v-m: Scrape Longhorn manager metrics

Each Longhorn manager pod exports metrics about the node on which it is
running.  Thus, we have to scrape every pod to get the metrics about the
whole ecosystem.

victoria-metrics/scrape.yml

@@ -243,6 +243,21 @@ scrape_configs:
     - __meta_kubernetes_node_name
     replacement: /api/v1/nodes/$1/proxy/metrics
 
+- job_name: longhorn
+  kubernetes_sd_configs:
+  - role: pod
+    namespaces:
+      names:
+      - longhorn-system
+    selectors:
+    - role: pod
+      label: app=longhorn-manager
+  relabel_configs:
+  - action: drop
+    source_labels:
+    - __meta_kubernetes_pod_container_init
+    regex: '^true$'
+
 - job_name: zincati
   metrics_path: /bridge?selector=zincati
   static_configs: