Add profiles' self-scraping support

charmcraft.yaml

@@ -113,7 +113,7 @@ provides:
   self-profiling-endpoint:
     interface: parca_scrape
     description: |
-      The profiling endpoint at which profiles for this parca instance are served.
+      Endpoint to allow this parca instance profiles to be scraped by a remote parca instance.
   parca-store-endpoint:
     interface: parca_store
     description: |

lib/charms/parca_k8s/v0/parca_scrape.py

@@ -171,10 +171,11 @@ def _on_scrape_targets_changed(self, event):
 import json
 import logging
 import socket
+from cosl import JujuTopology
 from typing import List, Optional, Union
+from ops.model import Relation
 
 import ops
-from charms.observability_libs.v0.juju_topology import JujuTopology
 
 # The unique Charmhub library identifier, never change it
 LIBID = "dbc3d2e89cb24917b99c40e14354dd25"
@@ -184,7 +185,7 @@ def _on_scrape_targets_changed(self, event):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 3
+LIBPATCH = 4
 
 
 logger = logging.getLogger(__name__)
@@ -811,6 +812,22 @@ def _is_valid_unit_address(self, address: str) -> bool:
         except ValueError:
             return False
 
+    @property
+    def _relations(self) -> List[Relation]:
+        """The relations currently active on this endpoint."""
+        return self._charm.model.relations[self._relation_name]
+
+    def is_ready(self, relation: Optional[Relation] = None) -> bool:
+        """Check if the relation(s) on this endpoint are ready."""
+        relations = [relation] if relation else self._relations
+
+        if not relations:
+            logger.debug(f"no relation on {self._relation_name!r}.")
+            return False
+
+        # TODO: once we have a pydantic model, we can also check for the integrity of the databags.
+        return all((relation.app and relation.data) for relation in relations)
+
     @property
     def _scrape_jobs(self) -> list:
         """Fetch list of scrape jobs.