Dynamic inventory backup corruption fix

When multiple users and process are accessing the dynamic inventory
the inventory backup and json can get corrupted. This change checks
for inventory modifictions and only saves if needed. The backup
is also moved to right before the actual save.

Change-Id: Ifd348ddd9c21526f5b523963dd1fd247edd6b109
Closes-Bug: #1750233

osa_toolkit/filesystem.py

@@ -245,7 +245,6 @@ def load_inventory(preferred_path=None, default_inv=None, filename=None):
 
     if inventory is not False:
         logger.debug("Loaded existing inventory from {}".format(file_loaded))
-        _make_backup(load_path, file_loaded)
     else:
         logger.debug("No existing inventory, created fresh skeleton.")
         inventory = copy.deepcopy(default_inv)
@@ -264,6 +263,10 @@ def save_inventory(inventory_json, save_path):
         inventory_file = file_find(save_path)
     else:
         inventory_file = os.path.join(save_path, INVENTORY_FILENAME)
+
+    if os.path.isfile(inventory_file):
+        _make_backup(save_path, inventory_file)
+
     with open(inventory_file, 'wb') as f:
         f.write(inventory_json.encode('ascii'))
         logger.info("Inventory written")

osa_toolkit/generate.py

@@ -15,6 +15,7 @@
 #
 # (c) 2014, Kevin Carter <kevin.carter@rackspace.com>
 
+import copy
 import json
 import logging
 import netaddr
@@ -1109,6 +1110,9 @@ def main(config=None, check=False, debug=False, environment=None, **kwargs):
     # Load existing inventory file if found
     inventory, inv_path = filesys.load_inventory(config, INVENTORY_SKEL)
 
+    # Make a deep copy for change comparison
+    orig_inventory = copy.deepcopy(inventory)
+
     # Save the users container cidr as a group variable
     cidr_networks = user_defined_config.get('cidr_networks')
     if not cidr_networks:
@@ -1199,7 +1203,9 @@ def main(config=None, check=False, debug=False, environment=None, **kwargs):
         num_hosts = len(inventory['_meta']['hostvars'])
         logger.debug("%d hosts found.", num_hosts)
 
-    # Save new dynamic inventory
-    filesys.save_inventory(inventory_json, inv_path)
+    # Save new dynamic inventory only if modified
+    if orig_inventory != inventory:
+        logger.debug("Saving modified inventory")
+        filesys.save_inventory(inventory_json, inv_path)
 
     return inventory_json