背景

需要在K8S集群中提供websocket服务。后端使用的是netty-socketio库实现了Socket.IO方式的ws服务。前端直接使用Socket.IO 客户端js实现。这里重点介绍AWS EKS中怎么通过启用ALB粘性会话的方式支持ws服务。

svc.yaml

apiVersion: v1
kind: Service
metadata:
  labels:
    app: {{ .Values.services.websocketServer.name }}
  name: {{ .Values.services.websocketServer.name }}
  namespace: {{ .Release.Namespace }}
  annotations:
    alb.ingress.kubernetes.io/target-group-attributes: stickiness.enabled=true,stickiness.lb_cookie.duration_seconds=60
    alb.ingress.kubernetes.io/healthcheck-path: {{ .Values.services.websocketServer.health.path }}
    alb.ingress.kubernetes.io/healthcheck-port: '{{ .Values.services.websocketServer.health.port }}'
    prometheus.io/path: {{ .Values.services.websocketServer.prometheus.path }}
    prometheus.io/port: '{{ .Values.services.websocketServer.prometheus.port }}'
    prometheus.io/scrape: "true"
spec:
  ports:
    - name: http
      port: {{ .Values.services.websocketServer.port }}
      targetPort: {{ .Values.services.websocketServer.port }}
  selector:
    app: {{ .Values.services.websocketServer.name }}
  type: ClusterIP

这里启用alb粘性会话关键就是如下一行：
alb.ingress.kubernetes.io/target-group-attributes: stickiness.enabled=true,stickiness.lb_cookie.duration_seconds=60

ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: {{ .Chart.Name }}-ingress
  namespace: {{ .Release.Namespace }}
  annotations:
    alb.ingress.kubernetes.io/load-balancer-name: {{ .Values.ingress.name }}
{{/*    alb.ingress.kubernetes.io/security-groups: {{ .Values.ingress.security.groups }}*/}}
    alb.ingress.kubernetes.io/manage-backend-security-group-rules: "true"
    alb.ingress.kubernetes.io/scheme: internet-facing
    alb.ingress.kubernetes.io/target-type: ip
    alb.ingress.kubernetes.io/listen-ports: '[{"HTTPS":443}]'
    alb.ingress.kubernetes.io/actions.response-503: >
      {"type":"fixed-response","fixedResponseConfig":{"contentType":"text/plain","statusCode":"503","messageBody":"503 error text"}}
spec:
  ingressClassName: alb
  tls:
    - hosts:
      - {{ .Values.ingress.tls.host }}
  rules:
  - http:
      paths:
      - path: /socket.io/
        backend:
          service:
            name: {{ .Values.services.websocketServer.name }}
            port:
              number: {{ .Values.services.websocketServer.port }}
        pathType: Prefix

这里启用alb粘性会话关键就是如下一行：

...
# 启用ip类型模式让alb查找目标组
    alb.ingress.kubernetes.io/target-type: ip
...
# 设置ingress拦截/socket.io/
      - path: /socket.io/
...

总结

aws eks 的ingress对应的alb支持ws服务还是很简单的，只要启用alb粘性会话就可以支持Socket.IO方式的ws服务了。netty-socketio代码可以参考netty-socketio-demo项目。
简单的socketio前端连接代码，如下：

var socket =  io('http://localhost:3000', {
	query: {
		"token": "xxxxx"
	},
	# 启用cookie
	withCredentials: true
});

这个socketio客户端连接代码，回向服务端发送一个GET请求，类似如下：

http://localhost:3000/socket.io/?token=xxxxxx&EIO=4&transport=polling&t=OzO3sO5

通过这个GET请求获取到一个set-cookie：io=146b8d76-719d-417f-8a8c-bf3a6a0d741f，写完这个cookie之后
前端会把io当做sid，将通过101 Switching Protocols会话升级为ws协议。

参考

• Socket.IO
• How to use websocket in ALB using aws-alb-ingress-controller
• Ingress annotations
• Application Load Balancer 的粘性会话
• Enabling sticky-session
• withCredentials