[DPE-5417] Add check to ensure peer databag populated before reconciling mysqld exporter pebble layers (#505)

* Add check to ensure peer databag populated before reconciling mysqld exporter pebble layers

* Do not return a value

* Add integration test to ensure bundle with grafana-agent integration does not error

* Add missing poetry lock file update

Author: shayancanonical

poetry.lock

@@ -459,6 +459,10 @@ def _reconcile_mysqld_exporter(
         self, event: RelationCreatedEvent | RelationBrokenEvent
     ) -> None:
         """Handle a COS relation created or broken event."""
+        if not self._is_peer_data_set:
+            logger.debug("Unit not yet ready to reconcile mysqld exporter. Waiting...")
+            return
+
         container = self.unit.get_container(CONTAINER_NAME)
         if not container.can_connect():
             # reconciliation is done on pebble ready

src/charm.py

@@ -0,0 +1,16 @@
+bundle: kubernetes
+name: testing
+applications:
+  mysql-k8s:
+    charm: {{ mysql_charm_path }}
+    trust: true
+    scale: 1
+    constraints: mem=2G
+    resources:
+      mysql-image: {{ mysql_image_source }}
+  grafana-agent-k8s:
+    charm: grafana-agent-k8s
+    channel: latest/stable
+    scale: 1
+relations:
+  - [mysql-k8s:metrics-endpoint, grafana-agent-k8s:metrics-endpoint]

tests/integration/bundle_templates/grafana_agent_integration.j2

@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+# Copyright 2024 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+import logging
+import pathlib
+import tempfile
+
+import jinja2
+import pytest
+import yaml
+from pytest_operator.plugin import OpsTest
+
+logger = logging.getLogger(__name__)
+
+METADATA = yaml.safe_load(pathlib.Path("./metadata.yaml").read_text())
+IMAGE_SOURCE = METADATA["resources"]["mysql-image"]["upstream-source"]
+TIMEOUT = 10 * 60
+
+
+@pytest.mark.group(1)
+@pytest.mark.abort_on_fail
+async def test_deploy_bundle_with_cos_integrations(ops_test: OpsTest) -> None:
+    """Test COS integrations formed before mysql is allocated and deployed."""
+    logger.info("Building the mysql-k8s charm")
+    charm_path = await ops_test.build_charm(".")
+
+    bundle_template = jinja2.Template(
+        pathlib.Path(
+            "./tests/integration/bundle_templates/grafana_agent_integration.j2"
+        ).read_text()
+    )
+    rendered_bundle = bundle_template.render(
+        mysql_charm_path=str(charm_path), mysql_image_source=IMAGE_SOURCE
+    )
+
+    with tempfile.NamedTemporaryFile(mode="w+", suffix=".yaml") as rendered_bundle_file:
+        rendered_bundle_file.write(rendered_bundle)
+        rendered_bundle_file.flush()
+
+        logger.info("Deploying grafana_agent_integration bundle")
+        await ops_test.model.deploy(f"local:{rendered_bundle_file.name}", trust=True)
+
+    logger.info("Waiting until mysql-k8s becomes active")
+    await ops_test.model.wait_for_idle(
+        apps=["mysql-k8s"],
+        status="active",
+        raise_on_blocked=True,
+        timeout=TIMEOUT,
+    )