From 9947a87a1bcfa3af43d51e301f75f9c5d79c5714 Mon Sep 17 00:00:00 2001
From: Knative Prow Robot <knative-prow-robot@google.com>
Date: Tue, 13 Aug 2024 20:42:44 +0100
Subject: [PATCH] fix: prober cache returns StatusUnknown by default (#4052)

Signed-off-by: Calum Murray <cmurray@redhat.com>
Co-authored-by: Calum Murray <cmurray@redhat.com>
---
 control-plane/pkg/prober/async_prober.go |  2 +-
 control-plane/pkg/prober/cache.go        | 21 ++++++++++++++-------
 control-plane/pkg/prober/cache_test.go   | 11 +++++++++++
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/control-plane/pkg/prober/async_prober.go b/control-plane/pkg/prober/async_prober.go
index bfac392a66..a54390a15c 100644
--- a/control-plane/pkg/prober/async_prober.go
+++ b/control-plane/pkg/prober/async_prober.go
@@ -56,7 +56,7 @@ func NewAsync(ctx context.Context, client httpClient, port string, IPsLister IPs
 		client:    client,
 		enqueue:   enqueue,
 		logger:    logger,
-		cache:     NewLocalExpiringCache[string, Status, types.NamespacedName](ctx, cacheExpiryTime),
+		cache:     NewLocalExpiringCacheWithDefault[string, Status, types.NamespacedName](ctx, cacheExpiryTime, StatusUnknown),
 		IPsLister: IPsLister,
 		port:      port,
 	}
diff --git a/control-plane/pkg/prober/cache.go b/control-plane/pkg/prober/cache.go
index 437bf82166..49ceb93402 100644
--- a/control-plane/pkg/prober/cache.go
+++ b/control-plane/pkg/prober/cache.go
@@ -75,6 +75,9 @@ type localExpiringCache[K comparable, V, A interface{}] struct {
 	entries *list.List
 
 	expiration time.Duration
+
+	// defaultValue is the default value returned by Get
+	defaultValue V
 }
 
 type value[K comparable, V, A interface{}] struct {
@@ -86,11 +89,17 @@ type value[K comparable, V, A interface{}] struct {
 }
 
 func NewLocalExpiringCache[K comparable, V, A interface{}](ctx context.Context, expiration time.Duration) Cache[K, V, A] {
+	var defaultValue V
+	return NewLocalExpiringCacheWithDefault[K, V, A](ctx, expiration, defaultValue)
+}
+
+func NewLocalExpiringCacheWithDefault[K comparable, V, A interface{}](ctx context.Context, expiration time.Duration, defaultValue V) Cache[K, V, A] {
 	c := &localExpiringCache[K, V, A]{
-		mu:         sync.RWMutex{},
-		targets:    make(map[K]*list.Element, 64),
-		entries:    list.New().Init(),
-		expiration: expiration,
+		mu:           sync.RWMutex{},
+		targets:      make(map[K]*list.Element, 64),
+		entries:      list.New().Init(),
+		expiration:   expiration,
+		defaultValue: defaultValue,
 	}
 	go func() {
 		for {
@@ -106,8 +115,6 @@ func NewLocalExpiringCache[K comparable, V, A interface{}](ctx context.Context,
 }
 
 func (c *localExpiringCache[K, V, A]) Get(key K) (V, bool) {
-	var defaultValue V
-
 	c.mu.RLock()
 	defer c.mu.RUnlock()
 
@@ -117,7 +124,7 @@ func (c *localExpiringCache[K, V, A]) Get(key K) (V, bool) {
 			return value.value, true
 		}
 	}
-	return defaultValue, false
+	return c.defaultValue, false
 
 }
 
diff --git a/control-plane/pkg/prober/cache_test.go b/control-plane/pkg/prober/cache_test.go
index 1c17bce032..08a8cc7bf3 100644
--- a/control-plane/pkg/prober/cache_test.go
+++ b/control-plane/pkg/prober/cache_test.go
@@ -27,6 +27,17 @@ import (
 	"k8s.io/apimachinery/pkg/util/wait"
 )
 
+func TestInMemoryLocalCacheDefaults(t *testing.T) {
+	d := time.Second
+	ctx, cancel := context.WithTimeout(context.Background(), d*4)
+	defer cancel()
+	c := NewLocalExpiringCacheWithDefault[string, Status, int](ctx, d, StatusUnknown)
+
+	v, ok := c.Get("unknown")
+	require.False(t, ok)
+	require.Equal(t, v, StatusUnknown)
+}
+
 func TestInMemoryLocalCache(t *testing.T) {
 	d := time.Second
 	ctx, cancel := context.WithTimeout(context.Background(), d*4)