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Using HashiCorp Consul with Kong Ingress Controller for Kubernetes

Configure Kong Ingress Controller for Kubernetes with transparent proxy on HashiCorp Consul service mesh to manage traffic to and between your Kubernetes services.

Jul 27 2021Rosemary Wang

Kubernetes ingress allows you to define and route traffic to services within a cluster — what is traditionally known as north-south traffic management. By combining a Kubernetes Ingress Controller with a service mesh, you can not only manage traffic to services but also between services in the cluster (called east-west traffic management). Ingress and service mesh resources can more effectively define and secure service-to-service communication.

In this post, you’ll learn how to use the Kong Ingress Controller for Kubernetes with the new transparent proxy feature in Consul service mesh. Our example deploys a Consul cluster and Kong Ingress Controller to a Kubernetes cluster on Google Kubernetes Engine. You can use any Kubernetes cluster as long as it supports the service type for LoadBalancer. The example uses a load balancer to expose the Consul UI and Kong proxy for external access. You will also need a Consul version (greater than 1.10) that supports transparent proxy.

After deploying Kong ingress and a Consul cluster, you will define and control traffic to Kong Gateway, a ui service, and a web service using Consul intentions. Once you have properly configured this, you can use Kong’s rate-limiting plugin to limit the requests to the ui service and manage north-south traffic. In order to control internal traffic between ui and web, you can use Consul’s service splitter to manage east-west traffic as you split traffic between two versions of the web service.

Architecture diagram of Kong ingress rate-limiting inbound requests to `ui` and Consul service mesh splitting traffic between two versions of web in a Kubernetes cluster.

»Deploy Consul to Kubernetes

To get started, you must deploy Consul to Kubernetes before creating the Kong Ingress Controller. This is because in order to add Kong ingress to a Consul service mesh, your Kubernetes cluster needs the Consul webhook to inject its sidecar proxies.

First, let’s add the HashiCorp Helm repository:

$ helm repo add hashicorp https://helm.releases.hashicorp.com

Update the Consul Helm chart:

$ helm repo update

Next, we need to define the Consul values for the Helm chart. The values should configure one Consul server, enable access control lists (ACLs), enable Consul transparent proxy (by default), start the Consul controller, and set up the Consul UI with a load balancer:

$ cat <<EOF > consul.yamlglobal: name: consul datacenter: kubernetes acls:   manageSystemACLs: true server: replicas: 1 client: enabled: true connectInject: enabled: true ui: enabled: true service:   type: LoadBalancer controller: enabled: trueEOF

Then, we install Consul using its Helm chart to the default namespace. The command will use the chart version v0.34.1:

$ helm install consul hashicorp/consul --version v0.34.1 --values consul.yaml

You should have pods for the Consul server, controller, injector for sidecar proxies, and Consul clients for each Kubernetes node:

$ kubectl get pods -l='app=consul' NAME                                                          READY   STATUS    RESTARTS   AGEconsul-2dk68                                                  1/1     Running   0          58sconsul-b2sv9                                                  1/1     Running   0          58sconsul-connect-injector-webhook-deployment-7864bb5f76-5kbdj   1/1     Running   0          58sconsul-connect-injector-webhook-deployment-7864bb5f76-psw9m   1/1     Running   0          58sconsul-controller-56657f6db6-lvxcg                            1/1     Running   0          58sconsul-server-0                                               1/1     Running   0          57sconsul-vzxn2                                                  1/1     Running   0          58sconsul-webhook-cert-manager-57bb5c668d-b8st6                  1/1     Running   0          58s

You can access the Consul UI at the IP address of the load balancer. Set the CONSUL_HTTP_ADDR environment variable to the load balancer’s IP address for additional debugging:

$ export CONSUL_HTTP_ADDR=$(kubectl get service consul-ui  -o jsonpath='{.status.loadBalancer.ingress[0].ip}')

The example enables system ACLs, which means you need a Consul token to log into the UI and access its API. You can retrieve the token in a Kubernetes secret and set it to CONSUL_HTTP_TOKEN in your terminal:

$ export CONSUL_HTTP_TOKEN=$(kubectl get secrets consul-bootstrap-acl-token -o jsonpath='{.data.token}' | base64 -d)

This example uses Consul’s application-aware intentions and traffic shaping. Set the protocol for proxy defaults to http to ensure you can configure Consul:

$ cat <<EOF | kubectl apply -f -apiVersion: consul.hashicorp.com/v1alpha1kind: ProxyDefaultsmetadata: name: globalspec: config:   protocol: httpEOF

»Deploy Kong Ingress Controller for Kubernetes

Now that we have set up Consul, we can deploy the Kong Ingress Controller. You can define values for the Kong for Kubernetes Helm chart to inject a Consul sidecar proxy. The Kong Helm chart includes many components, but you only need the ingress controller and the API gateway (called proxy in the chart).

Add the Kong Helm repository:

$ helm repo add kong https://charts.konghq.com

Update the Kong for Kubernetes Helm chart:

$ helm repo update

Be sure to set an environment variable with the name of your Helm release for Kong. You will need to set this before you deploy the chart because you have Consul ACLs enabled. Kong must have a service account name that matches its Helm release name in order to properly authenticate to Consul:

$ export KONG_RELEASE=external

Define the Kong values in a file called kong.yaml. Kong’s service account must match its service name, which the Kong chart defines as ${KONG_RELEASE}-kong-proxy. You want to register the kong-proxy service instead of the ingress controller to allow Consul to manage traffic between the ingress and its upstream UI service:

$ cat <<EOF > kong.yamlingressController: serviceAccount:   name: ${KONG_RELEASE}-kong-proxy podAnnotations: consul.hashicorp.com/connect-inject: "true" consul.hashicorp.com/transparent-proxy-exclude-inbound-ports: 8000,8443EOF

The Kong values include two pod annotations. The annotation for consul.hashicorp.com/connect-inject injects the Consul sidecar proxy. consul.hashicorp.com/transparent-proxy-exclude-inbound-ports allows access from the Kong load balancer to its API gateway. Transparent proxy enforces that any traffic in the cluster reaches only its intended destination. As a result, you must add an exception to Consul’s transparent proxy for traffic from load balancers to specific service ports.

Install Kong for Kubernetes to the default namespace. The command will use the chart version 2.3.0:

$ helm install ${KONG_RELEASE} kong/kong --version 2.3.0 --values kong.yaml

You can check on the Kong pod in Kubernetes. Its containers include the Kong Ingress Controller, Kong gateway proxy, and Consul proxy:

$ kubectl get pods -l='app.kubernetes.io/name=kong'  NAME                             READY   STATUS    RESTARTS   AGEexternal-kong-67cf5ffd69-9pt7r   3/3     Running   0          132m

When you check the Consul service catalog, you should have a service for external-kong-proxy and its sidecar, external-kong-proxy-sidecar-proxy. This means that you successfully injected a Consul sidecar proxy and added Kong’s API gateway to Consul service mesh:

$ consul catalog services consulexternal-kong-proxyexternal-kong-proxy-sidecar-proxy

Set the Consul service default for Kong to http, which will allow you to configure application-aware intentions for HTTP request management:

$ cat <<EOF | kubectl apply -f -apiVersion: consul.hashicorp.com/v1alpha1kind: ServiceDefaultsmetadata: name: ${KONG_RELEASE}-kong-proxyspec: protocol: httpEOF

»Deploy an Example Workload

With Consul and Kong running, you can now deploy two example services, ui and web, and configure routing between them.

Deploy the web service to the default namespace. It should include version 1 of the web service, deployment, service account, and Consul service defaults:

$ cat <<EOF | kubectl apply -f -apiVersion: consul.hashicorp.com/v1alpha1kind: ServiceDefaultsmetadata:  name: webspec:  protocol: http---apiVersion: v1kind: Servicemetadata:  name: web  labels:    app: webspec:  selector:    app: web  ports:    - name: http      protocol: TCP      port: 80      targetPort: 9090---apiVersion: v1kind: ServiceAccountmetadata:  name: web---apiVersion: apps/v1kind: Deploymentmetadata:  name: web  labels:    app: web    release: v1spec:  replicas: 1  selector:    matchLabels:      app: web      release: v1  template:    metadata:      annotations:        consul.hashicorp.com/connect-inject: "true"        consul.hashicorp.com/service-meta-version: v1      labels:        app: web        release: v1    spec:      serviceAccountName: web      containers:        - name: web          image: "nicholasjackson/fake-service:v0.19.1"          ports:            - containerPort: 9090          env:            - name: NAME              value: "Web (v1)"            - name: MESSAGE              value: "Web (v1)"          livenessProbe:            httpGet:              path: /health              port: 9090            initialDelaySeconds: 3            periodSeconds: 3EOF

Next, deploy the ui service to the default namespace. It should include the ui service, deployment, service account, and Consul service defaults. The ui service connects to the web service for backend processing. In the deployment, you define this as an environment variable labeled UPSTREAM_URIS and direct it to the web service.

The ingress.kubernetes.io/service-upstream: "true" annotation on the Kubernetes Service communicates to the Kong ingress controller that it needs to use the cluster IP address of the service instead of the pod IP addresses. Add the annotation and deploy the service:

$ cat <<EOF | kubectl apply -f -apiVersion: consul.hashicorp.com/v1alpha1kind: ServiceDefaultsmetadata:  name: uispec:  protocol: http---apiVersion: v1kind: Servicemetadata:  name: ui  labels:    app: ui  annotations:    ingress.kubernetes.io/service-upstream: "true"spec:  selector:    app: ui  ports:    - name: http      protocol: TCP      port: 80      targetPort: 9090---apiVersion: v1kind: ServiceAccountmetadata:  name: ui---apiVersion: apps/v1kind: Deploymentmetadata:  name: ui  labels:    app: uispec:  replicas: 1  selector:    matchLabels:      app: ui  template:    metadata:      annotations:        consul.hashicorp.com/connect-inject: "true"      labels:        app: ui    spec:      serviceAccountName: ui      containers:        - name: ui          image: "nicholasjackson/fake-service:v0.19.1"          ports:            - containerPort: 9090          env:            - name: NAME              value: "UI"            - name: MESSAGE              value: "UI"            - name: UPSTREAM_URIS              value: "http://web"          livenessProbe:            httpGet:              path: /health              port: 9090            initialDelaySeconds: 3            periodSeconds: 3EOF

The Consul cluster uses transparent proxy by default to resolve any Kubernetes DNS names to services. As a result, it will automatically resolve to the web service. However, transparent proxy enforces traffic between services in the cluster. You need to authorize communication between the ui and web services.

Create an app-aware intention in Kubernetes. The intention should allow any GET requests from ui service to / or /favicon.ico endpoints on the web service. When you create it, Consul propagates the configuration to proxies for ui and web services and allows communication between them:

$ cat <<EOF | kubectl apply -f -apiVersion: consul.hashicorp.com/v1alpha1kind: ServiceIntentionsmetadata:  name: ui-to-webspec:  destination:    name: web  sources:    - name: ui      permissions:        - action: allow          http:            pathExact: /            methods: ["GET"]        - action: allow          http:            pathExact: /favicon.ico            methods: ["GET"]EOF

You can verify this by forwarding the ui service to port 8080 on your machine:

$ kubectl port-forward svc/ui 8080:80

In a separate shell, make an API request to the UI service. It should return a JSON object that identifies a successful upstream_call to the web service:

$ curl localhost:8080/ {  "name": "UI",  "uri": "/",  "type": "HTTP",  "ip_addresses": [    "10.84.2.8"  ],  "start_time": "2021-07-14T20:41:45.417155",  "end_time": "2021-07-14T20:41:45.426953",  "duration": "9.797902ms",  "body": "UI",  "upstream_calls": {    "http://web": {      "name": "Web (v1)",      "uri": "http://web",      "type": "HTTP",      "ip_addresses": [        "10.84.1.17"      ],      "start_time": "2021-07-14T20:41:45.425330",      "end_time": "2021-07-14T20:41:45.425618",      "duration": "288.317µs",      "headers": {        "Content-Length": "254",        "Content-Type": "text/plain; charset=utf-8",        "Date": "Wed, 14 Jul 2021 20:41:45 GMT",        "Server": "envoy",        "X-Envoy-Upstream-Service-Time": "0"      },      "body": "Web (v1)",      "code": 200    }  },  "code": 200}

Return to your original terminal and close the connection to Kubernetes port forwarding.

»Rate Limit Requests to a Kubernetes Service

You want to allow anyone to access the ui service through Kong’s ingress. By directing all requests through Kong, you can audit and control the number of requests to the ui service. Kong’s rate-limiting plugin sets a limit to how many HTTP requests an upstream service can serve in a given amount of time.

Imagine the ui service can handle only 30 requests per minute. You can install the rate-limiting plugin to Kong and configure the policy to limit the number of requests:

$ cat <<EOF | kubectl apply -f -apiVersion: configuration.konghq.com/v1kind: KongPluginmetadata: name: rate-limitplugin: rate-limitingconfig: minute: 30 policy: localEOF

You need to define a Kubernetes Ingress resource with annotations for the Kong ingress class, the rate-limiting plugin, and to set konghq.com/preserve-host to false. Setting it to false discards the original header and enables the Consul proxy to forward the service correctly. The resource allows traffic to the ui service on port 80 but will apply the rate-limit if ui receives more than 30 requests per minute:

$ cat <<EOF | kubectl apply -f -apiVersion: networking.k8s.io/v1kind: Ingressmetadata:  name: ui  annotations:    kubernetes.io/ingress.class: kong    konghq.com/plugins: rate-limit    konghq.com/preserve-host: "false"spec:  rules:    - http:        paths:          - path: /            pathType: Prefix            backend:              service:                name: ui                port:                  number: 80EOF

You need to configure Consul to allow communication between the Kong gateway and the ui service. Create an intention that allows the proxy to direct external requests to the / and /ui endpoints:

$ cat <<EOF | kubectl apply -f -apiVersion: consul.hashicorp.com/v1alpha1kind: ServiceIntentionsmetadata: name: kong-to-uispec: destination:   name: ui sources:   - name: ${KONG_RELEASE}-kong-proxy     permissions:       - action: allow         http:           pathExact: /           methods: ['GET']       - action: allow         http:           pathPrefix: /ui           methods: ['GET']EOF

To verify that you rate-limited requests to the ui service, copy the Kong proxy IP address from Kubernetes. Open your browser and enter the Kong proxy’s IP address and go to the /ui path:

$ open http://$(kubectl get service ${KONG_RELEASE}-kong-proxy  -o jsonpath='{.status.loadBalancer.ingress[*].ip}')/ui

If you quickly refresh the browser a few times, you may receive an error from Kong’s proxy that you have hit the API rate limit.

GIF refreshing the browser repeatedly for the service and exceeding the rate limit in Kong.

»Shape Traffic between Kubernetes Services

Besides shaping inbound requests to services with Kong API gateway, you can use Consul to shape requests between services in a Kubernetes cluster. For example, you may need to update the web service from version 1 to version 2. However, you do not want to deploy version 2 and send all requests from ui to a new version without testing it! You want to increase traffic to the new version gradually.

Apply a new deployment for version 2 of the web service to the default namespace. Consul will register the new version as a new instance under the web service:

$ cat <<EOF | kubectl apply -f -apiVersion: apps/v1kind: Deploymentmetadata: name: web-v2 labels:   app: web   release: v2spec: replicas: 1 selector:   matchLabels:     app: web     release: v2 template:   metadata:     annotations:       consul.hashicorp.com/connect-inject: "true"       consul.hashicorp.com/service-meta-version: v2     labels:       app: web       release: v2   spec:     serviceAccountName: web     containers:       - name: web         image: "nicholasjackson/fake-service:v0.19.1"         ports:           - containerPort: 9090         env:           - name: NAME             value: "Web (v2)"           - name: MESSAGE             value: "Web (v2)"         livenessProbe:           httpGet:             path: /health             port: 9090           initialDelaySeconds: 3           periodSeconds: 3EOF

Create a Consul service resolver to define the service subsets for version 1 and version 2. It references the service metadata you set as part of the consul.hashicorp.com/service-meta-version: v2 annotation in the deployment:

$ cat <<EOF | kubectl apply -f -apiVersion: consul.hashicorp.com/v1alpha1kind: ServiceResolvermetadata: name: webspec: defaultSubset: v1 subsets:   v1:     filter: "Service.Meta.version == v1"   v2:     filter: "Service.Meta.version == v2"EOF

To start sending traffic to version 2 of the web service, create a Consul service splitter to send 50% of traffic to version 1 and 50% to version 2:

$ cat <<EOF | kubectl apply -f -apiVersion: consul.hashicorp.com/v1alpha1kind: ServiceSplittermetadata:  name: webspec:  splits:    - weight: 50      serviceSubset: v1    - weight: 50      serviceSubset: v2EOF

Consul will direct any requests from the ui service to each version of the web service. If you examine the routing for the web service in the Consul UI, you can verify the 50% traffic weight configured for the service splitter.

Consul UI routing for the web service indicates 50% of traffic going to version 2

To verify that you correctly configured Consul to split traffic between the two versions, copy the Kong proxy IP address from Kubernetes. Open your browser and enter the Kong proxy’s IP address with a path to /ui:

$ open http://$(kubectl get service ${KONG_RELEASE}-kong-proxy  -o jsonpath='{.status.loadBalancer.ingress[*].ip}')/ui

If you refresh the browser a few times, you’ll notice that some requests go to Web (v2) and others go to Web (v1) before your requests exceed Kong’s rate limit.

GIF refreshing the browser repeatedly and splitting traffic between version 1 and version 2 of web service.

»Conclusion

This post covered how to add Kong for Kubernetes to Consul’s service mesh, configure rate-limiting for external requests to a service, enforce network policies with intentions, and split traffic between two versions of a service. By using Consul with Kong’s Ingress Controller, you can control, secure, and shape north-south and east-west traffic for Kubernetes services.

For additional information on transparent proxy for Consul, review its documentation. You can learn more about managing traffic with Consul service mesh in our Learn tutorials.

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