Consistent uuids for VMs in layouts

* Generate a uuid from layout_name (unless woverridden) in CarthageLayout

* Use that to generate a VM level uuid assuming there is a layout.

carthage/modeling/base.py

@@ -12,6 +12,7 @@
 import types
 import typing
 from pathlib import Path
+import uuid
 from .implementation import *
 from .decorators import *
 from carthage.dependency_injection import *  # type: ignore
@@ -24,6 +25,7 @@
 from .utils import *
 
 logger = logging.getLogger(__name__)
+LAYOUT_UUID = uuid.UUID('040e488f-016b-43fe-b52d-5217f43fdf1c')
 
 __all__ = []
 
@@ -563,6 +565,14 @@ def __init__(self,  **kwargs):
                 if not kvstore.persistent_seed_path:
                     kvstore.load(str(seed_path))
 
+    @memoproperty
+    def layout_uuid(self):
+        '''
+        Returns a uuid for this layout; based on layout_name or the class's qualname.
+        '''
+        name = self.layout_name or self.__class__.__qualname__
+        return uuid.uuid5(LAYOUT_UUID, name)
+
 
 __all__ += ['CarthageLayout']
 

carthage/resources/templates/vm-config.mako

@@ -1,5 +1,4 @@
 <%
-import uuid
 model = model_in or object()
 boot_order = 1
 memory_mb = getattr(model, 'memory_mb', 8192)
@@ -9,7 +8,7 @@ disk_cache = getattr(model, 'disk_cache', 'writethrough')
 %>
 <domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
   <name>${name}</name>
-  <uuid>${uuid.uuid4()}</uuid>
+  <uuid>${uuid}</uuid>
   <memory unit='KiB'>${memory_mb*1024}</memory>
 
   <vcpu placement='static' >${cpus}</vcpu>

carthage/vm.py

@@ -13,6 +13,7 @@
 import os.path
 import shutil
 import types
+import uuid
 import mako
 import mako.lookup
 import mako.template
@@ -62,6 +63,16 @@ def __init__(self, name, *, console_needed=None,
         self.vm_running = self.machine_running
         self._operation_lock = asyncio.Lock()
 
+    @memoproperty
+    def uuid(self):
+        from .modeling import CarthageLayout
+        layout = self.injector.get_instance(InjectionKey(CarthageLayout, _optional=True))
+        if layout:
+            layout_uuid = layout.layout_uuid
+            return uuid.uuid5(layout_uuid, 'vm:'+self.full_name)
+        return uuid.uuid4()
+
+
     async def gen_volume(self):
         if self.volume is not None:
             return
@@ -97,6 +108,7 @@ async def write_config(self):
                 disk_config=disk_config,
                 if_name=lambda n: carthage.network.base.if_name(
                     "vn", self.config_layout.container_prefix, n.name, self.name),
+                uuid=self.uuid,
                 volume=self.volume))
             if self.console_needed:
                 with open(self.console_json_path, "wt") as f: