fix(alerts): correct DiskBufferUsage template variable and severity casing

The DiskBufferUsage alert summary uses $labels.hostname without Go
template braces, causing the literal string "$labels.hostname" to be
displayed instead of the actual node hostname. Additionally, the
severity label uses "Warning" (capital W) while all other logging
alerts use lowercase.

Fix:
- Wrap $labels.hostname in {{ }} template braces in the summary
- Change severity from "Warning" to "warning" for consistency

Ref: https://redhat.atlassian.net/browse/LOG-9461
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: 2 people

bundle/manifests/collector_monitoring.coreos.com_v1_prometheusrule.yaml

@@ -86,15 +86,15 @@ spec:
       annotations:
         description: 'Collectors potentially consuming too much node disk, {{ $value
           }}% '
-        summary: Detected consuming too much node disk on $labels.hostname host
+        summary: Detected consuming too much node disk on {{ $labels.hostname }} host
       expr: "(label_replace(sum by(hostname) (vector_buffer_byte_size{component_kind='sink',
         buffer_type='disk'}), 'instance', '$1', 'hostname', '(.*)') \n/ on(instance)
         group_left() sum by(instance) (node_filesystem_size_bytes{mountpoint='/var'}))
         * 100  > 15\n"
       for: 5m
       labels:
         service: collector
-        severity: Warning
+        severity: warning
     - alert: CollectorSourceDiscardedLogs
       annotations:
         description: |-

config/prometheus/collector_alerts.yaml

@@ -80,14 +80,14 @@ spec:
     - alert: DiskBufferUsage
       annotations:
         description: "Collectors potentially consuming too much node disk, {{ $value }}% "
-        summary: "Detected consuming too much node disk on $labels.hostname host"
+        summary: "Detected consuming too much node disk on {{ $labels.hostname }} host"
       expr: |
         (label_replace(sum by(hostname) (vector_buffer_byte_size{component_kind='sink', buffer_type='disk'}), 'instance', '$1', 'hostname', '(.*)') 
         / on(instance) group_left() sum by(instance) (node_filesystem_size_bytes{mountpoint='/var'})) * 100  > 15
       for: 5m
       labels:
         service: collector
-        severity: Warning
+        severity: warning
     - alert: CollectorSourceDiscardedLogs
       annotations:
         description: |-