change designed for illustrative purposes

shows how to use tags to implement a simple VLAN ids allocation scheme

diff --git a/PLC/Methods/AddSlice.py b/PLC/Methods/AddSlice.py
index bcae122..d371366 100644 (file)
--- a/PLC/Methods/AddSlice.py
+++ b/PLC/Methods/AddSlice.py
@@ -15,6 +15,17 @@ from PLC.Methods.UpdateSliceTag import UpdateSliceTag
 
 can_update = ['name', 'instantiation', 'url', 'description', 'max_nodes']
 
+# it would be much better to have this configured from the outside 
+# this is not, however, the subject of the current exercise
+# so let's keep it simple for now
+VLAN_RANGE = range(128,255) # this would be 128 .. 254 inclusively
+
+# also this would require the following code added in your Accessors_site.py
+#define_accessors(current_module, Slice, 'VlanId', 'vlan_id', 
+#                 "slice/general", "the vlan_id allocated to that slice",
+#                  get_roles=all_roles, set_roles=admin_roles)
+# see https://svn.planet-lab.org/wiki/TagsAndAccessors for more details
+
 class AddSlice(Method):
     """
     Adds a new slice. Any fields specified in slice_fields are used,
@@ -73,6 +84,40 @@ class AddSlice(Method):
             raise PLCInvalidArgument, "Invalid slice prefix %s in %s"%(login_base,name)
         site = sites[0]
 
+        #################### provisioning vlan_ids
+        # retrieve all alive slices 
+        alive_slices=Slices(self.api,{},['slice_id','name','slice_tag_ids'])
+        # build the list of their ids
+        alive_slices_ids = [ s['slice_id'] for s in alive_slices ]
+        # retrieve all the 'vlan_id' slice tags applying to these slice_ids
+        vlan_slice_tags = SliceTags (self.api,{'slice_id':alive_slices_ids,'tagname':'vlan_id'})
+        # hash them by the slice_tag_id
+        vlan_slice_tags_hashed_by_id = { slice_tag['slice_tag_id']:slice_tag for slice_tag in vlan_slice_tags }
+        # build the set of allocated vlans
+        allocated_vlan_ids = set()
+        for alive_slice in alive_slices:
+            # scan all slice tags attached to that slice
+            for slice_tag_id in alive_slice['slice_tag_ids']:
+                # discard the one that are not 'vlan_id'
+                if slice_tag_id not in vlan_slice_tags_hashed_by_id: continue
+                # retrive value and convert to int
+                slice_tag = vlan_slice_tags_hashed_by_id[slice_tag_id]
+                if slice_tag['tagname']=='vlan_id':
+                    try: 
+                        allocated_vlan_ids.add(int(slice_tag['value']))
+                    except: 
+                        import traceback
+                        traceback.print_exc()
+                        pass
+        # find a free vlan_id
+        available=set(VLAN_RANGE) - allocated_vlan_ids
+        try:
+            assigned=available.pop()
+            # piggybacking the code below that sets tags; tags value need to be strings..
+            tags['vlan_id']=str(assigned)
+        except:
+            raise Exception,"Cannot allocate slice %s, ran out of vlan_ids"%name
+
         if 'admin' not in self.caller['roles']:
             if site['site_id'] not in self.caller['site_ids']:
                 raise PLCPermissionDenied, "Slice prefix %s must match one of your sites' login_base"%login_base