fix: Only alert on cluster drift when cluster_name is set (#5181)

Author: dehaansa

operations/alloy-mixin/alerts/clustering.libsonnet

@@ -80,11 +80,11 @@ local alert = import './utils/alert.jsonnet';
           'ClusterConfigurationDrift',
           if enableK8sCluster then |||
             count without (sha256) (
-                max by (cluster, namespace, sha256, job, cluster_name) (alloy_config_hash and on(cluster, namespace, job, cluster_name) cluster_node_info)
+                max by (cluster, namespace, sha256, job, cluster_name) (alloy_config_hash{cluster_name!=""} and on(cluster, namespace, job, cluster_name) cluster_node_info)
             ) > 1
           ||| else |||
             count without (sha256) (
-                max by (sha256, job) (alloy_config_hash and on(job) cluster_node_info)
+                max by (sha256, job) (alloy_config_hash{cluster_name!=""} and on(job) cluster_node_info)
             ) > 1
           |||
           ,

operations/alloy-mixin/rendered/alerts/alloy_clustering.yaml

@@ -51,7 +51,7 @@
       "summary": "Cluster configuration drifting."
     "expr": |
       count without (sha256) (
-          max by (cluster, namespace, sha256, job, cluster_name) (alloy_config_hash and on(cluster, namespace, job, cluster_name) cluster_node_info)
+          max by (cluster, namespace, sha256, job, cluster_name) (alloy_config_hash{cluster_name!=""} and on(cluster, namespace, job, cluster_name) cluster_node_info)
       ) > 1
     "for": "5m"
     "labels":