system_namespaces_controller.go

Documentation: k8s.io/kubernetes/pkg/controlplane/controller/systemnamespaces

     1  /*
     2  Copyright 2023 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package systemnamespaces
    18  
    19  import (
    20  	"context"
    21  	"fmt"
    22  	"time"
    23  
    24  	v1 "k8s.io/api/core/v1"
    25  	"k8s.io/apimachinery/pkg/api/errors"
    26  	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    27  	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
    28  	"k8s.io/apimachinery/pkg/util/wait"
    29  	coreinformers "k8s.io/client-go/informers/core/v1"
    30  	"k8s.io/client-go/kubernetes"
    31  	listers "k8s.io/client-go/listers/core/v1"
    32  	"k8s.io/client-go/tools/cache"
    33  
    34  	"k8s.io/klog/v2"
    35  )
    36  
    37  // Controller ensure system namespaces exist.
    38  type Controller struct {
    39  	client kubernetes.Interface
    40  
    41  	namespaceLister listers.NamespaceLister
    42  	namespaceSynced cache.InformerSynced
    43  
    44  	systemNamespaces []string
    45  	interval         time.Duration
    46  }
    47  
    48  // NewController creates a new Controller to ensure system namespaces exist.
    49  func NewController(clientset kubernetes.Interface, namespaceInformer coreinformers.NamespaceInformer) *Controller {
    50  	systemNamespaces := []string{metav1.NamespaceSystem, metav1.NamespacePublic, v1.NamespaceNodeLease, metav1.NamespaceDefault}
    51  	interval := 1 * time.Minute
    52  
    53  	return &Controller{
    54  		client:           clientset,
    55  		namespaceLister:  namespaceInformer.Lister(),
    56  		namespaceSynced:  namespaceInformer.Informer().HasSynced,
    57  		systemNamespaces: systemNamespaces,
    58  		interval:         interval,
    59  	}
    60  }
    61  
    62  // Run starts one worker.
    63  func (c *Controller) Run(stopCh <-chan struct{}) {
    64  	defer utilruntime.HandleCrash()
    65  	defer klog.Infof("Shutting down system namespaces controller")
    66  
    67  	klog.Infof("Starting system namespaces controller")
    68  
    69  	if !cache.WaitForCacheSync(stopCh, c.namespaceSynced) {
    70  		utilruntime.HandleError(fmt.Errorf("timed out waiting for caches to sync"))
    71  		return
    72  	}
    73  
    74  	go wait.Until(c.sync, c.interval, stopCh)
    75  
    76  	<-stopCh
    77  }
    78  
    79  func (c *Controller) sync() {
    80  	// Loop the system namespace list, and create them if they do not exist
    81  	for _, ns := range c.systemNamespaces {
    82  		if err := c.createNamespaceIfNeeded(ns); err != nil {
    83  			utilruntime.HandleError(fmt.Errorf("unable to create required kubernetes system Namespace %s: %v", ns, err))
    84  		}
    85  	}
    86  }
    87  
    88  func (c *Controller) createNamespaceIfNeeded(ns string) error {
    89  	if _, err := c.namespaceLister.Get(ns); err == nil {
    90  		// the namespace already exists
    91  		return nil
    92  	}
    93  	newNs := &v1.Namespace{
    94  		ObjectMeta: metav1.ObjectMeta{
    95  			Name:      ns,
    96  			Namespace: "",
    97  		},
    98  	}
    99  	_, err := c.client.CoreV1().Namespaces().Create(context.TODO(), newNs, metav1.CreateOptions{})
   100  	if err != nil && errors.IsAlreadyExists(err) {
   101  		err = nil
   102  	}
   103  	return err
   104  }
   105
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