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文档中心 > 容器服务 > 最佳实践 > 弹性伸缩 > 在 TKE 上使用自定义指标进行弹性伸缩

操作场景

容器服务 TKE 基于 Custom Metrics API 支持许多用于弹性伸缩的指标,涵盖 CPU、内存、硬盘、网络以及 GPU 相关的指标,覆盖绝大多数的 HPA 弹性伸缩场景,详细列表请参见 自动伸缩指标说明。针对例如基于业务单副本 QPS 大小来进行自动扩缩容等复杂场景,可通过安装 prometheus-adapter 来实现自动扩缩容。而 Kubernetes 提供 Custom Metrics API 与 External Metrics API 来对 HPA 指标进行扩展,让用户能够根据实际需求进行自定义。prometheus-adapter 支持以上两种 API,在实际环境中,使用 Custom Metrics API 即可满足大部分场景。本文将介绍如何通过 Custom Metrics API 实现使用自定义指标进行弹性伸缩。

前提条件

已创建1.12或以上版本的 TKE 集群,详情请参见 创建集群
已部署 Prometheus 并进行相应的自定义指标采集。
已安装 Helm

操作步骤

暴露监控指标

本文以 Golang 业务程序为例,该示例程序暴露了 httpserver_requests_total 指标,并记录 HTTP 的请求,通过该指标可以计算出业务程序的 QPS 值。示例如下:
package main

import (
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
"net/http"
"strconv"
)

var (
HTTPRequests = prometheus.NewCounterVec(
prometheus.CounterOpts{
Name: "httpserver_requests_total",
Help: "Number of the http requests received since the server started",
},
[]string{"status"},
)
)

func init() {
prometheus.MustRegister(HTTPRequests)
}

func main() {
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
path := r.URL.Path
code := 200
switch path {
case "/test":
w.WriteHeader(200)
w.Write([]byte("OK"))
case "/metrics":
promhttp.Handler().ServeHTTP(w, r)
default:
w.WriteHeader(404)
w.Write([]byte("Not Found"))
}
HTTPRequests.WithLabelValues(strconv.Itoa(code)).Inc()
})
http.ListenAndServe(":80", nil)
}

部署业务程序

将前面的程序打包成容器镜像,然后部署到集群,例如使用 Deployment 部署:
apiVersion: apps/v1
kind: Deployment
metadata:
name: httpserver
namespace: httpserver
spec:
replicas: 1
selector:
matchLabels:
app: httpserver
template:
metadata:
labels:
app: httpserver
spec:
containers:
- name: httpserver
image: registry.imroc.cc/test/httpserver:custom-metrics
imagePullPolicy: Always

---

apiVersion: v1
kind: Service
metadata:
name: httpserver
namespace: httpserver
labels:
app: httpserver
annotations:
prometheus.io/scrape: "true"
prometheus.io/path: "/metrics"
prometheus.io/port: "http"
spec:
type: ClusterIP
ports:
- port: 80
protocol: TCP
name: http
selector:
app: httpserver

Prometheus 采集业务监控

您可以通过 Prometheus 采集规则ServiceMonitor 配置 Prometheus 采集业务暴露的监控指标。

方式1:配置 Prometheus 采集规则

在 Prometheus 的采集规则配置文件中添加以下采集规则。示例如下:
scrape_configs:
- job_name: httpserver
scrape_interval: 10s
kubernetes_sd_configs:
- role: endpoints
namespaces:
names:
- httpserver
relabel_configs:
- action: keep
source_labels:
- __meta_kubernetes_service_label_app
regex: httpserver
- action: keep
source_labels:
- __meta_kubernetes_endpoint_port_name
regex: http

方式2:配置 ServiceMonitor

若已安装 prometheus-operator,可以通过创建 ServiceMonitor 的 CRD 对象配置 Prometheus。示例如下:
apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
name: httpserver
spec:
endpoints:
- port: http
interval: 5s
namespaceSelector:
matchNames:
- httpserver
selector:
matchLabels:
app: httpserver

安装 prometheus-adapter

1. 使用 Helm 安装 prometheus-adapter,安装前请确定并配置自定义指标。按照上文 暴露监控指标 中的示例,在业务中使用 httpserver_requests_total 指标来记录 HTTP 请求,因此可以通过如下的 PromQL 计算出每个业务 Pod 的 QPS 监控。示例如下:
sum(rate(http_requests_total[2m])) by (pod)
2. 将其转换为 prometheus-adapter 的配置,创建 values.yaml,内容如下:
rules:
default: false
custom:
- seriesQuery: 'httpserver_requests_total'
resources:
template: <<.Resource>>
name:
matches: "httpserver_requests_total"
as: "httpserver_requests_qps" # PromQL 计算出来的 QPS 指标
metricsQuery: sum(rate(<<.Series>>{<<.LabelMatchers>>}[1m])) by (<<.GroupBy>>)
prometheus:
url: http://prometheus.monitoring.svc.cluster.local # 替换 Prometheus API 的地址 (不写端口)
port: 9090
3. 执行以下 Helm 命令安装 prometheus-adapter,示例如下:
注意
安装前需要删除 TKE 已经注册的 Custom Metrics API,删除命令如下:
kubectl delete apiservice v1beta1.custom.metrics.k8s.io
helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo update
# Helm 3
helm install prometheus-adapter prometheus-community/prometheus-adapter -f values.yaml
# Helm 2
# helm install --name prometheus-adapter prometheus-community/prometheus-adapter -f values.yaml
4. 添加 prometheus 认证鉴权参数。
当前社区提供的 chart 中没有暴露认证鉴权相关的入参,会导致认证鉴权失败无法正常连接 TMP 服务,为了解决这个问题,您可以查看 社区文档。解决方案要求您手动修改 Prometheus Adapter deployment,在 adapter 启动参数中添加 --prometheus-header=Authorization=Basic {token},其中{token} 为您从控制台获取的 token。

测试验证

若安装正确,执行以下命令,可以查看到 Custom Metrics API 返回配置的 QPS 相关指标。示例如下:
$ kubectl get --raw /apis/custom.metrics.k8s.io/v1beta1
{
"kind": "APIResourceList",
"apiVersion": "v1",
"groupVersion": "custom.metrics.k8s.io/v1beta1",
"resources": [
{
"name": "jobs.batch/httpserver_requests_qps",
"singularName": "",
"namespaced": true,
"kind": "MetricValueList",
"verbs": [
"get"
]
},
{
"name": "pods/httpserver_requests_qps",
"singularName": "",
"namespaced": true,
"kind": "MetricValueList",
"verbs": [
"get"
]
},
{
"name": "namespaces/httpserver_requests_qps",
"singularName": "",
"namespaced": false,
"kind": "MetricValueList",
"verbs": [
"get"
]
}
]
}
执行以下命令,可以查看到 Pod 的 QPS 值。示例如下:
说明
下述示例 QPS 为500m,表示 QPS 值为0.5。
$ kubectl get --raw /apis/custom.metrics.k8s.io/v1beta1/namespaces/httpserver/pods/*/httpserver_requests_qps
{
"kind": "MetricValueList",
"apiVersion": "custom.metrics.k8s.io/v1beta1",
"metadata": {
"selfLink": "/apis/custom.metrics.k8s.io/v1beta1/namespaces/httpserver/pods/%2A/httpserver_requests_qps"
},
"items": [
{
"describedObject": {
"kind": "Pod",
"namespace": "httpserver",
"name": "httpserver-6f94475d45-7rln9",
"apiVersion": "/v1"
},
"metricName": "httpserver_requests_qps",
"timestamp": "2020-11-17T09:14:36Z",
"value": "500m",
"selector": null
}
]
}

测试 HPA

假如设置每个业务 Pod 的平均 QPS 达到50时将触发扩容,最小副本为1个,最大副本为1000个,则配置示例如下:
apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
metadata:
name: httpserver
namespace: httpserver
spec:
minReplicas: 1
maxReplicas: 1000
scaleTargetRef:
apiVersion: apps/v1
kind: Deployment
name: httpserver
metrics:
- type: Pods
pods:
metric:
name: httpserver_requests_qps
target:
averageValue: 50
type: AverageValue
执行以下命令对业务进行压测,观察是否自动扩容。示例如下:
$ kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
httpserver Deployment/httpserver 83933m/50 1 1000 2 18h
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
httpserver-6f94475d45-47d5w 1/1 Running 0 3m41s
httpserver-6f94475d45-7rln9 1/1 Running 0 37h
httpserver-6f94475d45-6c5xm 0/1 ContainerCreating 0 1s
httpserver-6f94475d45-wl78d 0/1 ContainerCreating 0 1s
若扩容正常,则说明已实现 HPA 基于业务自定义指标进行弹性伸缩。