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Source file src/k8s.io/kubernetes/pkg/scheduler/framework/plugins/examples/stateful/stateful.go

Documentation: k8s.io/kubernetes/pkg/scheduler/framework/plugins/examples/stateful

     1  /*
     2  Copyright 2019 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 stateful
    18  
    19  import (
    20  	"context"
    21  	"fmt"
    22  	"sync"
    23  
    24  	v1 "k8s.io/api/core/v1"
    25  	"k8s.io/apimachinery/pkg/runtime"
    26  	"k8s.io/klog/v2"
    27  	"k8s.io/kubernetes/pkg/scheduler/framework"
    28  )
    29  
    30  // MultipointExample is an example plugin that is executed at multiple extension points.
    31  // This plugin is stateful. It receives arguments at initialization (NewMultipointPlugin)
    32  // and changes its state when it is executed.
    33  type MultipointExample struct {
    34  	executionPoints []string
    35  	mu              sync.RWMutex
    36  }
    37  
    38  var _ framework.ReservePlugin = &MultipointExample{}
    39  var _ framework.PreBindPlugin = &MultipointExample{}
    40  
    41  // Name is the name of the plug used in Registry and configurations.
    42  const Name = "multipoint-plugin-example"
    43  
    44  // Name returns name of the plugin. It is used in logs, etc.
    45  func (mp *MultipointExample) Name() string {
    46  	return Name
    47  }
    48  
    49  // Reserve is the function invoked by the framework at "reserve" extension
    50  // point. In this trivial example, the Reserve method allocates an array of
    51  // strings.
    52  func (mp *MultipointExample) Reserve(ctx context.Context, state *framework.CycleState, pod *v1.Pod, nodeName string) *framework.Status {
    53  	// Reserve is not called concurrently, and so we don't need to lock.
    54  	mp.executionPoints = append(mp.executionPoints, "reserve")
    55  	return nil
    56  }
    57  
    58  // Unreserve is the function invoked by the framework when any error happens
    59  // during "reserve" extension point or later. In this example, the Unreserve
    60  // method loses its reference to the string slice, allowing it to be garbage
    61  // collected, and thereby "unallocating" the reserved resources.
    62  func (mp *MultipointExample) Unreserve(ctx context.Context, state *framework.CycleState, pod *v1.Pod, nodeName string) {
    63  	// Unlike Reserve, the Unreserve method may be called concurrently since
    64  	// there is no guarantee that there will only one unreserve operation at any
    65  	// given point in time (for example, during the binding cycle).
    66  	mp.mu.Lock()
    67  	defer mp.mu.Unlock()
    68  	mp.executionPoints = nil
    69  }
    70  
    71  // PreBind is the function invoked by the framework at "prebind" extension
    72  // point.
    73  func (mp *MultipointExample) PreBind(ctx context.Context, state *framework.CycleState, pod *v1.Pod, nodeName string) *framework.Status {
    74  	// PreBind could be called concurrently for different pods.
    75  	mp.mu.Lock()
    76  	defer mp.mu.Unlock()
    77  	mp.executionPoints = append(mp.executionPoints, "pre-bind")
    78  	if pod == nil {
    79  		return framework.NewStatus(framework.Error, "pod must not be nil")
    80  	}
    81  	return nil
    82  }
    83  
    84  // New initializes a new plugin and returns it.
    85  func New(ctx context.Context, config *runtime.Unknown, _ framework.Handle) (framework.Plugin, error) {
    86  	if config == nil {
    87  		klog.FromContext(ctx).Error(nil, "MultipointExample configuration cannot be empty")
    88  		return nil, fmt.Errorf("MultipointExample configuration cannot be empty")
    89  	}
    90  	mp := MultipointExample{}
    91  	return &mp, nil
    92  }
    93  

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