Add new --wait-for-creation flag in kubectl wait command

kubectl wait command errors out when the waited resource does not exist.
But we need to provide a way to the users about intentionally also waiting for
the creation of resources.

This PR introduces a new flag to cover waiting for the creation of resources
with preserving the default behavior.

Author: ardaguclu

staging/src/k8s.io/kubectl/pkg/cmd/wait/wait.go

@@ -82,7 +82,10 @@ var (
 
 		# Wait for the pod "busybox1" to be deleted, with a timeout of 60s, after having issued the "delete" command
 		kubectl delete pod/busybox1
-		kubectl wait --for=delete pod/busybox1 --timeout=60s`))
+		kubectl wait --for=delete pod/busybox1 --timeout=60s
+
+		# Wait for the creation of the service "loadbalancer" in addition to wait to have ingress
+		kubectl wait --for=jsonpath='{.status.loadBalancer.ingress}' service/loadbalancer --wait-for-creation`))
 )
 
 // errNoMatchingResources is returned when there is no resources matching a query.
@@ -96,8 +99,9 @@ type WaitFlags struct {
 	PrintFlags           *genericclioptions.PrintFlags
 	ResourceBuilderFlags *genericclioptions.ResourceBuilderFlags
 
-	Timeout      time.Duration
-	ForCondition string
+	Timeout         time.Duration
+	ForCondition    string
+	WaitForCreation bool
 
 	genericiooptions.IOStreams
 }
@@ -115,7 +119,8 @@ func NewWaitFlags(restClientGetter genericclioptions.RESTClientGetter, streams g
 			WithLocal(false).
 			WithLatest(),
 
-		Timeout: 30 * time.Second,
+		Timeout:         30 * time.Second,
+		WaitForCreation: true,
 
 		IOStreams: streams,
 	}
@@ -152,6 +157,7 @@ func (flags *WaitFlags) AddFlags(cmd *cobra.Command) {
 
 	cmd.Flags().DurationVar(&flags.Timeout, "timeout", flags.Timeout, "The length of time to wait before giving up.  Zero means check once and don't wait, negative means wait for a week.")
 	cmd.Flags().StringVar(&flags.ForCondition, "for", flags.ForCondition, "The condition to wait on: [delete|condition=condition-name[=condition-value]|jsonpath='{JSONPath expression}'=[JSONPath value]]. The default condition-value is true.  Condition values are compared after Unicode simple case folding, which is a more general form of case-insensitivity.")
+	cmd.Flags().BoolVar(&flags.WaitForCreation, "wait-for-creation", flags.WaitForCreation, "The default value is true. If set to true, also wait for creation of objects if they do not already exist. This flag is ignored in --for=delete")
 }
 
 // ToOptions converts from CLI inputs to runtime inputs
@@ -180,10 +186,11 @@ func (flags *WaitFlags) ToOptions(args []string) (*WaitOptions, error) {
 	}
 
 	o := &WaitOptions{
-		ResourceFinder: builder,
-		DynamicClient:  dynamicClient,
-		Timeout:        effectiveTimeout,
-		ForCondition:   flags.ForCondition,
+		ResourceFinder:  builder,
+		DynamicClient:   dynamicClient,
+		Timeout:         effectiveTimeout,
+		ForCondition:    flags.ForCondition,
+		WaitForCreation: flags.WaitForCreation,
 
 		Printer:     printer,
 		ConditionFn: conditionFn,
@@ -302,10 +309,11 @@ type WaitOptions struct {
 	ResourceFinder genericclioptions.ResourceFinder
 	// UIDMap maps a resource location to a UID.  It is optional, but ConditionFuncs may choose to use it to make the result
 	// more reliable.  For instance, delete can look for UID consistency during delegated calls.
-	UIDMap        UIDMap
-	DynamicClient dynamic.Interface
-	Timeout       time.Duration
-	ForCondition  string
+	UIDMap          UIDMap
+	DynamicClient   dynamic.Interface
+	Timeout         time.Duration
+	ForCondition    string
+	WaitForCreation bool
 
 	Printer     printers.ResourcePrinter
 	ConditionFn ConditionFunc
@@ -320,6 +328,40 @@ func (o *WaitOptions) RunWait() error {
 	ctx, cancel := watchtools.ContextWithOptionalTimeout(context.Background(), o.Timeout)
 	defer cancel()
 
+	isForDelete := strings.ToLower(o.ForCondition) == "delete"
+	if o.WaitForCreation && o.Timeout == 0 {
+		return fmt.Errorf("--wait-for-creation requires a timeout value greater than 0")
+	}
+
+	if o.WaitForCreation && !isForDelete {
+		err := func() error {
+			for {
+				select {
+				case <-ctx.Done():
+					return fmt.Errorf("context deadline is exceeded while waiting for the creation of the resources")
+				default:
+					err := o.ResourceFinder.Do().Visit(func(info *resource.Info, err error) error {
+						// We don't need to do anything after we assure that the resources exist. Because
+						// actual logic will be incorporated after we wait all the resources' existence.
+						return nil
+					})
+					// It is verified that all the resources exist.
+					if err == nil {
+						return nil
+					}
+					// We specifically wait for the creation of resources and all the errors
+					// other than not found means that this is something we cannot handle.
+					if !apierrors.IsNotFound(err) {
+						return err
+					}
+				}
+			}
+		}()
+		if err != nil {
+			return err
+		}
+	}
+
 	visitCount := 0
 	visitFunc := func(info *resource.Info, err error) error {
 		if err != nil {
@@ -338,7 +380,6 @@ func (o *WaitOptions) RunWait() error {
 		return err
 	}
 	visitor := o.ResourceFinder.Do()
-	isForDelete := strings.ToLower(o.ForCondition) == "delete"
 	if visitor, ok := visitor.(*resource.Result); ok && isForDelete {
 		visitor.IgnoreErrors(apierrors.IsNotFound)
 	}

test/cmd/legacy-script.sh

@@ -1036,6 +1036,7 @@ runTests() {
   ####################
 
   record_command run_wait_tests
+  record_command run_wait_with_non_existence_check_tests
 
   ####################
   # kubectl debug    #

test/cmd/wait.sh

@@ -117,3 +117,106 @@ EOF
     set +o nounset
     set +o errexit
 }
+
+run_wait_with_non_existence_check_tests() {
+    set -o nounset
+    set -o errexit
+
+    kube::log::status "Testing kubectl wait"
+
+    create_and_use_new_namespace
+
+    ### Wait for deletion using --all flag
+
+    # create test data
+    kubectl create deployment test-1 --image=busybox
+    kubectl create deployment test-2 --image=busybox
+
+    # Post-Condition: deployments exists
+    kube::test::get_object_assert "deployments" "{{range .items}}{{.metadata.name}},{{end}}" 'test-1,test-2,'
+
+    # wait with jsonpath will timout for busybox deployment
+    set +o errexit
+    # Command: Wait with jsonpath support fields not exist in the first place
+    output_message=$(kubectl wait --wait-for-creation --for=jsonpath=.status.readyReplicas=1 deploy/test-1 2>&1)
+    set -o errexit
+
+    # Post-Condition: Wait failed
+    kube::test::if_has_string "${output_message}" 'timed out'
+
+    # Delete all deployments async to kubectl wait
+    ( sleep 2 && kubectl delete deployment --all ) &
+
+    # Command: Wait for all deployments to be deleted
+    output_message=$(kubectl wait deployment --for=delete --all)
+
+    # Post-Condition: Wait was successful
+    kube::test::if_has_string "${output_message}" 'test-1 condition met'
+    kube::test::if_has_string "${output_message}" 'test-2 condition met'
+
+    # create test data to test timeout error is occurred in correct time
+    kubectl apply -f - <<EOF
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app: dtest
+  name: dtest
+spec:
+  replicas: 3
+  selector:
+    matchLabels:
+      app: dtest
+  template:
+    metadata:
+      labels:
+        app: dtest
+    spec:
+      containers:
+      - name: bb
+        image: busybox
+        command: ["/bin/sh", "-c", "sleep infinity"]
+EOF
+
+    set +o errexit
+    # wait timeout error because condition is invalid
+    start_sec=$(date +"%s")
+    output_message=$(time kubectl wait pod --wait-for-creation --selector=app=dtest --for=condition=InvalidCondition --timeout=1s 2>&1)
+    end_sec=$(date +"%s")
+    len_sec=$((end_sec-start_sec))
+    set -o errexit
+    kube::test::if_has_string "${output_message}" 'timed out waiting for the condition '
+    test $len_sec -ge 1 && test $len_sec -le 2
+
+    # Clean deployment
+    kubectl delete deployment dtest
+
+    # create test data
+    kubectl create deployment test-3 --image=busybox
+
+    # wait with jsonpath without value to succeed
+    set +o errexit
+    # Command: Wait with jsonpath without value
+    output_message_0=$(kubectl wait --wait-for-creation --for=jsonpath='{.status.replicas}' deploy/test-3 2>&1)
+    # Command: Wait with relaxed jsonpath and filter expression
+    output_message_1=$(kubectl wait \
+        --for='jsonpath=spec.template.spec.containers[?(@.name=="busybox")].image=busybox' \
+        deploy/test-3)
+    set -o errexit
+
+    # Post-Condition: Wait succeed
+    kube::test::if_has_string "${output_message_0}" 'deployment.apps/test-3 condition met'
+    kube::test::if_has_string "${output_message_1}" 'deployment.apps/test-3 condition met'
+
+    # Clean deployment
+    kubectl delete deployment test-3
+
+    ( sleep 3 && kubectl create deployment test-4 --image=busybox ) &
+    output_message=$(kubectl wait --wait-for-creation --for=jsonpath=.status.replicas=1 deploy/test-4 2>&1)
+    kube::test::if_has_string "${output_message}" 'test-4 condition met'
+
+    kubectl delete deployment test-4
+
+    set +o nounset
+    set +o errexit
+}