watcher: add metrics for deleted pod cache

Signed-off-by: Kornilios Kourtis <kornilios@isovalent.com>

pkg/metrics/watchermetrics/watchermetrics.go

@@ -44,17 +44,26 @@ var (
 		Help:        "The total number of events for a given watcher type.",
 		ConstLabels: nil,
 	}, []string{"watcher"})
+
+	WatcherDeletedPodCacheHits = prometheus.NewCounter(prometheus.CounterOpts{
+		Namespace:   consts.MetricsNamespace,
+		Name:        "watcher_delete_pod_cache_hits",
+		Help:        "The total hits for pod information in the deleted pod cache.",
+		ConstLabels: nil,
+	})
 )
 
 func RegisterMetrics(group metrics.Group) {
 	group.MustRegister(WatcherErrors)
 	group.MustRegister(WatcherEvents)
+	group.MustRegister(WatcherDeletedPodCacheHits)
 }
 
 func InitMetrics() {
 	// Initialize metrics with labels
 	GetWatcherEvents(K8sWatcher).Add(0)
 	GetWatcherErrors(K8sWatcher, FailedToGetPodError).Add(0)
+	GetWatcherDeletedPodCacheHits().Add(0)
 }
 
 // Get a new handle on an WatcherEvents metric for a watcher type
@@ -66,3 +75,7 @@ func GetWatcherEvents(watcherType Watcher) prometheus.Counter {
 func GetWatcherErrors(watcherType Watcher, watcherError ErrorType) prometheus.Counter {
 	return WatcherErrors.WithLabelValues(watcherType.String(), string(watcherError))
 }
+
+func GetWatcherDeletedPodCacheHits() prometheus.Counter {
+	return WatcherDeletedPodCacheHits
+}

pkg/watcher/deleted_pod_cache.go

@@ -5,6 +5,7 @@ package watcher
 
 import (
 	"github.com/cilium/tetragon/pkg/logger"
+	"github.com/cilium/tetragon/pkg/metrics/watchermetrics"
 	lru "github.com/hashicorp/golang-lru/v2"
 	corev1 "k8s.io/api/core/v1"
 	v1 "k8s.io/api/core/v1"
@@ -81,5 +82,6 @@ func (c *deletedPodCache) findContainer(containerID string) (*corev1.Pod, *corev
 		return nil, nil, false
 	}
 
+	watchermetrics.GetWatcherDeletedPodCacheHits().Inc()
 	return v.pod, v.contStatus, true
 }