k8s.io/apiserver@v0.31.1/pkg/admission/handler.go (about)

     1  /*
     2  Copyright 2015 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 admission
    18  
    19  import (
    20  	"time"
    21  
    22  	"k8s.io/apimachinery/pkg/util/sets"
    23  )
    24  
    25  const (
    26  	// timeToWaitForReady is the amount of time to wait to let an admission controller to be ready to satisfy a request.
    27  	// this is useful when admission controllers need to warm their caches before letting requests through.
    28  	timeToWaitForReady = 10 * time.Second
    29  )
    30  
    31  // ReadyFunc is a function that returns true if the admission controller is ready to handle requests.
    32  type ReadyFunc func() bool
    33  
    34  // Handler is a base for admission control handlers that
    35  // support a predefined set of operations
    36  type Handler struct {
    37  	operations sets.String
    38  	readyFunc  ReadyFunc
    39  }
    40  
    41  // Handles returns true for methods that this handler supports
    42  func (h *Handler) Handles(operation Operation) bool {
    43  	return h.operations.Has(string(operation))
    44  }
    45  
    46  // NewHandler creates a new base handler that handles the passed
    47  // in operations
    48  func NewHandler(ops ...Operation) *Handler {
    49  	operations := sets.NewString()
    50  	for _, op := range ops {
    51  		operations.Insert(string(op))
    52  	}
    53  	return &Handler{
    54  		operations: operations,
    55  	}
    56  }
    57  
    58  // SetReadyFunc allows late registration of a ReadyFunc to know if the handler is ready to process requests.
    59  func (h *Handler) SetReadyFunc(readyFunc ReadyFunc) {
    60  	h.readyFunc = readyFunc
    61  }
    62  
    63  // WaitForReady will wait for the readyFunc (if registered) to return ready, and in case of timeout, will return false.
    64  func (h *Handler) WaitForReady() bool {
    65  	// there is no ready func configured, so we return immediately
    66  	if h.readyFunc == nil {
    67  		return true
    68  	}
    69  
    70  	timeout := time.After(timeToWaitForReady)
    71  	for !h.readyFunc() {
    72  		select {
    73  		case <-time.After(100 * time.Millisecond):
    74  		case <-timeout:
    75  			return h.readyFunc()
    76  		}
    77  	}
    78  	return true
    79  }