experiment WIP: multitenancy

coordinator/lib/charms/grafana_k8s/v1/grafana_source.py

@@ -239,7 +239,7 @@ def __init__(self, *args):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 0
+LIBPATCH = 1
 
 logger = logging.getLogger(__name__)
 
@@ -420,6 +420,7 @@ def __init__(
         unit_datasources: bool = False,
         app_datasource_url: Optional[str] = None,
         unit_datasource_url: Optional[str] = None,
+        app_datasources: Optional[List[Dict]] = None,
     ) -> None:
         """Construct a Grafana charm client.
 
@@ -499,6 +500,11 @@ def __init__(
                 is used. This value is per-unit. Pass the base URL only: for
                 ``source_type == "mimir"`` the library appends the ``/prometheus`` query
                 path itself.
+            app_datasources: an optional list of additional application-level datasource
+                dicts to publish (under ``grafana_source_datasources``) alongside the
+                default datasource. Each entry supports the same keys as the consumer's
+                source dicts: ``source_name``, ``source_type``, ``url`` and, optionally,
+                ``extra_fields`` and ``secure_extra_fields``.
         """
         _validate_relation_by_interface_and_direction(
             charm, relation_name, RELATION_INTERFACE_NAME, RelationRole.provides
@@ -518,6 +524,7 @@ def __init__(
 
         self._extra_fields = extra_fields
         self._secure_extra_fields = secure_extra_fields
+        self._extra_app_datasources = app_datasources or []
 
         if not refresh_event:
             if len(self._charm.meta.containers) == 1:
@@ -571,6 +578,33 @@ def update_app_source(self, app_datasource_url: Optional[str] = ""):
                 continue
             self._set_sources(rel)
 
+    def update_app_datasources(
+        self, datasources: Optional[List[Dict]], app_datasource_url: Optional[str] = None
+    ) -> None:
+        """Publish extra application-level datasources and re-publish relation data.
+
+        The provided datasources are written to the app databag under
+        ``grafana_source_datasources``. Each entry must provide ``source_name``,
+        ``source_type``, ``url`` and, optionally, ``extra_fields`` and
+        ``secure_extra_fields`` (matching the shape of the consumer's source dicts).
+
+        Passing an empty list removes the key and reverts to publishing only the
+        default application-level datasource.
+
+        Args:
+            datasources: a list of datasource dicts to publish, or empty/None to clear.
+            app_datasource_url: an optional application-level URL to republish alongside
+                the extra datasources (e.g. to refresh after an ingress change).
+        """
+        self._extra_app_datasources = list(datasources or [])
+        if app_datasource_url is not None:
+            self._app_datasource_url = self._sanitize_source_url(app_datasource_url)
+
+        for rel in self._charm.model.relations.get(self._relation_name, []):
+            if not rel:
+                continue
+            self._set_sources(rel)
+
     def update_unit_source(self, unit_datasource_url: Optional[str] = ""):
         """Update this unit's datasource URL and re-publish relation data.
 
@@ -632,6 +666,13 @@ def _set_sources(self, rel: Relation):
         logger.debug("Setting Grafana data sources: %s", self._scrape_data)
         rel.data[self._charm.app]["grafana_source_data"] = json.dumps(self._scrape_data)
 
+        if self._extra_app_datasources:
+            rel.data[self._charm.app]["grafana_source_datasources"] = json.dumps(
+                self._extra_app_datasources
+            )
+        elif "grafana_source_datasources" in rel.data[self._charm.app]:
+            del rel.data[self._charm.app]["grafana_source_datasources"]
+
     @property
     def _scrape_data(self) -> Dict:
         """Generate source metadata.

coordinator/lib/charms/prometheus_k8s/v1/prometheus_remote_write.py

@@ -44,7 +44,7 @@
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 18
+LIBPATCH = 19
 
 PYDEPS = ["cosl"]
 
@@ -404,6 +404,7 @@ def __init__(
         peer_relation_name: str,
         forward_alert_rules: bool = True,
         extra_alert_labels: Dict = {},
+        mimir_tenant_id: Optional[str] = None,
     ):
         """API to manage a required relation with the `prometheus_remote_write` interface.
 
@@ -420,6 +421,9 @@ def __init__(
             peer_relation_name: Name of the peer relation containing units of this charm.
             forward_alert_rules: Flag to toggle forwarding of charmed alert rules.
             extra_alert_labels: Dict of extra labels to inject alert rules with.
+            mimir_tenant_id: The Mimir tenant ID to be announced to the remote-write
+                provider (e.g. Mimir) over the relation app data bag. If empty or None,
+                no tenant ID is sent.
 
         Raises:
             RelationNotFoundError: If there is no relation in the charm's metadata.yaml
@@ -450,6 +454,7 @@ def __init__(
         self._alert_rules_path = alert_rules_path
         self._forward_alert_rules = forward_alert_rules
         self._extra_alert_labels = extra_alert_labels
+        self._mimir_tenant_id = mimir_tenant_id or ""
         self._peer_relation_name = peer_relation_name
         self.topology = JujuTopology.from_charm(charm)
         self._tool = CosTool("promql")
@@ -528,6 +533,12 @@ def _push_alerts_to_relation_databag(self, relation: Relation) -> None:
             )
         relation.data[self._charm.app]["alert_rules"] = json.dumps(alert_rules_as_dict)
 
+        # Announce the Mimir tenant ID (if any) to the provider side (e.g. Mimir).
+        if self._mimir_tenant_id:
+            relation.data[self._charm.app]["mimir_tenant_id"] = self._mimir_tenant_id
+        elif "mimir_tenant_id" in relation.data[self._charm.app]:
+            del relation.data[self._charm.app]["mimir_tenant_id"]
+
     def reload_alerts(self) -> None:
         """Reload alert rules from disk and push to relation data."""
         self._push_alerts_to_all_relation_databags(None)
@@ -1019,3 +1030,23 @@ def _has_relation_error(self, error_key: str, error_label: str) -> bool:
 
         return False
 
+    @property
+    def mimir_tenant_ids(self) -> List[str]:
+        """Map relation IDs to the Mimir tenant IDs reported by consumers.
+
+        Consumers announce the tenant ID they are configured with (e.g. via a
+        ``mimir_tenant_id`` config option) over the relation app data bag. This
+        helper exposes the ids announced by each related consumer.
+
+        Returns:
+            A mapping of relation ID to tenant ID for each relation whose consumer
+            announced a non-empty tenant ID.
+        """
+        tenants: List[str] = []
+        for relation in self._charm.model.relations.get(self._relation_name, []):
+            if not relation.app:
+                continue
+            if tenant := relation.data[relation.app].get("mimir_tenant_id", ""):
+                tenants.append(tenant)
+        return tenants
+

coordinator/src/charm.py

@@ -442,6 +442,28 @@ def _update_prometheus_api(self) -> None:
             ingress_url=f"{self.external_url}/prometheus" if self.external_url else None,
         )
 
+    def _update_grafana_sources(self) -> None:
+        """Publish the anonymous Mimir datasource plus one per announced tenant."""
+        if not self.unit.is_leader():
+            return
+
+        base_url = f"{self.external_url or self._service_url}/prometheus"
+        extra_fields = self._build_grafana_source_extra_fields()
+        tenant_datasources = [
+            {
+                "source_name": f"mimir-tenant-{tenant}",
+                "source_type": "prometheus",
+                "url": base_url,
+                "extra_fields": extra_fields,
+                "secure_extra_fields": {"httpHeaderValue1": tenant},
+            }
+            for tenant in sorted(set(self.remote_write_provider.mimir_tenant_ids))
+        ]
+        self.grafana_source.update_app_datasources(
+            tenant_datasources,
+            app_datasource_url=base_url,
+        )
+
     def _update_datasource_exchange(self) -> None:
         """Update the grafana-datasource-exchange relations."""
         if not self.unit.is_leader():
@@ -481,9 +503,7 @@ def _reconcile(self):
         self._ensure_mimirtool()
         self._update_prometheus_api()
         self._update_datasource_exchange()
-        self.grafana_source.update_app_source(
-            app_datasource_url=f"{self.external_url or self._service_url}/prometheus"
-        )
+        self._update_grafana_sources()
         self.remote_write_provider.update_endpoint()
 
         # Open necessary service ports. needed for telemetry proxying.

worker/src/charm.py

@@ -114,7 +114,7 @@ def pebble_layer(self, worker: Worker) -> Layer:
                     "mimir": {
                         "override": "replace",
                         "summary": "mimir worker daemon",
-                        "command": f"/bin/mimir --config.file={CONFIG_FILE} -target {targets} -auth.multitenancy-enabled=false",
+                        "command": f"/bin/mimir --config.file={CONFIG_FILE} -target {targets}",
                         "startup": "enabled",
                         "environment": env,
                     }