By the way, can we round the ${{value}}% to the nearest hundredth in the message? 

    - alert: DiskBufferUsage
      annotations:
        message: 'Collectors potentially consuming too much node disk, {{ $value }}% '
        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  > 0.15\n"