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Connect an Elastic Kubernetes Service Cluster to HashiCorp Cloud Platform Consul

HashiCorp Cloud Platform (HCP) is a fully managed platform offering HashiCorp Products as a Service (HPaaS) to automate infrastructure on any cloud.

This tutorial will cover the process required to connect an EKS Cluster to HCP Consul on AWS.

»Prerequisites

The following prerequisites are required:

For this tutorial, you will need to ensure your AWS CLI is logged in with your credentials, and is targeting the region where you have created your EKS cluster. Review the AWS documentation for instructions on how to configure the AWS CLI.

To enable communication between the Consul control plane and the EKS cluster, you will need to complete the process outlined in the deployment tutorial.

»Configure development host

Kubernetes stores cluster connection information in a special file called kubeconfig. You can retrieve the Kubernetes configuration settings for your EKS cluster and merge them into your local kubeconfig file by issuing the following command. Note, you will have to change the region name and cluster name to match your environment.

$ aws eks --region <your-region> update-kubeconfig --name <your-cluster-name>

Now, download the Consul client configuration from the HCP portal by clicking the "Download client config" button from within the portal.

Unzip the client config package and cd into the unzipped directory. Confirm that there are both client_config.json and ca.pem files.

$ ls

ca.pem             client_config.json

From this same screen in the HCP UI, click the "Generate token" button and then click "Copy" from the dialog box. An global-management root token is now in your clipboard. Set it to the CONSUL_HTTP_TOKEN environment variable on your development host so that you can reference it later in the tutorial.

$ export CONSUL_HTTP_TOKEN=<your-token>

»Configure Consul secrets

Consul Service on HCP is secure by default. This means that client agents will need to be configured with the gossip encryption key, the Consul CA cert, and a root ACL token. All three of these secrets will need to be stored in the Kubernetes secrets engine so that they can be referenced and retrieved during the helm chart installation.

First, set an environment variable to the desired name of your Helm installation. This tutorial will use hcp-beta as the name.

$ export INSTALLATION_NAME=hcp-beta

From the unzipped client config directory, create a Kubernetes secret to store the Consul CA certificate:

$ kubectl create secret generic "${INSTALLATION_NAME}-consul-ca-cert" --from-file='tls.crt=./ca.pem'

Now, create a Kubernetes secret that stores the Consul Gossip key:

$ kubectl create secret generic "${INSTALLATION_NAME}-gossip-key" --from-literal="key=$(jq -r .encrypt client_config.json)"

Finally, create a Kubernetes secret to store the bootstrap ACL token you generated from the HCP UI:

$ kubectl create secret generic "${INSTALLATION_NAME}-bootstrap-token" --from-literal="token=${CONSUL_HTTP_TOKEN}"

»Install Consul clients on EKS

This tutorial will use the official consul-helm chart to install the Consul clients to your EKS cluster.

If you have not done so already, add the HashiCorp Helm repository:

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

Now, extract the private server URL from the client config so that it can be set in the Helm values file as the externalServers:hosts entry. This value will be passed as the retry-join option to the Consul clients.

$ export RETRY_JOIN=$(jq -r --compact-output .retry_join client_config.json)

Next, extract the public server URL from the client config so that it can be set the Helm values file as the k8sAuthMethodHost entry.

$ export CONSUL_HTTP_ADDR=$(kubectl config view -o jsonpath="{.clusters[?(@.name == \"$(kubectl config current-context)\")].cluster.server}")

Next, set CONSUL_HTTP_SSL_VERIFY=false so that you can interact with the HTTP API server using the Consul binary from your local development host.

export CONSUL_HTTP_SSL_VERIFY=false

Finally, generate the Helm values file. Notice that this configuration sets up an ingress gateway. This will be covered in more depth later.

$ cat > config.yaml << EOF
global:
  enabled: false
  datacenter: $(jq -r .datacenter client_config.json)
  acls:
    manageSystemACLs: true
    bootstrapToken:
      secretName: ${INSTALLATION_NAME}-bootstrap-token
      secretKey: token
  gossipEncryption:
    secretName: ${INSTALLATION_NAME}-gossip-key
    secretKey: key
  tls:
    enabled: true
    enableAutoEncrypt: true
    caCert:
      secretName: ${INSTALLATION_NAME}-consul-ca-cert
      secretKey: tls.crt
externalServers:
  enabled: true
  hosts: ${RETRY_JOIN}
  httpsPort: 443
  useSystemRoots: true
  k8sAuthMethodHost: ${CONSUL_HTTP_ADDR}
client:
  enabled: true
  join: ${RETRY_JOIN}
connectInject:
  enabled: true
ingressGateways:
  enabled: true
  defaults:
    replicas: 1
  gateways:
    - name: ingress-gateway
      service:
        type: LoadBalancer
EOF

Validate that the config file is populated correctly.

$ more config.yaml

Install the HashiCorp Consul Helm chart:

$ helm install "${INSTALLATION_NAME}" -f config.yaml hashicorp/consul

Once you have issued the helm install command, verify the Consul pods have been successfully deployed by issuing kubectl get pods.

$ kubectl get pods
NAME                                                      READY   STATUS    RESTARTS   AGE
hcp-beta-consul-6kdtq                                     1/1     Running   0          24s
hcp-beta-consul-connect-injector-webhook-deploymenfj8pv   1/1     Running   0          24s
hcp-beta-consul-ppc25                                     1/1     Running   0          24s
hcp-beta-consul-sjg89                                     1/1     Running   0          24s

»Deploy an example workload

Now that the clients have been deployed, it is time to deploy an application workload. This tutorial will use the HashiCups demo application. Issue the following command to clone the repository to the development host.

$ git clone https://github.com/hashicorp/learn-consul-k8s-hashicups.git

Change directory into the example repository.

cd learn-consul-k8s-hashicups

The repository contains the necessary yaml files to deploy the application. Issue the following command to deploy the application to your EKS cluster.

$ kubectl apply -f app/

Example output:

service/frontend created
serviceaccount/frontend created
configmap/nginx-configmap created
deployment.apps/frontend created
service/products-api-service created
serviceaccount/products-api created
configmap/db-configmap created
deployment.apps/products-api created
service/postgres created
serviceaccount/postgres created
deployment.apps/postgres created
service/public-api created
serviceaccount/public-api created
deployment.apps/public-api created

»Register a Consul ingress gateway

In Consul, an ingress gateway is a kind of resources called a Config Entry. An ingress gateway is an endpoint that allows external traffic to reach specific resources, such as the application user interface, that are hosted within the datacenter.

Create a file named ingress-gateway.hcl. You will use this to register an ingress gateway with Consul. Notice the Name value matches the ingressGateways:gateways:name entry in config.yaml. These fields must match.

$ cat > ingress-gateway.hcl << EOF
Kind = "ingress-gateway"
Name = "ingress-gateway"

Listeners = [
 {
   Port = 8080
   Protocol = "tcp"
   Services = [
     {
       Name = "frontend"
     }
   ]
 }
]
EOF

Now, register the config entry with Consul.

$ consul config write ingress-gateway.hcl

»Create the necessary intentions

Since HCP Consul on AWS is secure by default, the datacenter is created with a "default deny" intention in place. This means that, by default, no services can interact with each other until an operator explicitly allows them to do so by creating intentions for each inter-service operations they wish to allow.

Issue the following command to create the intentions the HashiCups application requires to run.

$ consul intention create ingress-gateway frontend && \
consul intention create frontend public-api && \
consul intention create public-api products-api && \
consul intention create products-api postgres

Example output:

Created: ingress-gateway => frontend (allow)
Created: frontend => public-api (allow)
Created: public-api => products-api (allow)
Created: products-api => postgres (allow)

»Access the HashiCups UI

With the intentions in place, all that remains is to retrieve the public URL and port of the ingress gateway. Do this by retrieving a list of services.

$ kubectl get svc

Example output:

NAME                          TYPE           CLUSTER-IP    EXTERNAL-IP      PORT(S)                         AGE
consul-ingress-gateway        ClusterIP      10.0.53.153   40.36.23.19      8080/TCP                        4h43m
...TRUNCATED

Verify you have successfully deployed the application by visiting that ip/port combination in a browser tab. This validates that Consul service discovery is working, because the services are able to resolve the upstreams. This also validates that Consul service mesh is working, because the intentions that were created are allowing services to interact with one another.

»Next steps

In this tutorial, you connected Consul clients on EKS to HCP Consul and deployed a demo application. To keep learning about Consul's features, and for step-by-step examples of how to perform common Consul tasks, complete one of the following tutorials.

If you encounter any issues, please contact the HCP team at support.hashicorp.com.

HashiCorp
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