Use an Ingress controller to mirror network traffic - Container Service for Kubernetes

Container Service for Kubernetes (ACK) allows you to mirror network traffic across clusters. Traffic mirroring is used in system simulations and troubleshooting. This topic describes how to use an Ingress controller to mirror network traffic.

Prerequisites

Two ACK clusters are created. For more information, see Create an ACK managed cluster. In this topic, a cluster named K8s Product Cluster is used as the production environment and another cluster named K8s Stage Cluster is used as the staging environment.

Scenarios

Traffic mirroring can be used in the following scenarios:

Before you make significant changes to a system or release new features, you must run stress tests to evaluate the stability of the system. In most cases, production workloads are simulated in a staging environment to test the stability of a new system before the system is released. However, the actual loads are difficult to estimate because the system may receive both normal and abnormal network traffic. To resolve this issue, you can mirror network traffic from applications that are deployed in the production environment to the staging environment. Then, you can simulate the production workloads in the staging environment.
When a system deployed in the production environment encounters a performance bottleneck and you cannot locate the cause, you can mirror the network traffic of the system to a staging environment. This way, you can troubleshoot errors in the staging environment.

Step 1: Deploy basic applications

Deploy applications in the cluster named K8s Product Cluster and test access to the applications.

Deploy an application in the cluster named K8s Product Cluster and use an Ingress to expose the Services in the cluster.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      # A previous version of the image is deployed. 
      - image: registry.cn-hangzhou.aliyuncs.com/acs-sample/old-nginx
        imagePullPolicy: Always
        name: nginx
        ports:
        - containerPort: 80
          protocol: TCP
      restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: nginx
  type: NodePort
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: nginx-ingress
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /
        backend:
          service: 
            name: nginx-service
            port:
              number: 80
        pathType: ImplementationSpecific

Run the following command to view the Ingress configurations:

kubectl get ing nginx-ingress

Expected output:

NAME            HOSTS         ADDRESS         PORTS     AGE
nginx-ingress   example.com   47.110.1**.**   80        8m

Run the following command to check whether you can access the domain name of the application:
```
curl http://example.com
```

Deploy the same application in the cluster named K8s Stage Cluster and test access to the application.

Deploy the same application in the cluster named K8s Stage Cluster and use an Ingress to expose the Services in the cluster.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      # The latest version of the image is deployed. 
      - image: registry.cn-hangzhou.aliyuncs.com/acs-sample/new-nginx
        imagePullPolicy: Always
        name: nginx
        ports:
        - containerPort: 80
          protocol: TCP
      restartPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: nginx
  type: NodePort
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: nginx-ingress
spec:
  rules:
  - host: example1.com
    http:
      paths:
      - path: /
        backend:
          service: 
            name: nginx-service
            port:
              number: 80
        pathType: ImplementationSpecific

Run the following command to view the Ingress configurations:

kubectl get ing nginx-ingress

Expected output:

NAME            HOSTS          ADDRESS        PORTS     AGE
nginx-ingress   example1.com   39.106.***.*   80        1m

Run the following command to check whether you can access the domain name of the application:
```
curl http://example1.com
```

Step 2: Mirror the network traffic

Mirror all network traffic of the application deployed in the cluster K8s Product Cluster to Services in the cluster K8s Stage Cluster. This way, all requests that are sent to the domain name example.com are replicated to the domain name example1.com.

Note

The Ingress of the cluster K8s Stage Cluster functions only as a receiver of the mirrored network traffic. Do not modify the configurations of the Ingress in the cluster K8s Stage Cluster. You can modify the Ingress of the cluster K8s Product Cluster.
After the network traffic of the application deployed in the cluster K8s Product Cluster is mirrored to Services in the cluster K8s Stage Cluster, the client receives responses only from the cluster K8s Product Cluster. Responses from the cluster K8s Stage Cluster are dropped.

Run the following command to modify nginx-configuration. Set the percentage of network traffic that you want to mirror and specify the domain name that receives the mirrored network traffic:

kubectl -n kube-system edit cm nginx-configuration

Add the following content to nginx-configuration:

http-snippet: |
   split_clients "$date_gmt" $mirror_servers {
      100%    example1.com;
   }

# Notes on configurations:
# 1. The percentage of network traffic that you want to mirror must be greater than 0 and can be up to 100. The sum of percentage cannot exceed 100. 
# 2. You can set one or more applications to receive the mirrored network traffic.

Run the following command to modify nginx-ingress:

You can add traffic mirroring settings to the source Ingress by setting the configuration-snippet and server-snippet annotations.

kubectl edit ingress nginx-ingress

Modify configuration-snippet and server-snippet of the nginx-ingress controller based on your business requirements. The following YAML file is an example:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: nginx-ingress
  annotations:
    nginx.ingress.kubernetes.io/configuration-snippet: |
        mirror /mirror; # You can repeat this setting N times to mirror the network traffic N times.
    nginx.ingress.kubernetes.io/server-snippet: |
        location = /mirror {
            internal;
            # Does not print the log of mirrored requests
            #access_log off; 
            # Set proxy_upstream_name in the following format: [Namespace]-[BackendServiceName]-[BackendServicePort]
            set $proxy_upstream_name    "default-nginx-service-80";
            # A custom string that is carried in the request header X-Shadow-Service and then passed to the mirror server.
            set $shadow_service_name    "nginx-product-service"; 
            proxy_set_header X-Shadow-Service  $shadow_service_name;
            proxy_set_header Host $mirror_servers;
            proxy_pass http://$mirror_servers$request_uri;
        }
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /
        backend:
          service: 
            name: nginx-service
            port:
              number: 80
        pathType: ImplementationSpecific

Verify the result

Access the domain name example.com. This domain name belongs to the application that is deployed in the cluster K8s Product Cluster. Run the following command. The output shows that each request sent to the domain name of the application deployed in the cluster K8s Product Cluster is replicated, and then sent to the application deployed in the cluster K8s Stage Cluster.

kubectl -n kube-system logs --tail=0 -f nginx-ingress-controller-674c96ffbc-9mc8n