VM caching on export/import

Author: ydirson

conftest.py

@@ -373,6 +373,13 @@ def create_vms(request, host):
     >    ...
 
     """
+    # Do we cache VMs?
+    try:
+        from data import CACHE_IMPORTED_VM
+    except ImportError:
+        CACHE_IMPORTED_VM = False
+    assert CACHE_IMPORTED_VM in [True, False]
+
     markers = request.node.get_closest_marker("vm_definitions")
     if markers is None:
         raise Exception("No vm_definitions marker specified.")
@@ -392,7 +399,7 @@ def create_vms(request, host):
             if "template" in marker:
                 _create_vm(marker, host, vms, vdis, vbds)
             elif "image" in marker:
-                _import_vm(marker, host, vms)
+                _import_vm(marker, host, vms, use_cache=CACHE_IMPORTED_VM)
         yield vms
 
     except Exception:
@@ -440,10 +447,19 @@ def _create_vm(marker, host, vms, vdis, vbds):
             logging.info("Setting param %s", param_def)
             vm.param_set(**param_def)
 
-def _import_vm(marker, host, vms):
+def _import_vm(marker, host, vms, *, use_cache):
     vm_name = marker["name"]
     vm_image = marker["image"]
-    vm = host.import_vm(vm_image)
+    base_vm = host.import_vm(vm_image, sr_uuid=host.main_sr_uuid(), use_cache=use_cache)
+
+    if use_cache:
+        # Clone the VM before running tests, so that the original VM remains untouched
+        logging.info(">> Clone cached VM before running tests")
+        vm = base_vm.clone()
+        # Remove the description, which may contain a cache identifier
+        vm.param_set('name-description', "")
+    else:
+        vm = base_vm
     vms.append(vm)
 
 @pytest.fixture(scope="module")

lib/basevm.py

@@ -67,11 +67,18 @@ def get_sr(self):
         assert sr.attached_to_host(self.host)
         return sr
 
-    def export(self, filepath, compress='none'):
-        logging.info("Export VM %s to %s with compress=%s" % (self.uuid, filepath, compress))
-        params = {
-            'uuid': self.uuid,
-            'compress': compress,
-            'filename': filepath
-        }
-        self.host.xe('vm-export', params)
+    def export(self, filepath, compress='none', use_cache=False):
+
+        if use_cache:
+            logging.info("Export VM %s to cache for %r as a clone" % (self.uuid, filepath))
+            clone = self.clone()
+            logging.info(f"Marking VM {clone.uuid} as cached")
+            clone.param_set('name-description', self.host.vm_cache_key(filepath))
+        else:
+            logging.info("Export VM %s to %s with compress=%s" % (self.uuid, filepath, compress))
+            params = {
+                'uuid': self.uuid,
+                'compress': compress,
+                'filename': filepath
+            }
+            self.host.xe('vm-export', params)

lib/host.py

@@ -200,10 +200,14 @@ def xo_server_reconnect(self):
         # is not enough to guarantee that the host object exists yet.
         wait_for(lambda: xo_object_exists(self.uuid), "Wait for XO to know about HOST %s" % self.uuid)
 
+    @staticmethod
+    def vm_cache_key(uri):
+        return f"[Cache for {uri}]"
+
     def import_vm(self, uri, sr_uuid=None, use_cache=False):
         if use_cache:
             assert sr_uuid, "A SR UUID is necessary to use import cache"
-            cache_key = f"[Cache for {uri}]"
+            cache_key = self.vm_cache_key(uri)
             # Look for an existing cache VM
             vm_uuids = safe_split(self.xe('vm-list', {'name-description': cache_key}, minimal=True), ',')
 

tests/install/test_install.py

@@ -8,6 +8,12 @@
 from lib.host import Host
 from lib.pool import Pool
 
+try:
+    from data import CACHE_IMPORTED_VM
+except ImportError:
+    CACHE_IMPORTED_VM = False
+assert CACHE_IMPORTED_VM in [True, False]
+
 class TestInstallNested:
     @pytest.mark.vm_definitions(
         dict(name="vm 1",
@@ -111,7 +117,8 @@ def test_install_nested_821_uefi(self, iso_remaster, create_vms):
         # FIXME move to fixture
         # FIXME where to store?
         host_vm.host.ssh(["rm -f test_install_nested_821_uefi-vm1.xva"])
-        host_vm.export("test_install_nested_821_uefi-vm1.xva", "zstd")
+        host_vm.export("test_install_nested_821_uefi-vm1.xva", "zstd",
+                       use_cache=CACHE_IMPORTED_VM)
 
     @pytest.mark.vm_definitions(
         dict(name="vm 1",
@@ -213,4 +220,5 @@ def test_firstboot_nested_821_uefi(self, create_vms):
         # FIXME move to fixture
         # FIXME where to store?
         host_vm.host.ssh(["rm -f test_firstboot_nested_821_uefi-vm1.xva"])
-        host_vm.export("test_firstboot_nested_821_uefi-vm1.xva", "zstd")
+        host_vm.export("test_firstboot_nested_821_uefi-vm1.xva", "zstd",
+                       use_cache=CACHE_IMPORTED_VM)