(somedata):
+            self.assertEquals(None, somedata)
+            return "SOMERETURNVALUE"
+        self.stubs.Set(host, 'to_supported_instances', to_supported_instances)
+
+        stats = self.conn.get_host_stats()
+        self.assertEquals("SOMERETURNVALUE", stats['supported_instances'])
+
+
+class ToSupportedInstancesTestCase(test.TestCase):
+    def test_default_return_value(self):
+        self.assertEquals([],
+            host.to_supported_instances(None))
+
+    def test_return_value(self):
+        self.assertEquals([('x86_64', 'xapi', 'xen')],
+             host.to_supported_instances([u'xen-3.0-x86_64']))
+
+    def test_invalid_values_do_not_break(self):
+        self.assertEquals([('x86_64', 'xapi', 'xen')],
+             host.to_supported_instances([u'xen-3.0-x86_64', 'spam']))
+
+    def test_multiple_values(self):
+        self.assertEquals(
+            [
+                ('x86_64', 'xapi', 'xen'),
+                ('x86_32', 'xapi', 'hvm')
+            ],
+            host.to_supported_instances([u'xen-3.0-x86_64', 'hvm-3.0-x86_32'])
+        )
+
 
 class XenAPIAutoDiskConfigTestCase(stubs.XenAPITestBase):
     def setUp(self):

nova/virt/xenapi/host.py

@@ -162,6 +162,9 @@ def update_status(self):
             data["disk_total"] = total
             data["disk_used"] = used
             data["disk_available"] = total - used
+            data["supported_instances"] = to_supported_instances(
+                data.get("host_capabilities")
+            )
             host_memory = data.get('host_memory', None)
             if host_memory:
                 data["host_memory_total"] = host_memory.get('total', 0)
@@ -173,6 +176,22 @@ def update_status(self):
             self._stats = data
 
 
+def to_supported_instances(host_capabilities):
+    if not host_capabilities:
+        return []
+
+    result = []
+    for capability in host_capabilities:
+        try:
+            ostype, _version, arch = capability.split("-")
+            result.append((arch, 'xapi', ostype))
+        except ValueError:
+            LOG.warning(
+                _("Failed to extract instance support from %s"), capability)
+
+    return result
+
+
 def call_xenhost(session, method, arg_dict):
     """There will be several methods that will need this general
     handling for interacting with the xenhost plugin, so this abstracts

plugins/xenserver/xenapi/etc/xapi.d/plugins/xenhost

@@ -398,7 +398,9 @@ def cleanup(dct):
         for oc_fld in oc.split("; "):
             ock, ocv = strip_kv(oc_fld)
             ocd[ock] = ocv
-#    out["host_capabilities"] = dct.get("capabilities", "").split("; ")
+
+    capabilities = dct.get("capabilities", "")
+    out["host_capabilities"] = capabilities.replace(";", "").split()
 #    out["host_allowed-operations"] = dct.get(
 #            "allowed-operations", "").split("; ")
 #    lsrv = dct.get("license-server", "")