ZFS Collector: Add vdev_cache_stats functionality

Signed-Off-By: Joe Handzik <joseph.t.handzik@hpe.com>

collector/fixtures/e2e-output.txt

@@ -2383,6 +2383,15 @@ node_zfsFetch_stride_hits 7.06799e+06
 # HELP node_zfsFetch_stride_misses kstat.zfs.misc.zfetchstats.stride_misses
 # TYPE node_zfsFetch_stride_misses untyped
 node_zfsFetch_stride_misses 0
+# HELP node_zfsVdevCache_delegations kstat.zfs.misc.vdev_cache_stats.delegations
+# TYPE node_zfsVdevCache_delegations untyped
+node_zfsVdevCache_delegations 40
+# HELP node_zfsVdevCache_hits kstat.zfs.misc.vdev_cache_stats.hits
+# TYPE node_zfsVdevCache_hits untyped
+node_zfsVdevCache_hits 0
+# HELP node_zfsVdevCache_misses kstat.zfs.misc.vdev_cache_stats.misses
+# TYPE node_zfsVdevCache_misses untyped
+node_zfsVdevCache_misses 0
 # HELP node_zfsZil_zil_commit_count kstat.zfs.misc.zil.zil_commit_count
 # TYPE node_zfsZil_zil_commit_count untyped
 node_zfsZil_zil_commit_count 10

collector/fixtures/proc/spl/kstat/zfs/vdev_cache_stats

@@ -0,0 +1,5 @@
+8 1 0x01 3 144 8012540758 352116106118781
+name                            type data
+delegations                     4    40
+hits                            4    0
+misses                          4    0

collector/zfs.go

@@ -35,6 +35,7 @@ type zfsSubsystemName string
 
 const (
 	arc            = zfsSubsystemName("zfsArc")
+	vdevCache      = zfsSubsystemName("zfsVdevCache")
 	zfetch         = zfsSubsystemName("zfsFetch")
 	zil            = zfsSubsystemName("zfsZil")
 	zpoolSubsystem = zfsSubsystemName("zfsPool")
@@ -81,6 +82,10 @@ func (c *zfsCollector) Update(ch chan<- prometheus.Metric) (err error) {
 	err = c.updateZil(ch)
 	if err != nil { return err }
 
+	// VdevCacheStats
+	err = c.updateVdevCacheStats(ch)
+	if err != nil { return err }
+
 	// Pool stats
 	return c.updatePoolStats(ch)
 }

collector/zfs_linux.go

@@ -30,6 +30,7 @@ const (
 	zfsProcpathBase      = "spl/kstat/zfs/"
 	zfsArcstatsExt       = "arcstats"
 	zfsFetchstatsExt     = "zfetchstats"
+	zfsVdevCacheStatsExt = "vdev_cache_stats"
 	zfsZilExt            = "zil"
 )
 
@@ -78,6 +79,18 @@ func (c *zfsCollector) updateZil(ch chan<- prometheus.Metric) (err error) {
 	})
 }
 
+func (c *zfsCollector) updateVdevCacheStats(ch chan<- prometheus.Metric) (err error) {
+	file, err := c.openProcFile(filepath.Join(zfsProcpathBase, zfsVdevCacheStatsExt))
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	return c.parseProcfsFile(file, zfsVdevCacheStatsExt, func(s zfsSysctl, v zfsMetricValue) {
+		ch <- c.constSysctlMetric(vdevCache, s, v)
+	})
+}
+
 func (c *zfsCollector) parseProcfsFile(reader io.Reader, fmt_ext string, handler func(zfsSysctl, zfsMetricValue)) (err error) {
 	scanner := bufio.NewScanner(reader)
 

collector/zfs_linux_test.go

@@ -125,3 +125,39 @@ func TestZilParsing(t *testing.T) {
 		t.Fatal("Zil parsing handler was not called for some expected sysctls")
 	}
 }
+
+func TestVdevCacheStatsParsing(t *testing.T) {
+	vdevCacheStatsFile, err := os.Open("fixtures/proc/spl/kstat/zfs/vdev_cache_stats")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer vdevCacheStatsFile.Close()
+
+	c := zfsCollector{}
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	handlerCalled := false
+	err = c.parseProcfsFile(vdevCacheStatsFile, "vdev_cache_stats", func(s zfsSysctl, v zfsMetricValue) {
+
+		if s != zfsSysctl("kstat.zfs.misc.vdev_cache_stats.delegations") {
+			return
+		}
+
+		handlerCalled = true
+
+		if v != zfsMetricValue(40) {
+			t.Fatalf("Incorrect value parsed from procfs data")
+		}
+
+	})
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !handlerCalled {
+		t.Fatal("VdevCacheStats parsing handler was not called for some expected sysctls")
+	}
+}