GPA Webhook示例

简介

GPA(GeneralPodAutoscaler)提供了基于Webhook的机制来实现Workload的自动伸缩。例如：

apiVersion: autoscaling.ocgi.dev/v1alpha1
kind: GeneralPodAutoscaler
metadata:
  name: pa-squad
  namespace: default
spec:
  maxReplicas: 8
  minReplicas: 1
  scaleTargetRef:
    apiVersion: carrier.ocgi.dev/v1alpha1
    kind: Squad
    name: squad-example
  webhook:
    parameters:
      buffer: "2"
    service:
      name: gpa-webhook
      namespace: kube-system
      path: scale
      port: 8000

Webhook Server由用户自己实现，从而实现由用户来控制Workload的副本数量。

实现Webhook Server

这里 是一个针对Squad开发的Webhook Server示例。

Webhook Request and Response

Webhook api 定义如下


// AutoscaleRequest defines the request to webhook autoscaler endpoint
type AutoscaleRequest struct {
	// UID is used for tracing the request and response.
	UID types.UID `json:"uid"`
	// Name is the name of the workload(Squad, Statefulset...) being scaled
	Name string `json:"name"`
	// Namespace is the workload namespace
	Namespace string `json:"namespace"`
	// Parameters are the parameter that required by webhook
	Parameters map[string]string `json:"parameters"`
	// CurrentReplicas is the current replicas
	CurrentReplicas int32 `json:"currentReplicas"`
}

// AutoscaleResponse defines the response of webhook server
type AutoscaleResponse struct {
	// UID is used for tracing the request and response.
	// It should be same as it in the request.
	UID types.UID `json:"uid"`
	// Set to false if should not do scaling
	Scale bool `json:"scale"`
	// Replicas is targeted replica count from the webhookServer
	Replicas int32 `json:"replicas"`
}

// AutoscaleReview is passed to the webhook with a populated Request value,
// and then returned with a populated Response.
type AutoscaleReview struct {
	Request  *AutoscaleRequest  `json:"request"`
	Response *AutoscaleResponse `json:"response"`
}

  1. Webhook server接收到的信息包括workload name, namespace, parameters，currentReplicas

  2. Webhook 应该基于需要的扩缩容实际情况应该返回AutoscaleResponse结构，包含scale和 replicas, 如果scale设置为false， 代表当前不需要伸缩。

部署Webhook Server

在K8s中部署, 同时也支持不在K8s中部署

使用Webhook Mode是扩缩容

使用webhook 模式进行扩缩容, 需要在GPA中填写Webhook Server相关的信息， 如下所示：

如果webhook部署在K8s中, 我们可以添加Service相关的信息到service字段

    apiVersion: autoscaling.ocgi.dev/v1alpha1
    kind: GeneralPodAutoscaler
    metadata:
      name: pa-test1
    spec:
      maxReplicas: 8
      minReplicas: 2
      scaleTargetRef:
        apiVersion: carrier.ocgi.dev/v1alpha1
        kind: GameServerSet
        name: example
      webhook:
        service:
          namespace: kube-system
          name: demowebhook
          port: 8000
          path: scale
        parameters:
          buffer: "3"

如果webhook不是部署在K8s中, 我们需要填写service字段中的url

    apiVersion: autoscaling.ocgi.dev/v1alpha1
    kind: GeneralPodAutoscaler
    metadata:
      name: pa-test1
    spec:
      maxReplicas: 8
      minReplicas: 2
      scaleTargetRef:
        apiVersion: carrier.ocgi.dev/v1alpha1
        kind: GameServerSet
        name: example
      webhook:
        url: http://123.test.com:8080/scale
        parameters:
          buffer: "3"

Updated on 2020-11-24