perf(vrtManager): the Computes page reads each host's VMs once

A host's capacity (Computes page, new VM dialog) came from
get_host_instances, which listed the VMs by ID and by name and then
looked each up, read its XML and its info: four calls a VM, for every
host on the page. It now uses the VM lists' get_domain_rows: the states
in one call and each VM's XML once. get_host_instances had no other
caller and is gone.

Checked on QEMU against the per-VM info of every domain (running, paused,
shut off): the same vCPUs and memory. A VM gone while the host is read
is left out instead of making the host's capacity unreadable.

vrtManager/connection.py

@@ -1225,39 +1225,6 @@ class wvmConnect(object):
             for dev in self.wvm.listAllDevices(libvirt.VIR_CONNECT_LIST_NODE_DEVICES_CAP_NET)
         ]
 
-    def get_host_instances(self, raw_mem_size=False):
-        vname = {}
-
-        def get_info(doc):
-            mem = util.get_xpath(doc, "/domain/currentMemory")
-            mem = int(mem) // 1024
-            if raw_mem_size:
-                mem = int(mem) * (1024 * 1024)
-            cur_vcpu = util.get_xpath(doc, "/domain/vcpu/@current")
-            if cur_vcpu:
-                vcpu = cur_vcpu
-            else:
-                vcpu = util.get_xpath(doc, "/domain/vcpu")
-            title = util.get_xpath(doc, "/domain/title")
-            title = title if title else ""
-            description = util.get_xpath(doc, "/domain/description")
-            description = description if description else ""
-            return mem, vcpu, title, description
-
-        for name in self.get_instances():
-            dom = self.get_instance(name)
-            xml = dom.XMLDesc(0)
-            (mem, vcpu, title, description) = util.get_xml_path(xml, func=get_info)
-            vname[dom.name()] = {
-                "status": dom.info()[0],
-                "uuid": dom.UUIDString(),
-                "vcpu": vcpu,
-                "memory": mem,
-                "title": title,
-                "description": description,
-            }
-        return vname
-
     def get_user_instances(self, name):
         dom = self.get_instance(name)
         xml = dom.XMLDesc(0)

vrtManager/hostdetails.py

@@ -111,11 +111,12 @@ class wvmHostDetails(wvmConnect):
         vcpus = {"all": 0, "running": 0}
         assigned = {"all": 0, "running": 0}
         vms = {"running": 0, "paused": 0, "shutoff": 0, "other": 0}
-        for vm in self.get_host_instances(raw_mem_size=True).values():
-            for share in ("all",) if vm["status"] == VIR_DOMAIN_SHUTOFF else ("all", "running"):
-                vcpus[share] += int(vm["vcpu"])
-                assigned[share] += vm["memory"]
-            vms[VM_STATES.get(vm["status"], "other")] += 1
+        # the VM lists' read: the states in one call, each VM's XML once
+        for (state, _max_memory, memory, vcpu), _title in self.get_domain_rows().values():
+            for share in ("all",) if state == VIR_DOMAIN_SHUTOFF else ("all", "running"):
+                vcpus[share] += vcpu
+                assigned[share] += memory * 1024
+            vms[VM_STATES.get(state, "other")] += 1
         return {"cpus": self.host_info[2], "memory": self.host_info[1] * 1048576,
                 "vcpus": vcpus, "assigned": assigned, "vms": vms}
 

vrtManager/tests/test_host_reads.py

@@ -153,11 +153,12 @@ class CapacityTestCase(unittest.TestCase):
     def test_a_host_gives_its_vms_cpus_and_memory(self):
         conn = connection(wvmHostDetails)
         gib = 1024 ** 3
-        # get_host_instances gives the vCPUs as text, the memory in bytes
-        conn.get_host_instances = MagicMock(return_value={
-            "web": {"status": VIR_DOMAIN_RUNNING, "vcpu": "4", "memory": 4 * gib},
-            "db": {"status": VIR_DOMAIN_PAUSED, "vcpu": "2", "memory": 2 * gib},
-            "old": {"status": VIR_DOMAIN_SHUTOFF, "vcpu": "8", "memory": 8 * gib},
+        kib = gib // 1024
+        # get_domain_rows: info (state, max memory KiB, memory KiB, vCPUs) and title
+        conn.get_domain_rows = MagicMock(return_value={
+            "u-web": ([VIR_DOMAIN_RUNNING, 8 * kib, 4 * kib, 4], ""),
+            "u-db": ([VIR_DOMAIN_PAUSED, 2 * kib, 2 * kib, 2], ""),
+            "u-old": ([VIR_DOMAIN_SHUTOFF, 8 * kib, 8 * kib, 8], ""),
         })
         self.assertEqual(conn.get_capacity(), {
             "cpus": 4, "memory": 2 * gib,
@@ -165,7 +166,7 @@ class CapacityTestCase(unittest.TestCase):
             "assigned": {"all": 14 * gib, "running": 6 * gib},
             "vms": {"running": 1, "paused": 1, "shutoff": 1, "other": 0},
         })
-        conn.get_host_instances.assert_called_once_with(raw_mem_size=True)
+        conn.get_domain_rows.assert_called_once_with()
 
 
 class CpuTopologyTestCase(unittest.TestCase):