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kind.go
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kind.go
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package internal
import (
"context"
"errors"
"fmt"
"reflect"
"time"
"k8s.io/apimachinery/pkg/api/meta"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/util/wait"
"k8s.io/client-go/util/workqueue"
"sigs.k8s.io/controller-runtime/pkg/cache"
"sigs.k8s.io/controller-runtime/pkg/client"
"sigs.k8s.io/controller-runtime/pkg/handler"
"sigs.k8s.io/controller-runtime/pkg/predicate"
)
// Kind is used to provide a source of events originating inside the cluster from Watches (e.g. Pod Create).
type Kind[T client.Object] struct {
// Type is the type of object to watch. e.g. &v1.Pod{}
Type T
// Cache used to watch APIs
Cache cache.Cache
Handler handler.TypedEventHandler[T]
Predicates []predicate.TypedPredicate[T]
// startedErr may contain an error if one was encountered during startup. If its closed and does not
// contain an error, startup and syncing finished.
startedErr chan error
startCancel func()
}
// Start is internal and should be called only by the Controller to register an EventHandler with the Informer
// to enqueue reconcile.Requests.
func (ks *Kind[T]) Start(ctx context.Context, queue workqueue.RateLimitingInterface) error {
if isNil(ks.Type) {
return fmt.Errorf("must create Kind with a non-nil object")
}
if isNil(ks.Cache) {
return fmt.Errorf("must create Kind with a non-nil cache")
}
if isNil(ks.Handler) {
return errors.New("must create Kind with non-nil handler")
}
// cache.GetInformer will block until its context is cancelled if the cache was already started and it can not
// sync that informer (most commonly due to RBAC issues).
ctx, ks.startCancel = context.WithCancel(ctx)
ks.startedErr = make(chan error)
go func() {
var (
i cache.Informer
lastErr error
)
// Tries to get an informer until it returns true,
// an error or the specified context is cancelled or expired.
if err := wait.PollUntilContextCancel(ctx, 10*time.Second, true, func(ctx context.Context) (bool, error) {
// Lookup the Informer from the Cache and add an EventHandler which populates the Queue
i, lastErr = ks.Cache.GetInformer(ctx, ks.Type)
if lastErr != nil {
kindMatchErr := &meta.NoKindMatchError{}
switch {
case errors.As(lastErr, &kindMatchErr):
log.Error(lastErr, "if kind is a CRD, it should be installed before calling Start",
"kind", kindMatchErr.GroupKind)
case runtime.IsNotRegisteredError(lastErr):
log.Error(lastErr, "kind must be registered to the Scheme")
default:
log.Error(lastErr, "failed to get informer from cache")
}
return false, nil // Retry.
}
return true, nil
}); err != nil {
if lastErr != nil {
ks.startedErr <- fmt.Errorf("failed to get informer from cache: %w", lastErr)
return
}
ks.startedErr <- err
return
}
_, err := i.AddEventHandler(NewEventHandler(ctx, queue, ks.Handler, ks.Predicates).HandlerFuncs())
if err != nil {
ks.startedErr <- err
return
}
if !ks.Cache.WaitForCacheSync(ctx) {
// Would be great to return something more informative here
ks.startedErr <- errors.New("cache did not sync")
}
close(ks.startedErr)
}()
return nil
}
func (ks *Kind[T]) String() string {
if isNil(ks.Type) {
return fmt.Sprintf("kind source: %T", ks.Type)
}
return "kind source: unknown type"
}
// WaitForSync implements SyncingSource to allow controllers to wait with starting
// workers until the cache is synced.
func (ks *Kind[T]) WaitForSync(ctx context.Context) error {
select {
case err := <-ks.startedErr:
return err
case <-ctx.Done():
ks.startCancel()
if errors.Is(ctx.Err(), context.Canceled) {
return nil
}
return fmt.Errorf("timed out waiting for cache to be synced for Kind %T", ks.Type)
}
}
func isNil(arg any) bool {
if v := reflect.ValueOf(arg); !v.IsValid() || ((v.Kind() == reflect.Ptr ||
v.Kind() == reflect.Interface ||
v.Kind() == reflect.Slice ||
v.Kind() == reflect.Map ||
v.Kind() == reflect.Chan ||
v.Kind() == reflect.Func) && v.IsNil()) {
return true
}
return false
}