Fetch replicaset from etcd if not found in cache

During workload rollback, for deployments under apps/v1, we need to get
replicaset spec.
The rollback handler was getting replicaset from cache, but for HA setups
sometimes the replicaset wasn't getting returned from cache.
This commit adds fallback logic to fetch the replicaset from etcd if fetching
from cache fails

pkg/api/customization/workload/workload.go

@@ -153,6 +153,7 @@ func (a ActionWrapper) rollbackDeployment(apiContext *types.APIContext, clusterC
 		return httperror.NewAPIError(httperror.ServerError, fmt.Sprintf("Error parsing api version for deployment %v: %v", name, err))
 	}
 	if deploymentVersion == k8sappsv1.SchemeGroupVersion {
+		logrus.Debugf("Deployment apiversion is apps/v1")
 		// DeploymentRollback & RollbackTo are deprecated in apps/v1
 		// only way to rollback is update deployment podSpec with replicaSet podSpec
 		split := strings.SplitN(rollbackInput.ReplicaSetID, ":", 3)
@@ -162,13 +163,17 @@ func (a ActionWrapper) rollbackDeployment(apiContext *types.APIContext, clusterC
 		replicaNamespace, replicaName := split[1], split[2]
 		rs, err := clusterContext.Apps.ReplicaSets("").Controller().Lister().Get(replicaNamespace, replicaName)
 		if err != nil {
-			return httperror.NewAPIError(httperror.ServerError, fmt.Sprintf("ReplicaSet %s doesn't exist for deployment %s", rollbackInput.ReplicaSetID, deployment.ID))
+			logrus.Debugf("ReplicaSet not found in cache, fetching from etcd")
+			rs, err = clusterContext.Apps.ReplicaSets("").GetNamespaced(replicaNamespace, replicaName, v1.GetOptions{})
+			if err != nil {
+				return httperror.NewAPIError(httperror.ServerError, fmt.Sprintf("ReplicaSet %s not found for deployment %s", rollbackInput.ReplicaSetID, deployment.ID))
+			}
 		}
 		toUpdateDepl := depl.DeepCopy()
 		toUpdateDepl.Spec.Template.Spec = rs.Spec.Template.Spec
 		_, err = clusterContext.Apps.Deployments("").Update(toUpdateDepl)
 		if err != nil {
-			return httperror.NewAPIError(httperror.ServerError, fmt.Sprintf("Error updating workload %s by %s : %s", deployment.ID, actionName, err.Error()))
+			return httperror.NewAPIError(httperror.ServerError, fmt.Sprintf("Error updating workload under apps/v1 %s by %s : %s", deployment.ID, actionName, err.Error()))
 		}
 		return nil
 	}