introduce metric naming test (#3789)

* introduce metric naming test

Signed-off-by: zounengren <zounengren@cmss.chinamobile.com>

* Update metrics.go

Signed-off-by: zounengren <zounengren@cmss.chinamobile.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/plugin/cache/metrics.go b/plugin/cache/metrics.go
new file mode 100644
index 000000000..e82028902
--- /dev/null
+++ b/plugin/cache/metrics.go
@@ -0,0 +1,52 @@
+package cache
+
+import (
+	"github.com/coredns/coredns/plugin"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var (
+	// cacheSize is total elements in the cache by cache type.
+	cacheSize = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: plugin.Namespace,
+		Subsystem: "cache",
+		Name:      "size",
+		Help:      "The number of elements in the cache.",
+	}, []string{"server", "type"})
+	// cacheHits is counter of cache hits by cache type.
+	cacheHits = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: plugin.Namespace,
+		Subsystem: "cache",
+		Name:      "hits_total",
+		Help:      "The count of cache hits.",
+	}, []string{"server", "type"})
+	// cacheMisses is the counter of cache misses.
+	cacheMisses = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: plugin.Namespace,
+		Subsystem: "cache",
+		Name:      "misses_total",
+		Help:      "The count of cache misses.",
+	}, []string{"server"})
+	// cachePrefetches is the number of time the cache has prefetched a cached item.
+	cachePrefetches = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: plugin.Namespace,
+		Subsystem: "cache",
+		Name:      "prefetch_total",
+		Help:      "The number of time the cache has prefetched a cached item.",
+	}, []string{"server"})
+	// cacheDrops is the number responses that are not cached, because the reply is malformed.
+	cacheDrops = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: plugin.Namespace,
+		Subsystem: "cache",
+		Name:      "drops_total",
+		Help:      "The number responses that are not cached, because the reply is malformed.",
+	}, []string{"server"})
+	// servedStale is the number of requests served from stale cache entries.
+	servedStale = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: plugin.Namespace,
+		Subsystem: "cache",
+		Name:      "served_stale_total",
+		Help:      "The number of requests served from stale cache entries.",
+	}, []string{"server"})
+)