fix(storages): pools are measured when shown, and only on a host's own pages

libvirt measures a pool's size and free space only when the pool is
refreshed and keeps those figures until the next refresh. The pool
lists read them without a refresh, so they showed a pool's space as of
whenever libvirt last refreshed it: two hosts sharing one pool's
storage told different free space for it, each its own refresh's. On a
test host, a 1 GiB file left libvirt's free space unchanged while df
showed 1 GiB less, until the pool was refreshed.

get_storages_info refreshes each active pool before reading it; a
refresh libvirt refuses (while a volume is cloned in the pool) leaves
the last figures, as the pool pages already do. A refresh scans the
pool's volumes, so pools are read only where one host's are shown: a
host's overview (views.host_pools, its Storage card) and its Storages
page and API. The Computes list and the new-VM dialog's host lines,
which read every host at once, no longer show pools; Compute.capacity
is the vCPUs and memory given.

vrtManager/storage.py

@@ -7,11 +7,18 @@ from vrtManager.connection import wvmConnect
 
 class wvmStorages(wvmConnect):
     def get_storages_info(self):
+        """Each pool's state, type, volume count, size and free space. An active
+        pool is refreshed first: libvirt measures its space only when it is
+        refreshed, so two hosts sharing a pool's storage told different free
+        space, each as of its own last refresh."""
         get_storages = self.get_storages()
         storages = []
         for pool in get_storages:
             stg = self.get_storage(pool)
             stg_status = stg.isActive()
+            if stg_status:
+                with contextlib.suppress(libvirt.libvirtError):  # refused while a volume is cloned in it
+                    stg.refresh(0)
             stg_type = util.get_xml_path(stg.XMLDesc(0), "/pool/@type")
             stg_vol = len(stg.listVolumes()) if stg_status else None
             _state, stg_size, _allocation, stg_free = stg.info()

vrtManager/tests/test_host_reads.py

@@ -196,3 +196,24 @@ class StoragesInfoTestCase(unittest.TestCase):
         conn.get_storage = lambda name: pool
         (info,) = conn.get_storages_info()
         self.assertEqual((info["name"], info["size"], info["free"]), ("default", 500, 120))
+        # measured now: libvirt keeps a pool's space as of its last refresh
+        self.assertEqual([c[0] for c in pool.mock_calls[:2]], ["isActive", "refresh"])
+
+    def test_a_pool_that_refuses_a_refresh_tells_its_last_space(self):
+        conn = connection(wvmStorages)
+        pool = MagicMock(**{"isActive.return_value": 1, "XMLDesc.return_value": "<pool type='dir'/>",
+                            "listVolumes.return_value": [], "info.return_value": [2, 500, 380, 120],
+                            "refresh.side_effect": libvirtError("pool is busy: a volume is cloned")})
+        conn.get_storages = lambda: ["default"]
+        conn.get_storage = lambda name: pool
+        (info,) = conn.get_storages_info()
+        self.assertEqual(info["free"], 120)
+
+    def test_an_inactive_pool_is_not_refreshed(self):
+        conn = connection(wvmStorages)
+        pool = MagicMock(**{"isActive.return_value": 0, "XMLDesc.return_value": "<pool type='dir'/>",
+                            "info.return_value": [0, 0, 0, 0]})
+        conn.get_storages = lambda: ["off"]
+        conn.get_storage = lambda name: pool
+        conn.get_storages_info()
+        pool.refresh.assert_not_called()