Ensure consistent load order of domains and networks.

By processing JSON or YAML files via Ordered dicts.,
we ensure that domains are processed in the order they are specified
in the relevant configuration files.

Author: Yaniv Kaul

lago/utils.py

@@ -420,6 +420,10 @@ def deepcopy(original_obj):
     """
     if isinstance(original_obj, list):
         return list(deepcopy(item) for item in original_obj)
+    elif isinstance(original_obj, collections.OrderedDict):
+        return collections.OrderedDict(
+            (key, deepcopy(val)) for key, val in original_obj.items()
+        )
     elif isinstance(original_obj, dict):
         return dict((key, deepcopy(val)) for key, val in original_obj.items())
     else:
@@ -438,9 +442,21 @@ def load_virt_stream(virt_fd):
         dict: Loaded virt config
     """
     try:
-        virt_conf = json.load(virt_fd)
+        virt_conf = json.load(
+            virt_fd, object_pairs_hook=collections.OrderedDict
+        )
     except ValueError:
         virt_fd.seek(0)
+
+        # Ensure ordered dict loading from YAML. Based on
+        # http://stackoverflow.com/questions/5121931/in-python-how-can-you-load-yaml-mappings-as-ordereddicts
+        _mapping_tag = yaml.resolver.BaseResolver.DEFAULT_MAPPING_TAG
+
+        def dict_constructor(loader, node):
+            return collections.OrderedDict(loader.construct_pairs(node))
+
+        yaml.add_constructor(_mapping_tag, dict_constructor)
+
         virt_conf = yaml.load(virt_fd)
 
     return deepcopy(virt_conf)

lago/virt.py

@@ -17,6 +17,7 @@
 #
 # Refer to the README and COPYING files for full details of the license
 #
+import collections
 import functools
 import hashlib
 import json
@@ -86,11 +87,11 @@ def __init__(self, prefix, vm_specs, net_specs):
         with open(self.prefix.paths.uuid(), 'r') as uuid_fd:
             self.uuid = uuid_fd.read().strip()
 
-        self._nets = {}
+        self._nets = collections.OrderedDict()
         for name, spec in net_specs.items():
             self._nets[name] = self._create_net(spec)
 
-        self._vms = {}
+        self._vms = collections.OrderedDict()
         for name, spec in vm_specs.items():
             self._vms[name] = self._create_vm(spec)
 
@@ -244,17 +245,21 @@ def from_prefix(cls, prefix):
         virt_path = functools.partial(prefix.paths.prefixed, 'virt')
 
         with open(virt_path('env'), 'r') as f:
-            env_dom = json.load(f)
+            env_dom = json.load(f, object_pairs_hook=collections.OrderedDict)
 
-        net_specs = {}
+        net_specs = collections.OrderedDict()
         for name in env_dom['nets']:
             with open(virt_path('net-%s' % name), 'r') as f:
-                net_specs[name] = json.load(f)
+                net_specs[name] = json.load(
+                    f, object_pairs_hook=collections.OrderedDict
+                )
 
-        vm_specs = {}
+        vm_specs = collections.OrderedDict()
         for name in env_dom['vms']:
             with open(virt_path('vm-%s' % name), 'r') as f:
-                vm_specs[name] = json.load(f)
+                vm_specs[name] = json.load(
+                    f, object_pairs_hook=collections.OrderedDict
+                )
 
         return cls(prefix, vm_specs, net_specs)
 

tests/functional/fixtures/status/prefix_skel/expected.yaml

@@ -13,7 +13,8 @@ Prefix:
         eth1: {ip: !!python/unicode '192.168.202.2', network: !!python/unicode 'n1'}
       VNC port: null
       distro: !!python/unicode 'cirros'
-      metadata: {}
+      metadata: !!python/object/apply:collections.OrderedDict
+      - []
       root password: !!python/unicode '123456'
       snapshots: ''
       status: down
@@ -23,7 +24,8 @@ Prefix:
         eth1: {ip: !!python/unicode '192.168.202.3', network: !!python/unicode 'n1'}
       VNC port: null
       distro: !!python/unicode 'cirros'
-      metadata: {}
+      metadata: !!python/object/apply:collections.OrderedDict
+      - []
       root password: !!python/unicode 'cubswin:)'
       snapshots: ''
       status: down