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plugin/kubernetes: do endpoint/slice check in retry loop (#4492)

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* do endpoint/slice check in retry loop

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>
This commit is contained in:
Chris O'Haver 2021-03-26 08:54:39 -04:00 • committed by GitHub
parent ea41dd23a0
commit 9f72db12e7
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4 changed files with 141 additions and 74 deletions
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97
plugin/kubernetes/kubernetes.go
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@ -8,6 +8,7 @@ import (
"net"
"strconv"
"strings"
"time"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/etcd/msg"
@ -213,22 +214,22 @@ func (k *Kubernetes) getClientConfig() (*rest.Config, error) {
}
// InitKubeCache initializes a new Kubernetes cache.
func (k *Kubernetes) InitKubeCache(ctx context.Context) (err error) {
func (k *Kubernetes) InitKubeCache(ctx context.Context) (onStart func() error, onShut func() error, err error) {
config, err := k.getClientConfig()
if err != nil {
return err
return nil, nil, err
}
kubeClient, err := kubernetes.NewForConfig(config)
if err != nil {
return fmt.Errorf("failed to create kubernetes notification controller: %q", err)
return nil, nil, fmt.Errorf("failed to create kubernetes notification controller: %q", err)
}
if k.opts.labelSelector != nil {
var selector labels.Selector
selector, err = meta.LabelSelectorAsSelector(k.opts.labelSelector)
if err != nil {
return fmt.Errorf("unable to create Selector for LabelSelector '%s': %q", k.opts.labelSelector, err)
return nil, nil, fmt.Errorf("unable to create Selector for LabelSelector '%s': %q", k.opts.labelSelector, err)
}
k.opts.selector = selector
}
@ -237,7 +238,7 @@ func (k *Kubernetes) InitKubeCache(ctx context.Context) (err error) {
var selector labels.Selector
selector, err = meta.LabelSelectorAsSelector(k.opts.namespaceLabelSelector)
if err != nil {
return fmt.Errorf("unable to create Selector for LabelSelector '%s': %q", k.opts.namespaceLabelSelector, err)
return nil, nil, fmt.Errorf("unable to create Selector for LabelSelector '%s': %q", k.opts.namespaceLabelSelector, err)
}
k.opts.namespaceSelector = selector
}
@ -246,25 +247,79 @@ func (k *Kubernetes) InitKubeCache(ctx context.Context) (err error) {
k.opts.zones = k.Zones
k.opts.endpointNameMode = k.endpointNameMode
// Enable use of endpoint slices if the API supports the discovery v1 beta1 api
if _, err := kubeClient.Discovery().ServerResourcesForGroupVersion(discovery.SchemeGroupVersion.String()); err == nil {
k.opts.useEndpointSlices = true
}
// Disable use of endpoint slices for k8s versions 1.18 and earlier. Endpoint slices were
// introduced in 1.17 but EndpointSliceMirroring was not added until 1.19.
// if err != nil, we continue with the above default which is to use endpoint slices.
if sv, err := kubeClient.ServerVersion(); err == nil {
major, _ := strconv.Atoi(sv.Major)
minor, _ := strconv.Atoi(strings.TrimRight(sv.Minor, "+"))
if k.opts.useEndpointSlices && major <= 1 && minor <= 18 {
log.Info("Watching Endpoints instead of EndpointSlices in k8s versions < 1.19")
k.opts.useEndpointSlices = false
}
}
k.APIConn = newdnsController(ctx, kubeClient, k.opts)
return err
initEndpointWatch := k.opts.initEndpointsCache
onStart = func() error {
go func() {
if initEndpointWatch {
// Revert to watching Endpoints for incompatible K8s.
// This can be remove when all supported k8s versions support endpointslices.
if ok := k.endpointSliceSupported(kubeClient); !ok {
k.APIConn.(*dnsControl).WatchEndpoints(ctx)
}
}
k.APIConn.Run()
}()
timeout := time.After(5 * time.Second)
ticker := time.NewTicker(100 * time.Millisecond)
defer ticker.Stop()
for {
select {
case <-ticker.C:
if k.APIConn.HasSynced() {
return nil
}
case <-timeout:
log.Warning("starting server with unsynced Kubernetes API")
return nil
}
}
}
onShut = func() error {
return k.APIConn.Stop()
}
return onStart, onShut, err
}
// endpointSliceSupported will determine which endpoint object type to watch (endpointslices or endpoints)
// based on the supportability of endpointslices in the API and server version. It will return true when endpointslices
// should be watched, and false when endpoints should be watched.
// If the API supports discovery v1 beta1, and the server versions >= 1.19, endpointslices are watched.
// This function should be removed, along with non-slice endpoint watch code, when support for k8s < 1.19 is dropped.
func (k *Kubernetes) endpointSliceSupported(kubeClient *kubernetes.Clientset) bool {
useEndpointSlices := false
ticker := time.NewTicker(100 * time.Millisecond)
defer ticker.Stop()
for {
select {
case <-ticker.C:
sv, err := kubeClient.ServerVersion()
if err != nil {
continue
}
// Enable use of endpoint slices if the API supports the discovery v1 beta1 api
if _, err := kubeClient.Discovery().ServerResourcesForGroupVersion(discovery.SchemeGroupVersion.String()); err == nil {
useEndpointSlices = true
}
// Disable use of endpoint slices for k8s versions 1.18 and earlier. The Endpointslices API was enabled
// by default in 1.17 but Service -> Pod proxy continued to use Endpoints by default until 1.19.
// DNS results should be built from the same source data that the proxy uses. This decision assumes
// k8s EndpointSliceProxying featuregate is at the default (i.e. only enabled for k8s >= 1.19).
major, _ := strconv.Atoi(sv.Major)
minor, _ := strconv.Atoi(strings.TrimRight(sv.Minor, "+"))
if useEndpointSlices && major <= 1 && minor <= 18 {
log.Info("Watching Endpoints instead of EndpointSlices in k8s versions < 1.19")
useEndpointSlices = false
}
return useEndpointSlices
}
}
}
// Records looks up services in kubernetes.