KEDA - 一个基于事件驱动的伸缩控制器

keda是一个基于事件驱动的伸缩控制器，可以实现应用缩容至0，以及从0开始扩容。目前已支持像CPU/Memroy、Mysql、Prometheus、Redis等20多种事件来源(Scaler)。

目前也是CNCF下的sandbox项目，最初主要由微软、redhat以及社区的人员参与贡献。

网站：https://keda.sh/

项目地址：https://github.com/kedacore/keda

KEDA架构图：

安装

keda 2.0版本要求k8s集群>=1.16

支持多种安装方式，可以查看keda文档：https://keda.sh/docs/2.0/deploy/#install

比如直接使用YAML文件安装：

kubectl apply -f https://github.com/kedacore/keda/releases/download/v2.0.0/keda-2.0.0.yaml

检查集群中是否安装成功：

>kubectl get pod -n keda
NAME                                      READY   STATUS    RESTARTS   AGE
keda-metrics-apiserver-5bffbfbd68-s7pbn   1/1     Running   10         2d23h
keda-operator-7b98595dc7-tvgr9            1/1     Running   19         2d23h

基本使用

KEDA 2.0有两种控制对象：

• ScaledObject：基于HPA，根据事件触发器(scaler)控制应用(Deployments, StatefulSets & Custom Resources)的水平伸缩
• ScaledJob：根据事件触发器(scaler)，生成job

ScaledObject配置

apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: {scaled-object-name}
spec:
  scaleTargetRef:
    apiVersion:    {api-version-of-target-resource}  # Optional. Default: apps/v1
    kind:          {kind-of-target-resource}         # Optional. Default: Deployment
    name:          {name-of-target-resource}         # Mandatory. Must be in the same namespace as the ScaledObject
    envSourceContainerName: {container-name}         # Optional. Default: .spec.template.spec.containers[0]
  pollingInterval: 30                                # Optional. Default: 30 seconds
  cooldownPeriod:  300                               # Optional. Default: 300 seconds
  minReplicaCount: 0                                 # Optional. Default: 0
  maxReplicaCount: 100                               # Optional. Default: 100
  advanced:                                          # Optional. Section to specify advanced options
    restoreToOriginalReplicaCount: true/false        # Optional. Default: false
    horizontalPodAutoscalerConfig:                   # Optional. Section to specify HPA related options
      behavior:                                      # Optional. Use to modify HPA's scaling behavior
        scaleDown:
          stabilizationWindowSeconds: 300
          policies:
          - type: Percent
            value: 100
            periodSeconds: 15
  triggers:
  # {list of triggers to activate scaling of the target resource}

参数说明：

比如创建一个基于prometheus的数据作为触发器的scaledobject:

apiVersion: keda.k8s.io/v1alpha1
kind: ScaledObject
metadata:
  name: prometheus-scaledobject
  namespace: default
spec:
  scaleTargetRef:
    deploymentName: http-demo
  minReplicaCount: 1
  triggers:
  - type: prometheus
    metadata:
      serverAddress: http://192.168.99.100:31046/
      metricName: gin_requests_total
      threshold: '2'
      query: sum(rate(gin_requests_total{app="http-demo",code="200"}[2m]))

Scaling Jobs配置

apiVersion: keda.sh/v1alpha1
kind: ScaledJob
metadata:
  name: {scaled-job-name}
spec:
  jobTargetRef:
    parallelism: 1                            # [max number of desired pods](https://kubernetes.io/docs/concepts/workloads/controllers/jobs-run-to-completion/#controlling-parallelism)
    completions: 1                            # [desired number of successfully finished pods](https://kubernetes.io/docs/concepts/workloads/controllers/jobs-run-to-completion/#controlling-parallelism)
    activeDeadlineSeconds: 600                #  Specifies the duration in seconds relative to the startTime that the job may be active before the system tries to terminate it; value must be positive integer
    backoffLimit: 6                           # Specifies the number of retries before marking this job failed. Defaults to 6
    template:
      # describes the [job template](https://kubernetes.io/docs/concepts/workloads/controllers/jobs-run-to-completion/)
  pollingInterval: 30                         # Optional. Default: 30 seconds
  successfulJobsHistoryLimit: 5               # Optional. Default: 100. How many completed jobs should be kept.
  failedJobsHistoryLimit: 5                   # Optional. Default: 100. How many failed jobs should be kept.
  envSourceContainerName: {container-name}    # Optional. Default: .spec.JobTargetRef.template.spec.containers[0]
  maxReplicaCount: 100                        # Optional. Default: 100
  scalingStrategy:
    strategy: "custom"                        # Optional. Default: default. Which Scaling Strategy to use. 
    customScalingQueueLengthDeduction: 1      # Optional. A parameter to optimize custom ScalingStrategy.
    customScalingRunningJobPercentage: "0.5"  # Optional. A parameter to optimize custom ScalingStrategy.
  triggers:
  # {list of triggers to create jobs}

参数说明：

Scaler

支持的Scaler如下：

• ActiveMQ Artemis
• Apache Kafka
• AWS CloudWatch
• AWS Kinesis Stream
• AWS SQS Queue
• Azure Blob Storage
• Azure Event Hubs
• Azure Log Analytics
• Azure Monitor
• Azure Service Bus
• Azure Storage Queue
• CPU
• Cron
• External
• External Push
• Google Cloud Platform‎ Pub/Sub
• Huawei Cloudeye
• IBM MQ
• Liiklus Topic
• Memory
• Metrics API
• MySQL
• NATS Streaming
• PostgreSQL
• Prometheus
• RabbitMQ Queue
• Redis Lists
• Redis Streams