feat(stats): adding volume stats

[pawanpraka1]

$ curl localhost:10255/metrics | grep volume_stats

# TYPE kubelet_volume_stats_available_bytes gauge
kubelet_volume_stats_available_bytes{namespace="default",persistentvolumeclaim="csi-zfspv"} 3.053129728e+09
kubelet_volume_stats_available_bytes{namespace="default",persistentvolumeclaim="csi-zfspv1"} 4.294836224e+09
# HELP kubelet_volume_stats_capacity_bytes Capacity in bytes of the volume
# TYPE kubelet_volume_stats_capacity_bytes gauge
kubelet_volume_stats_capacity_bytes{namespace="default",persistentvolumeclaim="csi-zfspv"} 4.160421888e+09
kubelet_volume_stats_capacity_bytes{namespace="default",persistentvolumeclaim="csi-zfspv1"} 4.294967296e+09
# HELP kubelet_volume_stats_inodes Maximum number of inodes in the volume
# TYPE kubelet_volume_stats_inodes gauge
kubelet_volume_stats_inodes{namespace="default",persistentvolumeclaim="csi-zfspv"} 262144
kubelet_volume_stats_inodes{namespace="default",persistentvolumeclaim="csi-zfspv1"} 8.388422e+06
# HELP kubelet_volume_stats_inodes_free Number of free inodes in the volume
# TYPE kubelet_volume_stats_inodes_free gauge
kubelet_volume_stats_inodes_free{namespace="default",persistentvolumeclaim="csi-zfspv"} 262132
kubelet_volume_stats_inodes_free{namespace="default",persistentvolumeclaim="csi-zfspv1"} 8.388416e+06
# HELP kubelet_volume_stats_inodes_used Number of used inodes in the volume
# TYPE kubelet_volume_stats_inodes_used gauge
kubelet_volume_stats_inodes_used{namespace="default",persistentvolumeclaim="csi-zfspv"} 12
kubelet_volume_stats_inodes_used{namespace="default",persistentvolumeclaim="csi-zfspv1"} 6
# HELP kubelet_volume_stats_used_bytes Number of used bytes in the volume
# TYPE kubelet_volume_stats_used_bytes gauge
kubelet_volume_stats_used_bytes{namespace="default",persistentvolumeclaim="csi-zfspv"} 1.090514944e+09
kubelet_volume_stats_used_bytes{namespace="default",persistentvolumeclaim="csi-zfspv1"} 131072


$ curl localhost:10255/stats/summary
---
     {
      "time": "2019-12-18T09:52:26Z",
      "availableBytes": 4294836224,
      "capacityBytes": 4294967296,
      "usedBytes": 131072,
      "inodesFree": 8388416,
      "inodes": 8388422,
      "inodesUsed": 6,
      "name": "fio-vol",
      "pvcRef": {
       "name": "csi-zfspv1",
       "namespace": "default"
      }
---

Signed-off-by: Pawan pawan@mayadata.io

[codecov-io]

Codecov Report

Merging #27 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #27   +/-   ##
=======================================
  Coverage   83.33%   83.33%           
=======================================
  Files           1        1           
  Lines          72       72           
=======================================
  Hits           60       60           
  Misses         12       12

---

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