Ability to retain specialised pods for poolmanager functions (#2830)

- added retainPods flag to take in the number of specialized pods to retain
- add retainPods in both the create function and update function command
- modify crd keys to be typed instead of string
- keep track of function generation in case of update function operation
- add delete handler function to make sure specialized pods are deleted in case function is deleted

---------

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>
Signed-off-by: Pranoy Kundu <pranoy1998k@gmail.com>
Co-authored-by: Pranoy Kundu <pranoy1998k@gmail.com>

pkg/crd/key.go

@@ -20,21 +20,57 @@ import (
 	"fmt"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/types"
 )
 
-// CacheKey : Given metadata, create a key that uniquely identifies the contents
-// of the object. Since resourceVersion changes on every update and
-// UIDs are unique, uid+resourceVersion identifies the
-// content. (ResourceVersion may also update on status updates, so
-// this will result in some unnecessary cache misses. That should be
-// ok.)
-func CacheKey(metadata *metav1.ObjectMeta) string {
-	return fmt.Sprintf("%v_%v", metadata.UID, metadata.ResourceVersion)
+type CacheKeyUR struct {
+	UID             types.UID
+	ResourceVersion string
+}
+
+func (ck CacheKeyUR) String() string {
+	return fmt.Sprintf("%v_%v", ck.UID, ck.ResourceVersion)
+}
+
+type CacheKeyURG struct {
+	UID             types.UID
+	ResourceVersion string
+	Generation      int64
+}
+
+func (ck CacheKeyURG) String() string {
+	return fmt.Sprintf("%v_%v_%v", ck.UID, ck.ResourceVersion, ck.Generation)
 }
 
 // CacheKeyForUID create a key that uniquely identifies the
 // of the object. Since resourceVersion changes on every update and
 // UIDs are unique, we don't use resource version here
-func CacheKeyUID(metadata *metav1.ObjectMeta) string {
-	return fmt.Sprintf("%v", metadata.UID)
+func CacheKeyUIDFromMeta(metadata *metav1.ObjectMeta) types.UID {
+	return metadata.UID
+}
+
+// CacheKeyURFromMeta : Given metadata, create a key that uniquely identifies the contents
+// of the object. Since resourceVersion changes on every update and
+// UIDs are unique, uid+resourceVersion identifies the
+// content. (ResourceVersion may also update on status updates, so
+// this will result in some unnecessary cache misses. That should be
+// ok.)
+func CacheKeyURFromMeta(metadata *metav1.ObjectMeta) CacheKeyUR {
+	return CacheKeyUR{
+		UID:             metadata.UID,
+		ResourceVersion: metadata.ResourceVersion,
+	}
+}
+
+// CacheKeyURGFromMeta : Given metadata, create a key that uniquely identifies the contents
+// of the object. Since resourceVersion changes on every update and
+// UIDs are unique, uid+resourceVersion identifies the
+// content.
+// Generation is also included to identify latest generation of the object.
+func CacheKeyURGFromMeta(metadata *metav1.ObjectMeta) CacheKeyURG {
+	return CacheKeyURG{
+		UID:             metadata.UID,
+		ResourceVersion: metadata.ResourceVersion,
+		Generation:      metadata.Generation,
+	}
 }