Change project-groups to include a costshare for each project

aws_project_costs/project-cost-schema.json

@@ -21,13 +21,25 @@
       }
     },
     "project-groups": {
-      "description": "Groups of projects which use common infrastructure, a mapping of group-name to list of projects in the group",
+      "description": "Groups of projects which use common infrastructure, a mapping of group-name to projects in the group, and their proportion of shared costs",
       "type": "object",
       "additionalProperties": {
         "type": "array",
         "items": {
-          "type": "string",
-          "minLength": 1
+          "type": "object",
+          "properties": {
+            "name": {
+              "description": "Name of the project",
+              "type": "string",
+              "minLength": 1
+            },
+            "costshare": {
+              "description": "Proportion of shared costs to be allocated to project, relative to other project shares",
+              "type": "integer",
+              "minimum": 0
+            }
+          },
+          "required": ["name", "costshare"]
         }
       }
     },

aws_project_costs/project_costs.py

@@ -13,10 +13,22 @@ def _get_account_cfg(config, accountname):
     raise ValueError(f"Configuration for account {accountname} not found")
 
 
-def _get_projects_in_groups(config, groupnames):
-    projects = set()
+def _get_project_costshares_in_groups(config, groupnames):
+    """
+    Get the combined set of all projects in groupnames, and their costshare
+    If a project is in multiple groups it must have the same costshare
+    """
+    projects = dict()
     for group in groupnames:
-        projects.update(config["project-groups"][group])
+        for p in config["project-groups"][group]:
+            name = p["name"]
+            costshare = p["costshare"]
+            if name in projects and costshare != projects[name]:
+                raise ValueError(
+                    f"Project {name} appears in multiple project groups"
+                    f"{groupnames} but has different costshares"
+                )
+            projects[name] = costshare
     return projects
 
 
@@ -69,15 +81,16 @@ def _shared_account(
             )
         else:
             # Either untagged, or a tag that should be considered shared
-            cost_per_project = item["COST"] / len(projects_in_group)
+            total_costshare = sum(projects_in_group.values())
+            cost_per_share = item["COST"] / total_costshare
             for project_name in projects_in_group:
                 rows.append(
                     (
                         start.date().isoformat(),
                         project_name,
                         description,
                         costs_tag,
-                        cost_per_project,
+                        cost_per_share * projects_in_group[project_name],
                     )
                 )
     return rows
@@ -108,7 +121,7 @@ def allocate_costs(*, accountname, config, start, df):
                 f"Project tag {project_tagname} not yet implemented"
             )
 
-        projects_in_group = _get_projects_in_groups(
+        projects_in_group = _get_project_costshares_in_groups(
             config, account_cfg["project-groups"]
         )
         rows = _shared_account(

aws_project_costs/schema.py

@@ -16,6 +16,7 @@ def validate(projects, raise_on_error=False):
 
     # Check accounts[].project-groups are valid
     # Check accounts[].name are unique
+    # Check at least one project in project-groups has a non-zero costshare
     acc_names = set()
     for acc in projects["accounts"]:
         name = acc["name"].lower()
@@ -29,6 +30,10 @@ def validate(projects, raise_on_error=False):
                     f"project-group {group} in account {acc['name']} does not exist!"
                 )
 
+    for group in acc.get("project-groups", []):
+        if set(p["costshare"] for p in group) == {0}:
+            errors.append(f"All projects in project-group {group} have costshare=0")
+
     if raise_on_error and errors:
         raise ValueError(errors)
     return errors

example/projects.yaml

@@ -9,16 +9,23 @@ shared-tag-values:
 
 project-groups:
   tre:
-    - "Project A"
-    - "Project B"
-    - "SPECIAL-OPS"
-    - "Internal - development"
-    - "Internal - training"
+    - name: "Project A"
+      costshare: 1
+    - name: "Project B"
+      costshare: 1
+    - name: "SPECIAL-OPS"
+      costshare: 1
+    - name: "Internal - development"
+      costshare: 1
+    - name: "Internal - training"
+      costshare: 1
   web:
-    - "SPECIAL-OPS"
+    - name: "SPECIAL-OPS"
+      costshare: 1
   # TODO: Should every project be in at least one group?
   other:
-    - "Complicated Project Name / 🐣 / 🐧"
+    - name: "Complicated Project Name / 🐣 / 🐧"
+      costshare: 1
 
 accounts:
   - name: "aws-auth"