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wait.go
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wait.go
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/*
Copyright 2018 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package wait
import (
"context"
"errors"
"fmt"
"io"
"strings"
"time"
"github.com/spf13/cobra"
apierrors "k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
"k8s.io/apimachinery/pkg/fields"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/runtime/schema"
"k8s.io/apimachinery/pkg/types"
"k8s.io/apimachinery/pkg/util/wait"
"k8s.io/apimachinery/pkg/watch"
"k8s.io/cli-runtime/pkg/genericclioptions"
"k8s.io/cli-runtime/pkg/printers"
"k8s.io/cli-runtime/pkg/resource"
"k8s.io/client-go/dynamic"
watchtools "k8s.io/client-go/tools/watch"
cmdutil "k8s.io/kubectl/pkg/cmd/util"
"k8s.io/kubectl/pkg/util/i18n"
"k8s.io/kubectl/pkg/util/templates"
)
var (
waitLong = templates.LongDesc(i18n.T(`
Experimental: Wait for a specific condition on one or many resources.
The command takes multiple resources and waits until the specified condition
is seen in the Status field of every given resource.
Alternatively, the command can wait for the given set of resources to be deleted
by providing the "delete" keyword as the value to the --for flag.
A successful message will be printed to stdout indicating when the specified
condition has been met. You can use -o option to change to output destination.`))
waitExample = templates.Examples(i18n.T(`
# Wait for the pod "busybox1" to contain the status condition of type "Ready"
kubectl wait --for=condition=Ready pod/busybox1
# The default value of status condition is true; you can set it to false
kubectl wait --for=condition=Ready=false pod/busybox1
# 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`))
)
// errNoMatchingResources is returned when there is no resources matching a query.
var errNoMatchingResources = errors.New("no matching resources found")
// WaitFlags directly reflect the information that CLI is gathering via flags. They will be converted to Options, which
// reflect the runtime requirements for the command. This structure reduces the transformation to wiring and makes
// the logic itself easy to unit test
type WaitFlags struct {
RESTClientGetter genericclioptions.RESTClientGetter
PrintFlags *genericclioptions.PrintFlags
ResourceBuilderFlags *genericclioptions.ResourceBuilderFlags
Timeout time.Duration
ForCondition string
genericclioptions.IOStreams
}
// NewWaitFlags returns a default WaitFlags
func NewWaitFlags(restClientGetter genericclioptions.RESTClientGetter, streams genericclioptions.IOStreams) *WaitFlags {
return &WaitFlags{
RESTClientGetter: restClientGetter,
PrintFlags: genericclioptions.NewPrintFlags("condition met"),
ResourceBuilderFlags: genericclioptions.NewResourceBuilderFlags().
WithLabelSelector("").
WithFieldSelector("").
WithAll(false).
WithAllNamespaces(false).
WithLocal(false).
WithLatest(),
Timeout: 30 * time.Second,
IOStreams: streams,
}
}
// NewCmdWait returns a cobra command for waiting
func NewCmdWait(restClientGetter genericclioptions.RESTClientGetter, streams genericclioptions.IOStreams) *cobra.Command {
flags := NewWaitFlags(restClientGetter, streams)
cmd := &cobra.Command{
Use: "wait ([-f FILENAME] | resource.group/resource.name | resource.group [(-l label | --all)]) [--for=delete|--for condition=available]",
Short: i18n.T("Experimental: Wait for a specific condition on one or many resources"),
Long: waitLong,
Example: waitExample,
DisableFlagsInUseLine: true,
Run: func(cmd *cobra.Command, args []string) {
o, err := flags.ToOptions(args)
cmdutil.CheckErr(err)
cmdutil.CheckErr(o.RunWait())
},
SuggestFor: []string{"list", "ps"},
}
flags.AddFlags(cmd)
return cmd
}
// AddFlags registers flags for a cli
func (flags *WaitFlags) AddFlags(cmd *cobra.Command) {
flags.PrintFlags.AddFlags(cmd)
flags.ResourceBuilderFlags.AddFlags(cmd.Flags())
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]. The default status value of condition-name is true, you can set false with condition=condition-name=false")
}
// ToOptions converts from CLI inputs to runtime inputs
func (flags *WaitFlags) ToOptions(args []string) (*WaitOptions, error) {
printer, err := flags.PrintFlags.ToPrinter()
if err != nil {
return nil, err
}
builder := flags.ResourceBuilderFlags.ToBuilder(flags.RESTClientGetter, args)
clientConfig, err := flags.RESTClientGetter.ToRESTConfig()
if err != nil {
return nil, err
}
dynamicClient, err := dynamic.NewForConfig(clientConfig)
if err != nil {
return nil, err
}
conditionFn, err := conditionFuncFor(flags.ForCondition, flags.ErrOut)
if err != nil {
return nil, err
}
effectiveTimeout := flags.Timeout
if effectiveTimeout < 0 {
effectiveTimeout = 168 * time.Hour
}
o := &WaitOptions{
ResourceFinder: builder,
DynamicClient: dynamicClient,
Timeout: effectiveTimeout,
ForCondition: flags.ForCondition,
Printer: printer,
ConditionFn: conditionFn,
IOStreams: flags.IOStreams,
}
return o, nil
}
func conditionFuncFor(condition string, errOut io.Writer) (ConditionFunc, error) {
if strings.ToLower(condition) == "delete" {
return IsDeleted, nil
}
if strings.HasPrefix(condition, "condition=") {
conditionName := condition[len("condition="):]
conditionValue := "true"
if equalsIndex := strings.Index(conditionName, "="); equalsIndex != -1 {
conditionValue = conditionName[equalsIndex+1:]
conditionName = conditionName[0:equalsIndex]
}
return ConditionalWait{
conditionName: conditionName,
conditionStatus: conditionValue,
errOut: errOut,
}.IsConditionMet, nil
}
return nil, fmt.Errorf("unrecognized condition: %q", condition)
}
// ResourceLocation holds the location of a resource
type ResourceLocation struct {
GroupResource schema.GroupResource
Namespace string
Name string
}
// UIDMap maps ResourceLocation with UID
type UIDMap map[ResourceLocation]types.UID
// WaitOptions is a set of options that allows you to wait. This is the object reflects the runtime needs of a wait
// command, making the logic itself easy to unit test with our existing mocks.
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
Printer printers.ResourcePrinter
ConditionFn ConditionFunc
genericclioptions.IOStreams
}
// ConditionFunc is the interface for providing condition checks
type ConditionFunc func(info *resource.Info, o *WaitOptions) (finalObject runtime.Object, done bool, err error)
// RunWait runs the waiting logic
func (o *WaitOptions) RunWait() error {
visitCount := 0
visitFunc := func(info *resource.Info, err error) error {
if err != nil {
return err
}
visitCount++
finalObject, success, err := o.ConditionFn(info, o)
if success {
o.Printer.PrintObj(finalObject, o.Out)
return nil
}
if err == nil {
return fmt.Errorf("%v unsatisified for unknown reason", finalObject)
}
return err
}
visitor := o.ResourceFinder.Do()
isForDelete := strings.ToLower(o.ForCondition) == "delete"
if visitor, ok := visitor.(*resource.Result); ok && isForDelete {
visitor.IgnoreErrors(apierrors.IsNotFound)
}
err := visitor.Visit(visitFunc)
if err != nil {
return err
}
if visitCount == 0 && !isForDelete {
return errNoMatchingResources
}
return err
}
// IsDeleted is a condition func for waiting for something to be deleted
func IsDeleted(info *resource.Info, o *WaitOptions) (runtime.Object, bool, error) {
endTime := time.Now().Add(o.Timeout)
for {
if len(info.Name) == 0 {
return info.Object, false, fmt.Errorf("resource name must be provided")
}
nameSelector := fields.OneTermEqualSelector("metadata.name", info.Name).String()
// List with a name field selector to get the current resourceVersion to watch from (not the object's resourceVersion)
gottenObjList, err := o.DynamicClient.Resource(info.Mapping.Resource).Namespace(info.Namespace).List(context.TODO(), metav1.ListOptions{FieldSelector: nameSelector})
if apierrors.IsNotFound(err) {
return info.Object, true, nil
}
if err != nil {
// TODO this could do something slightly fancier if we wish
return info.Object, false, err
}
if len(gottenObjList.Items) != 1 {
return info.Object, true, nil
}
gottenObj := &gottenObjList.Items[0]
resourceLocation := ResourceLocation{
GroupResource: info.Mapping.Resource.GroupResource(),
Namespace: gottenObj.GetNamespace(),
Name: gottenObj.GetName(),
}
if uid, ok := o.UIDMap[resourceLocation]; ok {
if gottenObj.GetUID() != uid {
return gottenObj, true, nil
}
}
watchOptions := metav1.ListOptions{}
watchOptions.FieldSelector = nameSelector
watchOptions.ResourceVersion = gottenObjList.GetResourceVersion()
objWatch, err := o.DynamicClient.Resource(info.Mapping.Resource).Namespace(info.Namespace).Watch(context.TODO(), watchOptions)
if err != nil {
return gottenObj, false, err
}
timeout := endTime.Sub(time.Now())
errWaitTimeoutWithName := extendErrWaitTimeout(wait.ErrWaitTimeout, info)
if timeout < 0 {
// we're out of time
return gottenObj, false, errWaitTimeoutWithName
}
ctx, cancel := watchtools.ContextWithOptionalTimeout(context.Background(), o.Timeout)
watchEvent, err := watchtools.UntilWithoutRetry(ctx, objWatch, Wait{errOut: o.ErrOut}.IsDeleted)
cancel()
switch {
case err == nil:
return watchEvent.Object, true, nil
case err == watchtools.ErrWatchClosed:
continue
case err == wait.ErrWaitTimeout:
if watchEvent != nil {
return watchEvent.Object, false, errWaitTimeoutWithName
}
return gottenObj, false, errWaitTimeoutWithName
default:
return gottenObj, false, err
}
}
}
// Wait has helper methods for handling watches, including error handling.
type Wait struct {
errOut io.Writer
}
// IsDeleted returns true if the object is deleted. It prints any errors it encounters.
func (w Wait) IsDeleted(event watch.Event) (bool, error) {
switch event.Type {
case watch.Error:
// keep waiting in the event we see an error - we expect the watch to be closed by
// the server if the error is unrecoverable.
err := apierrors.FromObject(event.Object)
fmt.Fprintf(w.errOut, "error: An error occurred while waiting for the object to be deleted: %v", err)
return false, nil
case watch.Deleted:
return true, nil
default:
return false, nil
}
}
// ConditionalWait hold information to check an API status condition
type ConditionalWait struct {
conditionName string
conditionStatus string
// errOut is written to if an error occurs
errOut io.Writer
}
// IsConditionMet is a conditionfunc for waiting on an API condition to be met
func (w ConditionalWait) IsConditionMet(info *resource.Info, o *WaitOptions) (runtime.Object, bool, error) {
endTime := time.Now().Add(o.Timeout)
for {
if len(info.Name) == 0 {
return info.Object, false, fmt.Errorf("resource name must be provided")
}
nameSelector := fields.OneTermEqualSelector("metadata.name", info.Name).String()
var gottenObj *unstructured.Unstructured
// List with a name field selector to get the current resourceVersion to watch from (not the object's resourceVersion)
gottenObjList, err := o.DynamicClient.Resource(info.Mapping.Resource).Namespace(info.Namespace).List(context.TODO(), metav1.ListOptions{FieldSelector: nameSelector})
resourceVersion := ""
switch {
case err != nil:
return info.Object, false, err
case len(gottenObjList.Items) != 1:
resourceVersion = gottenObjList.GetResourceVersion()
default:
gottenObj = &gottenObjList.Items[0]
conditionMet, err := w.checkCondition(gottenObj)
if conditionMet {
return gottenObj, true, nil
}
if err != nil {
return gottenObj, false, err
}
resourceVersion = gottenObjList.GetResourceVersion()
}
watchOptions := metav1.ListOptions{}
watchOptions.FieldSelector = nameSelector
watchOptions.ResourceVersion = resourceVersion
objWatch, err := o.DynamicClient.Resource(info.Mapping.Resource).Namespace(info.Namespace).Watch(context.TODO(), watchOptions)
if err != nil {
return gottenObj, false, err
}
timeout := endTime.Sub(time.Now())
errWaitTimeoutWithName := extendErrWaitTimeout(wait.ErrWaitTimeout, info)
if timeout < 0 {
// we're out of time
return gottenObj, false, errWaitTimeoutWithName
}
ctx, cancel := watchtools.ContextWithOptionalTimeout(context.Background(), o.Timeout)
watchEvent, err := watchtools.UntilWithoutRetry(ctx, objWatch, w.isConditionMet)
cancel()
switch {
case err == nil:
return watchEvent.Object, true, nil
case err == watchtools.ErrWatchClosed:
continue
case err == wait.ErrWaitTimeout:
if watchEvent != nil {
return watchEvent.Object, false, errWaitTimeoutWithName
}
return gottenObj, false, errWaitTimeoutWithName
default:
return gottenObj, false, err
}
}
}
func (w ConditionalWait) checkCondition(obj *unstructured.Unstructured) (bool, error) {
conditions, found, err := unstructured.NestedSlice(obj.Object, "status", "conditions")
if err != nil {
return false, err
}
if !found {
return false, nil
}
for _, conditionUncast := range conditions {
condition := conditionUncast.(map[string]interface{})
name, found, err := unstructured.NestedString(condition, "type")
if !found || err != nil || !strings.EqualFold(name, w.conditionName) {
continue
}
status, found, err := unstructured.NestedString(condition, "status")
if !found || err != nil {
continue
}
generation, found, _ := unstructured.NestedInt64(obj.Object, "metadata", "generation")
if found {
observedGeneration, found := getObservedGeneration(obj, condition)
if found && observedGeneration < generation {
return false, nil
}
}
return strings.EqualFold(status, w.conditionStatus), nil
}
return false, nil
}
func (w ConditionalWait) isConditionMet(event watch.Event) (bool, error) {
if event.Type == watch.Error {
// keep waiting in the event we see an error - we expect the watch to be closed by
// the server
err := apierrors.FromObject(event.Object)
fmt.Fprintf(w.errOut, "error: An error occurred while waiting for the condition to be satisfied: %v", err)
return false, nil
}
if event.Type == watch.Deleted {
// this will chain back out, result in another get and an return false back up the chain
return false, nil
}
obj := event.Object.(*unstructured.Unstructured)
return w.checkCondition(obj)
}
func extendErrWaitTimeout(err error, info *resource.Info) error {
return fmt.Errorf("%s on %s/%s", err.Error(), info.Mapping.Resource.Resource, info.Name)
}
func getObservedGeneration(obj *unstructured.Unstructured, condition map[string]interface{}) (int64, bool) {
conditionObservedGeneration, found, _ := unstructured.NestedInt64(condition, "observedGeneration")
if found {
return conditionObservedGeneration, true
}
statusObservedGeneration, found, _ := unstructured.NestedInt64(obj.Object, "status", "observedGeneration")
return statusObservedGeneration, found
}