Fix integration test (#279)

tests/integration/test_cos_integration.py

@@ -36,12 +36,19 @@ async def test_alerts(ops_test: OpsTest, lxd_model, k8s_model):
     await _disable_hardware_exporter(ops_test, lxd_model)
     await _export_mock_metrics(lxd_model)
 
-    model_name = ops_test.model_name
-
-    model_status = await k8s_model.get_status()
-    traefik_ip = model_status["applications"]["traefik"].public_address
-
-    prometheus_alerts_endpoint = f"http://{traefik_ip}/{model_name}-prometheus-0/api/v1/alerts"
+    # Run juju action to get the ip address that traefik is configured to serve on
+    returncode, stdout, stderr = await ops_test.run(
+        "juju",
+        "run",
+        "--format",
+        "json",
+        "traefik/0",
+        "show-proxied-endpoints",
+    )
+    json_data = json.loads(stdout)
+    proxied_endpoints = json.loads(json_data["traefik/0"]["results"]["proxied-endpoints"])
+    prometheus_url = proxied_endpoints["prometheus/0"]["url"]
+    prometheus_alerts_endpoint = f"{prometheus_url}/api/v1/alerts"
 
     cmd = ["curl", prometheus_alerts_endpoint]