adopt the one-relation model

config.yaml

@@ -1 +1,10 @@
-options: {}
+# Copyright 2023 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+options:
+  config_file:
+    type: string
+    default: ""
+    description: >
+      Mimir configuration file (yaml). Refer to 
+      https://grafana.com/docs/mimir/latest/references/configuration-parameters/ for full details.

metadata.yaml

@@ -33,42 +33,8 @@ resources:
     description: OCI image for Grafana Agent
 
 requires:
-  # On the same mimir_worker interface, the coordinator will accept one relation to a worker per
-  # each Mimir component.
-  # The relation(s) determine the role(s) the worker will assume.
-  # Each Mimir worker can take on multiple roles; however, there can be no role replication among
-  # workers related to the same coordinator, which is why we force `limit: 1`.
-  # Note: relation names exactly match Mimir roles.
-  compactor:
-    interface: mimir_worker
-    limit: 1
-  distributor:
-    interface: mimir_worker
-    limit: 1
-  ingester:
-    interface: mimir_worker
-    limit: 1
-  querier:
-    interface: mimir_worker
-    limit: 1
-  query-frontend:
-    interface: mimir_worker
-    limit: 1
-  store-gateway:
-    interface: mimir_worker
-    limit: 1
-  alertmanager:
-    interface: mimir_worker
-    limit: 1
-  ruler:
-    interface: mimir_worker
-    limit: 1
-  overrides-exporter:
-    interface: mimir_worker
-    limit: 1
-  query-scheduler:
-    interface: mimir_worker
-    limit: 1
+  mimir-cluster:
+    interface: mimir_cluster
 
   s3:
     interface: s3

src/mimir_coordinator.py

@@ -10,7 +10,7 @@
 from typing import List, Optional
 
 import pydantic
-from interfaces.mimir_worker.v0.schema import MimirRole, RequirerSchema
+from interfaces.mimir_cluster.v0.schema import MimirRole, RequirerSchema
 from ops.model import ModelError, Relation, Unit
 
 logger = logging.getLogger(__name__)
@@ -49,8 +49,9 @@
 deployment to be considered robust according to the official recommendations/guidelines."""
 
 
-def _endpoint_to_role(endpoint: str) -> MimirRole:
-    return MimirRole(endpoint.replace("-", "_"))
+def _relation_to_role(relation: Relation) -> MimirRole:
+    # TODO: extract the role from the relation
+    return MimirRole(relation.role) # FIXME
 
 
 class MimirCoordinator:
@@ -77,7 +78,7 @@ def is_recommended(self) -> bool:
         return True
 
     def roles(self) -> typing.Counter[MimirRole]:
-        """Gather the roles from the mimir_worker relations and count them."""
+        """Gather the roles from the mimir_cluster relations and count them."""
         roles = Counter()
 
         for relation in self.relations:
@@ -86,8 +87,10 @@ def roles(self) -> typing.Counter[MimirRole]:
                 continue
 
             try:
-                role = _endpoint_to_role(relation.name)
+                role = _relation_to_role(relation) # TODO: get the role from relation data
+
             except ValueError:
+                # TODO: not an actual role: should probably warn
                 logger.info(f"Not a mimir-*role* relation: {relation.name}")
                 continue