Only Delete Backup pgtask if One Already Exists

When cleaning the existing backup pgtask Custom Resource prior to
creating a new backup for a cluster, the PostgreSQL Operator will now
only attempt to delete a prior backup pgtask if one currently exists.
This ensures that certain backups can be properly submitted and
executed in the event that the pgtask from the previous cluster backup
has been removed (either manually or by the Operator).  For instance,
this ensures that the post-restore backup executed following a cluster
restore can still be executed in the event that the user has scaled
down the cluster prior to the restore, since successfully scaling down
a replica currently results in the deletion of all pgtasks for the
specific cluster.

Author: andrewlecuyer

operator/backrest/backup.go

@@ -225,22 +225,27 @@ func CreateBackup(restclient *rest.RESTClient, namespace, clusterName, podName s
 func CleanBackupResources(restclient *rest.RESTClient, clientset *kubernetes.Clientset, namespace,
 	clusterName string) error {
 
-	pgtask := crv1.Pgtask{}
 	taskName := "backrest-backup-" + clusterName
-	// error if it already exists
-	found, err := kubeapi.Getpgtask(restclient, &pgtask, taskName, namespace)
-	if !found {
-		log.Debugf("backrest backup pgtask %s was not found so we will create it", taskName)
-	} else if err != nil {
+	// lookup the pgBackRest backup pgtask for the cluster to determine if it exsits
+	found, err := kubeapi.Getpgtask(restclient, &crv1.Pgtask{}, taskName, namespace)
+	if err != nil {
 		log.Error(err)
 		return err
 	}
 
-	log.Debugf("pgtask %s was found so we will recreate it", taskName)
-	//remove the existing pgtask
-	err = kubeapi.Deletepgtask(restclient, taskName, namespace)
-	if err != nil {
-		return err
+	// if the pgBackRest backup pgtask exits, then delete it so that a new pgBackRest backup
+	// pgtask can be created in order to initiate a new backup
+	if found {
+		log.Debugf("pgtask %s was found when cleaning backup resources prior to creating a new "+
+			"backrest backup pgtask and will be deleted", taskName)
+		// delete the existing pgBackRest backup pgtask
+		err = kubeapi.Deletepgtask(restclient, taskName, namespace)
+		if err != nil {
+			return err
+		}
+	} else {
+		log.Debugf("pgtask %s was not found when cleaning backup resources prior to creating a "+
+			"new backrest backup pgtask", taskName)
 	}
 
 	//remove previous backup job