MM-56876: Redis: first introduction (#27752)

```release-note
NONE
```

---------

Co-authored-by: Jesús Espino <jespinog@gmail.com>
Co-authored-by: Mattermost Build <build@mattermost.com>

server/enterprise/metrics/metrics.go

@@ -156,6 +156,7 @@ type MetricsInterfaceImpl struct {
 	SearchFileSearchesDuration prometheus.Histogram
 	StoreTimesHistograms       *prometheus.HistogramVec
 	APITimesHistograms         *prometheus.HistogramVec
+	RedisTimesHistograms       *prometheus.HistogramVec
 	SearchPostIndexCounter     prometheus.Counter
 	SearchFileIndexCounter     prometheus.Counter
 	SearchUserIndexCounter     prometheus.Counter
@@ -764,6 +765,18 @@ func New(ps *platform.PlatformService, driver, dataSource string) *MetricsInterf
 	)
 	m.Registry.MustRegister(m.APITimesHistograms)
 
+	m.RedisTimesHistograms = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace:   MetricsNamespace,
+			Subsystem:   MetricsSubsystemDB,
+			Name:        "cache_time",
+			Help:        "Time to execute the cache handler",
+			ConstLabels: additionalLabels,
+		},
+		[]string{"cache_name", "operation"},
+	)
+	m.Registry.MustRegister(m.RedisTimesHistograms)
+
 	m.SearchPostIndexCounter = prometheus.NewCounter(prometheus.CounterOpts{
 		Namespace:   MetricsNamespace,
 		Subsystem:   MetricsSubsystemSearch,
@@ -1499,6 +1512,13 @@ func (mi *MetricsInterfaceImpl) ObserveAPIEndpointDuration(handler, method, stat
 	mi.APITimesHistograms.With(prometheus.Labels{"handler": handler, "method": method, "status_code": statusCode, "origin_client": originClient, "page_load_context": pageLoadContext}).Observe(elapsed)
 }
 
+func (mi *MetricsInterfaceImpl) ObserveRedisEndpointDuration(cacheName, operation string, elapsed float64) {
+	mi.RedisTimesHistograms.With(prometheus.Labels{
+		"cache_name": cacheName,
+		"operation":  operation,
+	}).Observe(elapsed)
+}
+
 func (mi *MetricsInterfaceImpl) IncrementClusterEventType(eventType model.ClusterEvent) {
 	if event, ok := mi.ClusterEventMap[eventType]; ok {
 		event.Inc()