mirror of https://github.com/k3s-io/k3s
288 lines
8.8 KiB
Go
288 lines
8.8 KiB
Go
/*
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Copyright 2017 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package watch
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import (
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"context"
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"errors"
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"fmt"
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"io"
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"net/http"
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"time"
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"github.com/davecgh/go-spew/spew"
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apierrors "k8s.io/apimachinery/pkg/api/errors"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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"k8s.io/apimachinery/pkg/util/net"
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"k8s.io/apimachinery/pkg/util/wait"
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"k8s.io/apimachinery/pkg/watch"
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"k8s.io/client-go/tools/cache"
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"k8s.io/klog"
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)
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// resourceVersionGetter is an interface used to get resource version from events.
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// We can't reuse an interface from meta otherwise it would be a cyclic dependency and we need just this one method
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type resourceVersionGetter interface {
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GetResourceVersion() string
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}
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// RetryWatcher will make sure that in case the underlying watcher is closed (e.g. due to API timeout or etcd timeout)
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// it will get restarted from the last point without the consumer even knowing about it.
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// RetryWatcher does that by inspecting events and keeping track of resourceVersion.
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// Especially useful when using watch.UntilWithoutRetry where premature termination is causing issues and flakes.
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// Please note that this is not resilient to etcd cache not having the resource version anymore - you would need to
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// use Informers for that.
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type RetryWatcher struct {
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lastResourceVersion string
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watcherClient cache.Watcher
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resultChan chan watch.Event
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stopChan chan struct{}
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doneChan chan struct{}
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minRestartDelay time.Duration
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}
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// NewRetryWatcher creates a new RetryWatcher.
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// It will make sure that watches gets restarted in case of recoverable errors.
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// The initialResourceVersion will be given to watch method when first called.
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func NewRetryWatcher(initialResourceVersion string, watcherClient cache.Watcher) (*RetryWatcher, error) {
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return newRetryWatcher(initialResourceVersion, watcherClient, 1*time.Second)
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}
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func newRetryWatcher(initialResourceVersion string, watcherClient cache.Watcher, minRestartDelay time.Duration) (*RetryWatcher, error) {
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switch initialResourceVersion {
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case "", "0":
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// TODO: revisit this if we ever get WATCH v2 where it means start "now"
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// without doing the synthetic list of objects at the beginning (see #74022)
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return nil, fmt.Errorf("initial RV %q is not supported due to issues with underlying WATCH", initialResourceVersion)
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default:
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break
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}
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rw := &RetryWatcher{
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lastResourceVersion: initialResourceVersion,
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watcherClient: watcherClient,
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stopChan: make(chan struct{}),
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doneChan: make(chan struct{}),
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resultChan: make(chan watch.Event, 0),
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minRestartDelay: minRestartDelay,
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}
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go rw.receive()
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return rw, nil
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}
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func (rw *RetryWatcher) send(event watch.Event) bool {
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// Writing to an unbuffered channel is blocking operation
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// and we need to check if stop wasn't requested while doing so.
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select {
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case rw.resultChan <- event:
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return true
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case <-rw.stopChan:
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return false
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}
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}
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// doReceive returns true when it is done, false otherwise.
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// If it is not done the second return value holds the time to wait before calling it again.
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func (rw *RetryWatcher) doReceive() (bool, time.Duration) {
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watcher, err := rw.watcherClient.Watch(metav1.ListOptions{
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ResourceVersion: rw.lastResourceVersion,
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})
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// We are very unlikely to hit EOF here since we are just establishing the call,
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// but it may happen that the apiserver is just shutting down (e.g. being restarted)
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// This is consistent with how it is handled for informers
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switch err {
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case nil:
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break
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case io.EOF:
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// watch closed normally
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return false, 0
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case io.ErrUnexpectedEOF:
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klog.V(1).Infof("Watch closed with unexpected EOF: %v", err)
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return false, 0
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default:
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msg := "Watch failed: %v"
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if net.IsProbableEOF(err) {
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klog.V(5).Infof(msg, err)
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// Retry
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return false, 0
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}
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klog.Errorf(msg, err)
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// Retry
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return false, 0
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}
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if watcher == nil {
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klog.Error("Watch returned nil watcher")
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// Retry
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return false, 0
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}
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ch := watcher.ResultChan()
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defer watcher.Stop()
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for {
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select {
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case <-rw.stopChan:
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klog.V(4).Info("Stopping RetryWatcher.")
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return true, 0
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case event, ok := <-ch:
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if !ok {
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klog.V(4).Infof("Failed to get event! Re-creating the watcher. Last RV: %s", rw.lastResourceVersion)
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return false, 0
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}
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// We need to inspect the event and get ResourceVersion out of it
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switch event.Type {
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case watch.Added, watch.Modified, watch.Deleted, watch.Bookmark:
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metaObject, ok := event.Object.(resourceVersionGetter)
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if !ok {
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_ = rw.send(watch.Event{
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Type: watch.Error,
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Object: &apierrors.NewInternalError(errors.New("retryWatcher: doesn't support resourceVersion")).ErrStatus,
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})
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// We have to abort here because this might cause lastResourceVersion inconsistency by skipping a potential RV with valid data!
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return true, 0
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}
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resourceVersion := metaObject.GetResourceVersion()
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if resourceVersion == "" {
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_ = rw.send(watch.Event{
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Type: watch.Error,
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Object: &apierrors.NewInternalError(fmt.Errorf("retryWatcher: object %#v doesn't support resourceVersion", event.Object)).ErrStatus,
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})
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// We have to abort here because this might cause lastResourceVersion inconsistency by skipping a potential RV with valid data!
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return true, 0
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}
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// All is fine; send the event and update lastResourceVersion
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ok = rw.send(event)
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if !ok {
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return true, 0
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}
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rw.lastResourceVersion = resourceVersion
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continue
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case watch.Error:
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// This round trip allows us to handle unstructured status
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errObject := apierrors.FromObject(event.Object)
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statusErr, ok := errObject.(*apierrors.StatusError)
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if !ok {
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klog.Error(spew.Sprintf("Received an error which is not *metav1.Status but %#+v", event.Object))
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// Retry unknown errors
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return false, 0
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}
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status := statusErr.ErrStatus
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statusDelay := time.Duration(0)
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if status.Details != nil {
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statusDelay = time.Duration(status.Details.RetryAfterSeconds) * time.Second
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}
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switch status.Code {
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case http.StatusGone:
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// Never retry RV too old errors
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_ = rw.send(event)
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return true, 0
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case http.StatusGatewayTimeout, http.StatusInternalServerError:
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// Retry
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return false, statusDelay
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default:
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// We retry by default. RetryWatcher is meant to proceed unless it is certain
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// that it can't. If we are not certain, we proceed with retry and leave it
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// up to the user to timeout if needed.
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// Log here so we have a record of hitting the unexpected error
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// and we can whitelist some error codes if we missed any that are expected.
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klog.V(5).Info(spew.Sprintf("Retrying after unexpected error: %#+v", event.Object))
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// Retry
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return false, statusDelay
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}
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default:
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klog.Errorf("Failed to recognize Event type %q", event.Type)
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_ = rw.send(watch.Event{
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Type: watch.Error,
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Object: &apierrors.NewInternalError(fmt.Errorf("retryWatcher failed to recognize Event type %q", event.Type)).ErrStatus,
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})
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// We are unable to restart the watch and have to stop the loop or this might cause lastResourceVersion inconsistency by skipping a potential RV with valid data!
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return true, 0
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}
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}
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}
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}
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// receive reads the result from a watcher, restarting it if necessary.
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func (rw *RetryWatcher) receive() {
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defer close(rw.doneChan)
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defer close(rw.resultChan)
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klog.V(4).Info("Starting RetryWatcher.")
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defer klog.V(4).Info("Stopping RetryWatcher.")
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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go func() {
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select {
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case <-rw.stopChan:
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cancel()
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return
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case <-ctx.Done():
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return
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}
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}()
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// We use non sliding until so we don't introduce delays on happy path when WATCH call
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// timeouts or gets closed and we need to reestablish it while also avoiding hot loops.
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wait.NonSlidingUntilWithContext(ctx, func(ctx context.Context) {
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done, retryAfter := rw.doReceive()
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if done {
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cancel()
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return
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}
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time.Sleep(retryAfter)
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klog.V(4).Infof("Restarting RetryWatcher at RV=%q", rw.lastResourceVersion)
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}, rw.minRestartDelay)
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}
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// ResultChan implements Interface.
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func (rw *RetryWatcher) ResultChan() <-chan watch.Event {
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return rw.resultChan
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}
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// Stop implements Interface.
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func (rw *RetryWatcher) Stop() {
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close(rw.stopChan)
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}
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// Done allows the caller to be notified when Retry watcher stops.
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func (rw *RetryWatcher) Done() <-chan struct{} {
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return rw.doneChan
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}
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