Advanced configurations of ALB Ingresses in ACK serverless clusters - Container Service for Kubernetes

An Ingress is an API object that you can use to provide Layer 7 load balancing services to manage external access to Services in an ACK Serverless cluster. This topic describes how to use Application Load Balancer (ALB) Ingresses to forward requests to backend server groups based on domain names and URL paths, redirect HTTP requests to HTTPS, and implement canary releases.

Prerequisites
Forward requests based on domain names
Forward requests based on URL paths
Configure health checks
Redirect HTTP requests to HTTPS
Configure HTTP and gRPC
Configure regular expressions
Configure rewrite rules
Configure custom listener ports
Configure the priorities of forwarding rules
Use annotations to perform canary releases
Configure session persistence by using annotations
Specify a load balancing algorithm for backend server groups
Configure CORS
Configure persistent TCP connections
Configure QPS throttling
Backend slow start
Connection draining

Prerequisites

An ACK Serverless cluster is created. You must configure a NAT gateway for the virtual private cloud (VPC) where the cluster is created to allow the cluster to download container images from the Internet. For more information, see ACK Serverless quick start.
The kubectl client is connected to the ASK cluster. For more information, see Connect to an ACK cluster by using kubectl.
An AlbConfig is created. For more information, see Create an AlbConfig.

Forward requests based on domain names

Perform the following steps to create an Ingress with a domain name and an Ingress without a domain name, and then use the Ingresses to forward requests.

Create an Ingress with a domain name

Use the following template to create a Deployment, a Service, and an Ingress. Requests to the domain name of the Ingress are forwarded to the Service.

Clusters that run Kubernetes 1.19 or later

apiVersion: v1
kind: Service
metadata:
  name: demo-service
  namespace: default
spec:
  ports:
    - name: port1
      port: 80
      protocol: TCP
      targetPort: 8080
  selector:
    app: demo
  sessionAffinity: None
  type: NodePort
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: demo
  template:
    metadata:
      labels:
        app: demo
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/alb-sample/cafe:v1
          imagePullPolicy: IfNotPresent
          name: demo
          ports:
            - containerPort: 8080
              protocol: TCP
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: demo
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - host: demo.domain.ingress.top
      http:
        paths:
          - backend:
              service:
                name: demo-service
                port: 
                  number: 80
            path: /hello
            pathType: ImplementationSpecific

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: v1
kind: Service
metadata:
  name: demo-service
  namespace: default
spec:
  ports:
    - name: port1
      port: 80
      protocol: TCP
      targetPort: 8080
  selector:
    app: demo
  sessionAffinity: None
  type: NodePort
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: demo
  template:
    metadata:
      labels:
        app: demo
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/alb-sample/cafe:v1
          imagePullPolicy: IfNotPresent
          name: demo
          ports:
            - containerPort: 8080
              protocol: TCP
---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: demo
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - host: demo.domain.ingress.top
      http:
        paths:
          - backend:
              serviceName: demo-service
              servicePort: 80
            path: /hello
            pathType: ImplementationSpecific

Run the following command to access the application by using the specified domain name.
Replace ADDRESS with the IP address of the related ALB instance. You can query the IP address by running the kubectl get ing command.
```
curl -H "host: demo.domain.ingress.top" <ADDRESS>/hello
```
Expected output:
```
{"hello":"coffee"}
```

Create an Ingress without a domain name

The following template shows the configuration of the Ingress:

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: demo
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - host: ""
      http:
        paths:
          - backend:
              service:
                name: demo-service
                port: 
                  number: 80
            path: /hello

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: demo
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - host: ""
      http:
        paths:
          - backend:
              serviceName: demo-service
              servicePort: 80
            path: /hello
            pathType: ImplementationSpecific

Run the following command to access the application without using a domain name.
Replace ADDRESS with the IP address of the related ALB instance. You can query the IP address by running the kubectl get ing command.
```
curl <ADDRESS>/hello
```
Expected output:
```
{"hello":"coffee"}
```

Forward requests based on URL paths

ALB Ingresses can forward requests based on URL paths. You can use the pathType parameter to configure different URL match policies. The valid values of pathType are Exact, ImplementationSpecific, and Prefix.

Note

URL match policies may conflict with each other. When conflicting URL match policies exist, requests are matched against the policies in descending order of policy priorities. For more information, see Configure forwarding rule priorities.

Match mode	Rule	URL path	Whether the URL path matches the rule
Prefix	/	(All paths)	Yes
Prefix	/foo	/foo /foo/	Yes
Prefix	/foo/	/foo /foo/	Yes
Prefix	/aaa/bb	/aaa/bbb	No
Prefix	/aaa/bbb	/aaa/bbb	Yes
Prefix	/aaa/bbb/	/aaa/bbb	Yes. The URL path ignores the trailing forward slash (/) of the rule.
Prefix	/aaa/bbb	/aaa/bbb/	Yes. The rule matches the trailing forward slash (/) of the URL path.
Prefix	/aaa/bbb	/aaa/bbb/ccc	Yes. The rule matches the subpath of the URL path.
Prefix	Configure two rules at the same time: / /aaa	/aaa/ccc	Yes. The URL path matches the `/` rule.
Prefix	Configure two rules at the same time: /aaa /	/aaa/ccc	Yes. The URL path matches the `/aaa` rule.
Prefix	Configure two rules at the same time: /aaa /	/ccc	Yes. The URL path matches the `/` rule.
Prefix	/aaa	/ccc	No
Exact or ImplementationSpecific	/foo	/foo	Yes
Exact or ImplementationSpecific	/foo	/bar	No
Exact or ImplementationSpecific	/foo	/foo/	No
Exact or ImplementationSpecific	/foo/	/foo	No

You can perform the following steps to configure different URL match policies.

Exact

The following template shows the configuration of the Ingress:

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: demo-path
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
        - path: /hello
          backend:
            service:
              name: demo-service
              port: 
                number: 80
          pathType: Exact

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: demo-path
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
        - path: /hello
          backend:
            serviceName: demo-service
            servicePort: 80
          pathType: Exact

Run the following command to access the application.
Replace ADDRESS with the IP address of the related ALB instance. You can query the IP address by running the kubectl get ing command.
```
curl <ADDRESS>/hello
```
Expected output:
```
{"hello":"coffee"}
```

ImplementationSpecific: the default match policy

The ALB Ingress configuration is the same as that for the Exact match policy.

The following template shows the configuration of the Ingress:

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: demo-path
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
        - path: /hello
          backend:
            service:
              name: demo-service
              port:
                number: 80
          pathType: ImplementationSpecific

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: demo-path
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
        - path: /hello
          backend:
            serviceName: demo-service
            servicePort: 80
          pathType: ImplementationSpecific

Run the following command to access the application.
Replace ADDRESS with the IP address of the related ALB instance. You can query the IP address by running the kubectl get ing command.

curl <ADDRESS>/hello

Expected output:

{"hello":"coffee"}

Prefix

Match a specified prefix against URL paths. The elements in URL paths are separated by forward slashes (/). The prefix is case-sensitive and matched against each element of the path.

The following template shows the configuration of the Ingress:

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: demo-path-prefix
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
        - path: /
          backend:
            service:
              name: demo-service
              port:
                number: 80
          pathType: Prefix

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: demo-path-prefix
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
        - path: /
          backend:
            serviceName: demo-service
            servicePort: 80
          pathType: Prefix

Run the following command to access the application.
Replace ADDRESS with the IP address of the related ALB instance. You can query the IP address by running the kubectl get ing command.

curl <ADDRESS>/hello

Expected output:

{"hello":"coffee"}

Configure health checks

You can configure health checks for ALB Ingresses by using the following annotations.

The following YAML template provides an example on how to create an Ingress for which health checks are enabled.

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: cafe-ingress
  annotations:
    alb.ingress.kubernetes.io/healthcheck-enabled: "true"
    alb.ingress.kubernetes.io/healthcheck-path: "/"
    alb.ingress.kubernetes.io/healthcheck-protocol: "HTTP"
    alb.ingress.kubernetes.io/healthcheck-httpversion: "HTTP1.1"
    alb.ingress.kubernetes.io/healthcheck-method: "HEAD"
    alb.ingress.kubernetes.io/healthcheck-code: "http_2xx"
    alb.ingress.kubernetes.io/healthcheck-timeout-seconds: "5"
    alb.ingress.kubernetes.io/healthcheck-interval-seconds: "2"
    alb.ingress.kubernetes.io/healthy-threshold-count: "3"
    alb.ingress.kubernetes.io/unhealthy-threshold-count: "3"
spec:
  ingressClassName: alb
  rules:
  - http:
      paths:
      # Configure a context path.
      - path: /tea
        backend:
          service:
            name: tea-svc
            port:
              number: 80
      # Configure a context path.
      - path: /coffee
        backend:
          service:
            name: coffee-svc
            port:
              number: 80

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: cafe-ingress
  annotations:
    alb.ingress.kubernetes.io/healthcheck-enabled: "true"
    alb.ingress.kubernetes.io/healthcheck-path: "/"
    alb.ingress.kubernetes.io/healthcheck-protocol: "HTTP"
    alb.ingress.kubernetes.io/healthcheck-method: "HEAD"
    alb.ingress.kubernetes.io/healthcheck-httpcode: "http_2xx"
    alb.ingress.kubernetes.io/healthcheck-timeout-seconds: "5"
    alb.ingress.kubernetes.io/healthcheck-interval-seconds: "2"
    alb.ingress.kubernetes.io/healthy-threshold-count: "3"
    alb.ingress.kubernetes.io/unhealthy-threshold-count: "3"
spec:
  ingressClassName: alb
  rules:
  - http:
      paths:
      # Configure a context path. 
      - path: /tea
        backend:
          serviceName: tea-svc
          servicePort: 80
      # Configure a context path. 
      - path: /coffee
        backend:
          serviceName: coffee-svc
          servicePort: 80

Parameter	Description
alb.ingress.kubernetes.io/healthcheck-enabled	Specifies whether to enable health checks for backend server groups. `true`: enables health checks. `false`: disables health checks. Default value: `false`.
alb.ingress.kubernetes.io/healthcheck-path	The URL path based on which health checks are performed. Default value: `/`.
alb.ingress.kubernetes.io/healthcheck-protocol	The protocol that is used for health checks. `HTTP`: performs HTTP health checks by sending HEAD or GET requests to a backend server to check whether the backend server is healthy. `HTTPS`: performs HTTPS health checks by sending HEAD or GET requests to a backend server to check whether the backend server is healthy. `TCP`: performs TCP health checks by sending SYN packets to the backend server to check whether the port of the backend server is available to receive requests. `GRPC`: performs gRPC health checks by sending POST or GET requests to a backend server to check whether the backend server is healthy. Default value: `HTTP`.
alb.ingress.kubernetes.io/healthcheck-httpversion	The version of the HTTP protocol. This parameter takes effect only when the `healthcheck-protocol` is set to `HTTP` or `HTTPS`. `HTTP1.0` `HTTP1.1` Default value: `HTTP1.1`.
alb.ingress.kubernetes.io/healthcheck-method	The request method that is used for health checks. `HEAD` `POST` `GET` Default value: `HEAD`. Important If you set `healthcheck-protocol` to `GRPC`, you must set this parameter to `POST` or `GET`.
alb.ingress.kubernetes.io/healthcheck-httpcode	The status codes returned for health checks. A backend server is considered healthy only when the health check request is successful and one of the specified status codes is returned. You can select one or more of the following status codes, and separate multiple status codes with commas (,): `http_2xx` `http_3xx` `http_4xx` `http_5xx` Default value: `http_2xx`.
alb.ingress.kubernetes.io/healthcheck-code	The status codes returned for health checks. A backend server is considered healthy only when the health check request is successful and one of the specified status codes is returned. If you specify both this parameter and `healthcheck-httpcode`, this parameter takes precedence. Values for this parameter depend on the value specified in `healthcheck-protocol`: `HTTP` or `HTTPS`: You can select one or more of the following status codes, and separate multiple status codes with commas (,): `http_2xx` `http_3xx` `http_4xx` `http_5xx` Default value: `http_2xx`. `GRPC`: Valid values: 0 to 99. Default value: `0`. Value ranges are supported. You can enter up to 20 value ranges and must separate each range with a comma (,).
alb.ingress.kubernetes.io/healthcheck-timeout-seconds	The timeout period of a health check. Unit: seconds. Valid values: 1 to 300. Default value: `5`.
alb.ingress.kubernetes.io/healthcheck-interval-seconds	The interval between two consecutive health checks. Unit: seconds. Valid values: 1 to 50. Default value: `2`.
alb.ingress.kubernetes.io/healthy-threshold-count	The number of times that a backend server must consecutively pass health checks before the server is considered healthy. Valid values: 2 to 10. Default value: `3`.
alb.ingress.kubernetes.io/unhealthy-threshold-count	The number of times that a backend server must consecutively fail health checks before the server is considered unhealthy. Valid values: 2 to 10. Default value: `3`.
alb.ingress.kubernetes.io/healthcheck-connect-port	The port that is used for health checks. Default value: `0`. Note A value of `0` indicates that the port on a backend server is used for health checks.

Redirect HTTP requests to HTTPS

You can configure an ALB Ingress to redirect HTTP requests to HTTPS port 443 by adding the alb.ingress.kubernetes.io/ssl-redirect: "true" annotation.

Important

You cannot create listeners by using an ALB Ingress. To ensure that an ALB Ingress can work as expected, you need to specify the ports and the protocols of listeners in an AlbConfig, and then associate the listeners with Services in the ALB Ingress.

Clusters that run Kubernetes versions earlier than V1.19

apiVersion: v1
kind: Service
metadata:
  name: demo-service-ssl
  namespace: default
spec:
  ports:
    - name: port1
      port: 80
      protocol: TCP
      targetPort: 8080
  selector:
    app: demo-ssl
  sessionAffinity: None
  type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo-ssl
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: demo-ssl
  template:
    metadata:
      labels:
        app: demo-ssl
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/alb-sample/cafe:v1
          imagePullPolicy: IfNotPresent
          name: demo-ssl
          ports:
            - containerPort: 8080
              protocol: TCP
---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/ssl-redirect: "true"
  name: demo-ssl
  namespace: default
spec:
  ingressClassName: alb
  tls:
  - hosts:
    - ssl.alb.ingress.top
  rules:
    - host: ssl.alb.ingress.top
      http:
        paths:
          - backend:
              serviceName: demo-service-ssl
              servicePort: 80
            path: /
            pathType: Prefix

Clusters that run Kubernetes V1.19 or later

apiVersion: v1
kind: Service
metadata:
  name: demo-service-ssl
  namespace: default
spec:
  ports:
    - name: port1
      port: 80
      protocol: TCP
      targetPort: 8080
  selector:
    app: demo-ssl
  sessionAffinity: None
  type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: demo-ssl
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: demo-ssl
  template:
    metadata:
      labels:
        app: demo-ssl
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/alb-sample/cafe:v1
          imagePullPolicy: IfNotPresent
          name: demo-ssl
          ports:
            - containerPort: 8080
              protocol: TCP
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/ssl-redirect: "true"
  name: demo-ssl
  namespace: default
spec:
  ingressClassName: alb
  tls:
  - hosts:
    - ssl.alb.ingress.top
  rules:
    - host: ssl.alb.ingress.top
      http:
        paths:
          - backend:
              service:
                name: demo-service-ssl
                port: 
                  number: 80
            path: /
            pathType: Prefix

Configure HTTPS or gRPC as the backend protocol

ALB Ingresses support HTTPS or gRPC as the backend protocol. To configure HTTPS or gRPC, add the alb.ingress.kubernetes.io/backend-protocol: "grpc" or alb.ingress.kubernetes.io/backend-protocol: "https" annotation. If you want to use an Ingress to distribute requests to a gRPC service, you must configure an SSL certificate for the gRPC service and use the TLS protocol to communicate with the gRPC service. Example:

Note

You cannot modify the backend protocol. If you need to change the protocol, delete and rebuild the Ingress.

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/backend-protocol: "grpc"
  name: lxd-grpc-ingress
spec:
  ingressClassName: alb
  tls:
  - hosts:
    - demo.alb.ingress.top
  rules:
  - host: demo.alb.ingress.top
    http:
      paths:  
      - path: /
        pathType: Prefix
        backend:
          service:
            name: grpc-demo-svc
            port:
              number: 9080

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/backend-protocol: "grpc"
  name: lxd-grpc-ingress
spec:
  ingressClassName: alb
  tls:
  - hosts:
    - demo.alb.ingress.top
  rules:
    - host: demo.alb.ingress.top
      http:
        paths:
          - backend:
              serviceName: grpc-demo-svc
              servicePort: 9080
            path: /
            pathType: Prefix

Configure regular expressions

You can specify regular expressions as routing conditions in the path field. Example:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
   alb.ingress.kubernetes.io/use-regex: "true" # Supports regular expressions in the path field. 
   alb.ingress.kubernetes.io/conditions.service-a: | # The Service specified in the annotation must be an existing Service in the cluster, and the Service name must be the same as the Service name in backend of the rule field. 
     [{
       "type": "Path",
       "pathConfig": {
           "values": [
              "~*^/pathvalue1", # The regular expression must follow the regular expression flag ~*.
              "/pathvalue2" # No need to add ~* before the path for exact match.
           ]
       }
      }]
  name: ingress-example
spec:
  ingressClassName: alb
  rules:
   - http:
      paths:
      - path: /test
        pathType: Prefix
        backend:
          service:
            name: service-a
            port:
              number: 88

Configure rewrite rules

ALB Ingresses support rewrite rules. To configure rewrite rules, add the annotation alb.ingress.kubernetes.io/rewrite-target: /path/${2}. The following rules apply:

In the rewrite-target annotation, you must set the pathType field to Prefix for variables of the ${number} type.
By default, the path parameter does not support characters that are supported by regular expressions, such as asterisks (*) and question marks (?). To specify characters that are used by regular expressions in the path parameter, you must add the rewrite-target annotation.
The value of the path parameter must start with a forward slash (/).

Note

If you want to specify regular expressions in rewrite rules, take note of the following items:

You can specify one or more regular expressions in the path field of an ALB Ingress and use parentheses () to enclose the regular expressions. However, you can use up to three variables (${1}, ${2}, and ${3}) in the rewrite-target annotation to form the path that overwrites the original path.
Variables that match the regular expressions are concatenated to form the path that overwrites the original path.
The original path is overwritten by the variables that match the regular expressions only if the following requirements are met: Multiple regular expressions that are enclosed in parentheses () are specified and the rewrite-target annotation is set to one or more of the following variables: ${1}, ${2}, and ${3}.

Assume that the path parameter of an ALB Ingress is set to /sys/(.*)/(.*)/aaa and the rewrite-target annotation is set to /${1}/${2}. If the client sends a request to the /sys/ccc/bbb/aaa path, the request matches the regular expression /sys/(.*)/(.*)/aaa. The rewrite-target annotation takes effect and replaces ${1} with ccc and ${2} with bbb. As a result, the request is redirected to /ccc/bbb.

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/use-regex: "true" # Supports regular expressions in the path field. 
    alb.ingress.kubernetes.io/rewrite-target: /path/${2} # Variables that match the regular expressions are concatenated to form the path that overwrites the original path. 
  name: rewrite-ingress
spec:
  ingressClassName: alb
  rules:
  - host: demo.alb.ingress.top
    http:
      paths:
      - path: /something(/|$)(.*)
        pathType: Prefix
        backend:
          service:
            name: rewrite-svc
            port:
              number: 9080

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/use-regex: "true" # Supports regular expressions in the path field. 
    alb.ingress.kubernetes.io/rewrite-target: /path/${2} # Variables that match the regular expressions are concatenated to form the path that overwrites the original path. 
  name: rewrite-ingress
spec:
  ingressClassName: alb
  rules:
    - host: demo.alb.ingress.top
      http:
        paths:
          - backend:
              serviceName: rewrite-svc
              servicePort: 9080
            path: /something(/|$)(.*)
            pathType: Prefix

Configure custom listening ports

ALB Ingresses allow you to configure custom listening ports. This allows you to expose a service through ports 80 and 443 at the same time.

Important

You cannot create listeners by using an ALB Ingress. To ensure that an ALB Ingress can work as expected, you need to specify the ports and protocols of listeners in an AlbConfig, and then associate the listeners with Services in the ALB Ingress.

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: cafe-ingress
  annotations:
   alb.ingress.kubernetes.io/listen-ports: '[{"HTTP": 80},{"HTTPS": 443}]'
spec:
  ingressClassName: alb
  tls:
  - hosts:
    - demo.alb.ingress.top
  rules:
  - host: demo.alb.ingress.top
    http:
      paths:
      - path: /tea
        pathType: ImplementationSpecific
        backend:
          service:
            name: tea-svc
            port:
              number: 80

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/listen-ports: '[{"HTTP": 80},{"HTTPS": 443}]'
  name: cafe-ingress
spec:
  ingressClassName: alb
  tls:
  - hosts:
    - demo.alb.ingress.top
  rules:
    - host: demo.alb.ingress.top
      http:
        paths:
          - backend:
              serviceName: tea-svc
              servicePort: 80
            path: /tea-svc
            pathType: ImplementationSpecific

Configure forwarding rule priorities

By default, forwarding rules are prioritized based on the following rules:

Forwarding rules of different ALB Ingresses are prioritized in the lexicographical order of the values of the namespace/name parameter. A forwarding rule whose namespace/name value appears the first among all forwarding rules in the lexicographical order has the highest priority.
The forwarding rules of an ALB Ingress are displayed in descending order of priority in the rule parameter.

If you do not want to use the namespace/name parameter of an ALB Ingress to prioritize forwarding rules, you can use the following annotation instead:

Note

The priority of each forwarding rule within a listener must be unique. You can use the annotation alb.ingress.kubernetes.io/order to specify the priorities of the forwarding rules of an ALB Ingress. Valid values: 1 to 1000. A smaller value indicates a higher priority. The default value is 10.

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: cafe-ingress
  annotations:
   alb.ingress.kubernetes.io/order: "2"
spec:
  ingressClassName: alb
  rules:
  - host: demo.alb.ingress.top
    http:
      paths:
      - path: /tea
        pathType: ImplementationSpecific
        backend:
          service:
            name: tea-svc
            port:
              number: 80

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/order: "2" 
  name: cafe-ingress
spec:
  ingressClassName: alb
  rules:
    - host: demo.alb.ingress.top
      http:
        paths:
          - backend:
              serviceName: tea-svc
              servicePort: 80
            path: /tea-svc
            pathType: ImplementationSpecific

Use annotations to perform phased releases

ALB allows you to configure canary releases based on request headers, cookies, and weights to handle complex traffic routing. You can add the annotation alb.ingress.kubernetes.io/canary: "true" to enable the canary release feature. Then, you can use the following annotations to configure different canary release rules.

Note

Canary releases that use different rules take effect in the following order: header-based > cookie-based > weight-based.
When you perform canary releases to test a new application version, do not modify the original Ingress rules. Otherwise, access to the application may be interrupted. After the new application version passes the test, replace the backend Service used by the earlier application version with the backend Service used by the new application version. Then, delete the Ingress rules for implementing canary releases.

alb.ingress.kubernetes.io/canary-by-header and alb.ingress.kubernetes.io/canary-by-header-value: This rule matches the headers and header values of requests. You must add both annotations if you want to use this rule.

If the header and header value of a request match the rule, the request is routed to the new application version.
If the header of a request does not match the header-based rule, the request is matched against other types of rules based on the priorities of the rules.

If you set the alb.ingress.kubernetes.io/canary-by-header annotation to location: hz, requests that match the rule are routed to the new application version. Requests that fail to match the rule are routed based on weight-based rules. Example:

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/order: "1"
    alb.ingress.kubernetes.io/canary: "true"
    alb.ingress.kubernetes.io/canary-by-header: "location"
    alb.ingress.kubernetes.io/canary-by-header-value: "hz"
  name: demo-canary
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
          - backend:
              service:
                name: demo-service-hello
                port: 
                  number: 80
            path: /hello
            pathType: ImplementationSpecific

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/order: "1"
    alb.ingress.kubernetes.io/canary: "true"
    alb.ingress.kubernetes.io/canary-by-header: "location"
    alb.ingress.kubernetes.io/canary-by-header-value: "hz"
  name: demo-canary
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
          - backend:
              serviceName:demo-service-hello
              servicePort: 80
            path: /hello
            pathType: ImplementationSpecific

alb.ingress.kubernetes.io/canary-by-cookie: This rule matches the cookies of requests.

If you set cookie to always, requests that match the rule are routed to the new application version.
If you set cookie to never, requests that match the rule are routed to the old application version.

Note

Cookie-based canary release rules do not support other settings. The cookie value must be always or never.

Requests that contain the demo=always cookie are routed to the new application version. Example:

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/order: "2"
    alb.ingress.kubernetes.io/canary: "true"
    alb.ingress.kubernetes.io/canary-by-cookie: "demo"
  name: demo-canary-cookie
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
          - backend:
              service:
                name: demo-service-hello
                port: 
                  number: 80
            path: /hello
            pathType: ImplementationSpecific

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/order: "2"
    alb.ingress.kubernetes.io/canary: "true"
    alb.ingress.kubernetes.io/canary-by-cookie: "demo"
  name: demo-canary-cookie
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
          - backend:
              serviceName:demo-service-hello
              servicePort: 80
            path: /hello
            pathType: ImplementationSpecific

alb.ingress.kubernetes.io/canary-weight: This rule allows you to set the percentage of requests that are sent to a specified Service. You can enter an integer from 0 to 100.

In the following example, the percentage of requests that are routed to the new application version is set to 50%:

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/order: "3"
    alb.ingress.kubernetes.io/canary: "true"
    alb.ingress.kubernetes.io/canary-weight: "50"
  name: demo-canary-weight
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
          - backend:
              service:
                name: demo-service-hello
                port: 
                  number: 80
            path: /hello
            pathType: ImplementationSpecific

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/order: "3"
    alb.ingress.kubernetes.io/canary: "true"
    alb.ingress.kubernetes.io/canary-weight: "50"
  name: demo-canary-weight
  namespace: default
spec:
  ingressClassName: alb
  rules:
    - http:
        paths:
          - backend:
              serviceName: demo-service-hello
              servicePort: 80
            path: /hello
            pathType: ImplementationSpecific

Configure session persistence by using annotations

ALB Ingresses allow you to configure session persistence by using the following annotations:

alb.ingress.kubernetes.io/sticky-session: specifies whether to enable session persistence. Valid values: true and false. Default value: false.
alb.ingress.kubernetes.io/sticky-session-type: the method that is used to handle a cookie. Valid values: Insert and Server. Default value: Insert.
- Insert: inserts a cookie. ALB inserts a cookie (SERVERID) into the first HTTP or HTTPS response packet that is sent to a client. The next request from the client contains this cookie and the listener distributes this request to the recorded backend server.
- Server: rewrites a cookie. When ALB detects a user-defined cookie, it overwrites the original cookie with the user-defined cookie. The next request from the client will contain the user-defined cookie, and the listener will distribute this request to the recorded backend server.
Note
This parameter takes effect when the StickySessionEnabled parameter is set to true for the server group.
alb.ingress.kubernetes.io/cookie-timeout: specifies the timeout period of cookies. Valid values: 1 to 86400. Default value: 1000. Unit: seconds.

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: cafe-ingress-v3
  annotations:
    alb.ingress.kubernetes.io/sticky-session: "true"
    alb.ingress.kubernetes.io/sticky-session-type: "Insert"
    alb.ingress.kubernetes.io/cookie-timeout: "1800"
spec:
  ingressClassName: alb
  rules:
  - http:
      paths:
      # Configure a context path. 
      - path: /tea2
        backend:
          service:
            name: tea-svc
            port: 
             number: 80
      # Configure a context path. 
       - path: /coffee2
         backend:
           service:
              name: coffee-svc
              port: 
               number: 80

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: cafe-ingress-v3
  annotations:
    alb.ingress.kubernetes.io/sticky-session: "true"
    alb.ingress.kubernetes.io/sticky-session-type: "Insert"
    alb.ingress.kubernetes.io/cookie-timeout: "1800"
spec:
  ingressClassName: alb
  rules:
  - http:
      paths:
      # Configure a context path. 
      - path: /tea2
        backend:
          serviceName: tea-svc
          servicePort: 80
      # Configure a context path. 
      - path: /coffee2
        backend:
          serviceName: coffee-svc
          servicePort: 80

Specify a load balancing algorithm for backend server groups

ALB Ingresses allow you to specify a load balancing algorithm for backend server groups by using the annotation alb.ingress.kubernetes.io/backend-scheduler. Example:

Clusters that run Kubernetes 1.19 or later

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: cafe-ingress
  annotations:
    alb.ingress.kubernetes.io/backend-scheduler: "uch" # Replace uch with wrr, sch, or wlc based on your business requirements. 
    alb.ingress.kubernetes.io/backend-scheduler-uch-value: "test" # This parameter is required only if the load balancing algorithm is uch. You do not need to configure this parameter if the scheduling algorithm is wrr, sch, or wlc. 
  name: cafe-ingress
spec:
  ingressClassName: alb
  rules:
  - host: demo.alb.ingress.top
    http:
      paths:
      - path: /tea
        pathType: ImplementationSpecific
        backend:
          service:
            name: tea-svc
            port:
              number: 80

Clusters that run Kubernetes versions earlier than 1.19

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/backend-scheduler: "uch" # Replace uch with wrr, sch, or wlc based on your business requirements. 
    alb.ingress.kubernetes.io/backend-scheduler-uch-value: "test" # This parameter is required only when the load balancing algorithm is uch. You do not need to configure this parameter when the scheduling algorithm is wrr, sch, or wlc. 
  name: cafe-ingress
spec:
  ingressClassName: alb
  rules:
    - host: demo.alb.ingress.top
      http:
        paths:
          - backend:
              serviceName: tea-svc
              servicePort: 80
            path: /tea-svc
            pathType: ImplementationSpecific

Set the annotation alb.ingress.kubernetes.io/backend-scheduler based on the following description:

wrr: Backend servers that have higher weights receive more requests than those that have lower weights. This is the default value.
wlc: Requests are distributed based on the weight and load of each backend server. The load refers to the number of connections to a backend server. If multiple backend servers have the same weight, requests are forwarded to the backend server with the least connections.
sch: consistent hashing that is based on source IP addresses.
uch: consistent hashing that is based on URL parameters. You can add the annotation alb.ingress.kubernetes.io/backend-scheduler-uch-value to the ALB Ingress to specify URL parameters for consistent hashing when the load balancing algorithm for backend server groups is uch.

Configure CORS

The following code block shows a sample Cross-origin Resource Sharing (CORS) configuration supported by ALB Ingresses:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: alb-ingress
  annotations:
    alb.ingress.kubernetes.io/enable-cors: "true"
    alb.ingress.kubernetes.io/cors-expose-headers: ""
    alb.ingress.kubernetes.io/cors-allow-methods: "GET,POST"
    alb.ingress.kubernetes.io/cors-allow-credentials: "true"
    alb.ingress.kubernetes.io/cors-max-age: "600"

spec:
  ingressClassName: alb
  rules:
  - host: demo.alb.ingress.top
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: cloud-nodeport
            port:
              number: 80

Parameter	Description
`alb.ingress.kubernetes.io/cors-allow-origin`	The URLs that can be used to access resources on the origin server by using a browser. Separate multiple URLs with commas (,). Each URL must start with http:// or https:// and contain a valid domain name or a top-level wildcard domain name. Default value: `*`. Example: `alb.ingress.kubernetes.io/cors-allow-origin: "https://example.com:4443, http://aliyundoc.com, https://example.org:1199"`.
`alb.ingress.kunbernetes.io/cors-allow`	The HTTP methods that are allowed. The values are not case-sensitive. Separate multiple HTTP methods with commas (,). Default value: `GET, PUT, POST, DELETE, PATCH, OPTIONS`. Example: `alb.ingress.kubernetes.io/cors-allow-methods: "PUT, GET, POST, OPTIONS"`.
`alb.ingress.kubernetes.io/cors-allow-headers`	The request headers that are allowed. The request headers can contain letters, digits, underscores (_), and hyphens (-). Separate multiple request headers with commas (,). Default value: `DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Authorization`. Example: `alb.ingress.kubernetes.io/cors-allow-headers: "X-Forwarded-For, X-app123-XPTO"`.
`alb.ingress.kubernetes.io/cors-expose-headers`	The headers that can be exposed. The headers can contain letters, digits, underscores (_), hyphens (-), and asterisks (). Separate multiple headers with commas (,). Default value: `empty`. Example: `alb.ingress.kubernetes.io/cors-expose-headers: ", X-CustomResponseHeader"`.
`alb.ingress.kubernetes.io/cors-allow-credentials`	Specifies whether to carry credentials in CORS requests. Default value: `true`. Example: `alb.ingress.kubernetes.io/cors-allow-credentials: "false"`.
`alb.ingress.kubernetes.io/cors-max-age`	The maximum period of time for which a preflight request that uses the OPTIONS method can be cached. Specify this parameter for complex requests. Valid values: -1 to 172800. Unit: seconds. Default value: `172800`.

Configure persistent TCP connections

Traditional load balancers access backend servers over short-lived connections. A traditional load balancer needs to create a connection and then close the connection each time the load balancer forwards a request to a backend server. Consequently, network connections become the performance bottleneck. To reduce the amount of resources that are used to establish network connections and improve the forwarding performance, you can use the persistent TCP connection feature. You can add the alb.ingress.kubernetes.io/backend-keepalive annotation to the ALB Ingress to enable the persistent TCP connection feature. Example:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: alb-ingress
  annotations:
    alb.ingress.kubernetes.io/backend-keepalive: "true"
spec:
  ingressClassName: alb
  rules:
  - host: demo.alb.ingress.top
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: cloud-nodeport
            port:
              number: 80

Configure QPS throttling

ALB supports QPS throttling based on forwarding rules. You can limit the QPS to a range of 1 to 100000. You can add the alb.ingress.kubernetes.io/traffic-limit-qps annotation to the ALB Ingress to enable the QPS throttling feature. Example:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: cafe-ingress
  annotations:
    alb.ingress.kubernetes.io/traffic-limit-qps: "50"
spec:
  ingressClassName: alb
  rules:
   - host: demo.alb.ingress.top
     http:
      paths:
      - path: /tea
        pathType: ImplementationSpecific
        backend:
          service:
            name: tea-svc
            port:
              number: 80
      - path: /coffee
        pathType: ImplementationSpecific
        backend:
          service:
            name: coffee-svc
            port:
              number: 80

Backend slow start

After a new pod is added to the Service backend, if the ALB Ingress immediately distributes traffic to the new pod, it may cause a sudden spike in CPU or memory usage, leading to access issues. In slow start mode, ALB Ingress gradually shifts traffic to the new pod to ease the impact of sudden traffic surges. The following sample code shows an example:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/slow-start-enabled: "true"
    alb.ingress.kubernetes.io/slow-start-duration: "100"
  name: alb-ingress
spec:
  ingressClassName: alb
  rules:
  - host: alb.ingress.alibaba.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: tea-svc
            port:
              number: 80

Parameter

Description

alb.ingress.kubernetes.io/slow-start-enabled

Specifies whether to enable the slow start mode.

true: enables slow start mode.
false: disables slow start mode.

By default, this mode is disabled.

alb.ingress.kubernetes.io/slow-start-duration

The time taken for the slow start to gradually increase traffic. The longer the duration, the slower the increase in traffic. Unit: seconds.

Valid values: 30 to 900.

Default value: 30.

Connection draining

If a pod enters the Terminating state, the ALB Ingress will remove it from the backend. However, ongoing requests may still exist in the established connections, and errors may occur if the ALB Ingress immediately closes all connections. With connection draining enabled, ALB Ingress keeps connections open for a specified period after the pod is removed, ensuring a smooth shutdown once current requests are completed. The connection draining modes are:

Disabled: When a pod enters the Terminating state, the ALB Ingress removes the pod from the backend and immediately closes all connections.
Enabled: When a pod enters the Terminating state, the ALB Ingress maintains ongoing requests open but does not accept new ones:
- If there are ongoing requests, the ALB Ingress closes all connections and removes the pod when the timeout is reached.
- If the pod completes all requests before the timeout, the ALB Ingress immediately removes it.

Important

Before the end of connection draining, ALB Ingress will not terminate its connections with the pod, but it cannot ensure the pod remains running. You can control the availability of the pod in the Terminating state by configuring spec.terminationGracePeriodSeconds or using a preStop hook.

The following sample code shows an example to configure connection draining:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/connection-drain-enabled: "true"
    alb.ingress.kubernetes.io/connection-drain-timeout: "199"
  name: alb-ingress
spec:
  ingressClassName: alb
  rules:
  - host: alb.ingress.alibaba.com
    http:
      paths:
      - path: /test
        pathType: Prefix
        backend:
          service:
            name: tea-svc
            port:
              number: 80

Parameter

Description

alb.ingress.kubernetes.io/connection-drain-enabled

Specifies whether to enable connection draining.

true: enables connection draining.
false: disables connection draining.

By default, connection draining is disabled.

alb.ingress.kubernetes.io/connection-drain-timeout

The timeout period of connection draining. Unit: seconds.

Valid values: 0 to 900.

Default value: 300.

Table of contents

Prerequisites

Forward requests based on domain names

Create an Ingress with a domain name

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Create an Ingress without a domain name

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Forward requests based on URL paths

Exact

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

ImplementationSpecific: the default match policy

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Prefix

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Configure health checks

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Redirect HTTP requests to HTTPS

Clusters that run Kubernetes versions earlier than V1.19

Clusters that run Kubernetes V1.19 or later

Configure HTTPS or gRPC as the backend protocol

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Configure regular expressions

Configure rewrite rules

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Configure custom listening ports

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Configure forwarding rule priorities

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Use annotations to perform phased releases

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Configure session persistence by using annotations

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Specify a load balancing algorithm for backend server groups

Clusters that run Kubernetes 1.19 or later

Clusters that run Kubernetes versions earlier than 1.19

Configure CORS

Configure persistent TCP connections

Configure QPS throttling

Backend slow start

Connection draining