318 lines
11 KiB
Plaintext
318 lines
11 KiB
Plaintext
---
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layout: docs
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page_title: Single Consul Datacenter in Multiple Kubernetes Clusters - Kubernetes
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description: Single Consul Datacenter deployed in multiple Kubernetes clusters
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---
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# Single Consul Datacenter in Multiple Kubernetes Clusters
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-> Requires consul-helm v0.32.1 or higher.
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This page describes how to deploy a single Consul datacenter in multiple Kubernetes clusters,
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with both servers and clients running in one cluster, and only clients running in the rest of the clusters.
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In this example, we will use two Kubernetes clusters, but this approach could be extended to using more than two.
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~> **Note:** This deployment topology requires that your Kubernetes clusters have a flat network
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for both pods and nodes, so that pods or nodes from one cluster can connect
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to pods or nodes in another.
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## Deploying Consul servers and clients in the first cluster
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First, we will deploy the Consul servers with Consul clients in the first cluster.
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For that, we will use the following Helm configuration:
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<CodeBlockConfig filename="cluster1-config.yaml">
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```yaml
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global:
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datacenter: dc1
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tls:
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enabled: true
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enableAutoEncrypt: true
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acls:
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manageSystemACLs: true
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gossipEncryption:
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secretName: consul-gossip-encryption-key
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secretKey: key
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connectInject:
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enabled: true
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controller:
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enabled: true
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ui:
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service:
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type: NodePort
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```
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</CodeBlockConfig>
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Note that we are deploying in a secure configuration, with gossip encryption,
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TLS for all components, and ACLs. We are enabling the Consul Service Mesh and the controller for CRDs
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so that we can use them to later verify that our services can connect with each other across clusters.
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We're also setting UI's service type to be `NodePort`.
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This is needed so that we can connect to servers from another cluster without using the pod IPs of the servers,
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which are likely going to change.
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To deploy, first we need to generate the Gossip encryption key and save it as a Kubernetes secret.
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```shell
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$ kubectl create secret generic consul-gossip-encryption-key --from-literal=key=$(consul keygen)
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```
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Now we can install our Consul cluster with Helm:
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```shell
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$ helm install cluster1 --values cluster1-config.yaml hashicorp/consul
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```
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~> **Note:** The Helm release name must be unique for each Kubernetes cluster.
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That is because the Helm chart will use the Helm release name as a prefix for the
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ACL resources that it creates, such as tokens and auth methods. If the names of the Helm releases
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are the same, the Helm installation in subsequent clusters will clobber existing ACL resources.
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Once the installation finishes and all components are running and ready,
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we need to extract the gossip encryption key we've created, the CA certificate
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and the ACL bootstrap token generated during installation,
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so that we can apply them to our second Kubernetes cluster.
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```shell-session
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$ kubectl get secret consul-gossip-encryption-key cluster1-consul-ca-cert cluster1-consul-bootstrap-acl-token --output yaml > cluster1-credentials.yaml
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```
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## Deploying Consul clients in the second cluster
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~> **Note:** If multiple Kubernetes clusters will be joined to the Consul Datacenter, then the following instructions will need to be repeated for each additional Kubernetes cluster.
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Now we can switch to the second Kubernetes cluster where we will deploy only the Consul clients
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that will join the first Consul cluster.
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First, we need to apply credentials we've extracted from the first cluster to the second cluster:
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```shell-session
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$ kubectl apply --filename cluster1-credentials.yaml
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```
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To deploy in the second cluster, we will use the following Helm configuration:
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<CodeBlockConfig filename="cluster2-config.yaml" highlight="6-11,15-17">
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```yaml
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global:
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enabled: false
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datacenter: dc1
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acls:
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manageSystemACLs: true
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bootstrapToken:
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secretName: cluster1-consul-bootstrap-acl-token
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secretKey: token
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gossipEncryption:
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secretName: consul-gossip-encryption-key
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secretKey: key
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tls:
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enabled: true
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enableAutoEncrypt: true
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caCert:
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secretName: cluster1-consul-ca-cert
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secretKey: tls.crt
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externalServers:
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enabled: true
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# This should be any node IP of the first k8s cluster
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hosts: ["10.0.0.4"]
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# The node port of the UI's NodePort service
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httpsPort: 31557
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tlsServerName: server.dc1.consul
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# The address of the kube API server of this Kubernetes cluster
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k8sAuthMethodHost: https://kubernetes.example.com:443
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client:
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enabled: true
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join: ["provider=k8s kubeconfig=/consul/userconfig/cluster1-kubeconfig/kubeconfig label_selector=\"app=consul,component=server\""]
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extraVolumes:
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- type: secret
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name: cluster1-kubeconfig
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load: false
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connectInject:
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enabled: true
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```
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</CodeBlockConfig>
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Note that we're referencing secrets from the first cluster in ACL, gossip, and TLS configuration.
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Next, we need to set up the `externalServers` configuration.
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The `externalServers.hosts` and `externalServers.httpsPort`
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refer to the IP and port of the UI's NodePort service deployed in the first cluster.
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Set the `externalServers.hosts` to any Node IP of the first cluster,
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which you can see by running `kubectl get nodes --output wide`.
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Set `externalServers.httpsPort` to the `nodePort` of the `cluster1-consul-ui` service.
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In our example, the port is `31557`.
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```shell
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$ kubectl get service cluster1-consul-ui --context cluster1
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NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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cluster1-consul-ui NodePort 10.0.240.80 <none> 443:31557/TCP 40h
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```
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We set the `externalServer.tlsServerName` to `server.dc1.consul`. This the DNS SAN
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(Subject Alternative Name) that is present in the Consul server's certificate.
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We need to set it because we're connecting to the Consul servers over the node IP,
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but that IP isn't present in the server's certificate.
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To make sure that the hostname verification succeeds during the TLS handshake, we need to set the TLS
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server name to a DNS name that *is* present in the certificate.
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Next, we need to set `externalServers.k8sAuthMethodHost` to the address of the second Kubernetes API server.
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This should be the address that is reachable from the first cluster, and so it cannot be the internal DNS
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available in each Kubernetes cluster. Consul needs it so that `consul login` with the Kubernetes auth method will work
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from the second cluster.
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More specifically, the Consul server will need to perform the verification of the Kubernetes service account
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whenever `consul login` is called, and to verify service accounts from the second cluster it needs to
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reach the Kubernetes API in that cluster.
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The easiest way to get it is to set it from your `kubeconfig` by running `kubectl config view` and grabbing
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the value of `cluster.server` for the second cluster.
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Lastly, we need to set up the clients so that they can discover the servers in the first cluster.
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For this, we will use Consul's cloud auto-join feature
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for the [Kubernetes provider](https://www.consul.io/docs/install/cloud-auto-join#kubernetes-k8s).
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To use it we need to provide a way for the Consul clients to reach the first Kubernetes cluster.
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To do that, we need to save the `kubeconfig` for the first cluster as a Kubernetes secret in the second cluster
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and reference it in the `clients.join` value. Note that we're making that secret available to the client pods
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by setting it in `client.extraVolumes`.
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~> **Note:** The kubeconfig you're providing to the client should have minimal permissions.
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The cloud auto-join provider will only need permission to read pods.
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Please see [Kubernetes Cloud auto-join](https://www.consul.io/docs/install/cloud-auto-join#kubernetes-k8s)
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for more details.
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Now we're ready to install!
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```shell-session
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$ helm install cluster2 --values cluster2-config.yaml hashicorp/consul
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```
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## Verifying the Consul Service Mesh works
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~> When Transparent proxy is enabled, services in one Kubernetes cluster that need to communicate with a service in another Kubernetes cluster must have a explicit upstream configured through the ["consul.hashicorp.com/connect-service-upstreams"](https://www.consul.io/docs/k8s/connect#consul-hashicorp-com-connect-service-upstreams) annotation.
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Now that we have our Consul cluster in multiple k8s clusters up and running, we will
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deploy two services and verify that they can connect to each other.
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First, we'll deploy `static-server` service in the first cluster:
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<CodeBlockConfig filename="static-server.yaml">
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```yaml
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---
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apiVersion: consul.hashicorp.com/v1alpha1
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kind: ServiceIntentions
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metadata:
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name: static-server
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spec:
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destination:
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name: static-server
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sources:
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- name: static-client
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action: allow
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---
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apiVersion: v1
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kind: Service
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metadata:
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name: static-server
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spec:
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type: ClusterIP
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selector:
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app: static-server
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ports:
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- protocol: TCP
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port: 80
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targetPort: 8080
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---
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apiVersion: v1
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kind: ServiceAccount
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metadata:
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name: static-server
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---
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: static-server
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: static-server
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template:
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metadata:
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name: static-server
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labels:
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app: static-server
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annotations:
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"consul.hashicorp.com/connect-inject": "true"
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spec:
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containers:
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- name: static-server
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image: hashicorp/http-echo:latest
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args:
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- -text="hello world"
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- -listen=:8080
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ports:
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- containerPort: 8080
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name: http
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serviceAccountName: static-server
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```
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</CodeBlockConfig>
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Note that we're defining a Service intention so that our services are allowed to talk to each other.
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Then we'll deploy `static-client` in the second cluster with the following configuration:
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<CodeBlockConfig filename="static-client.yaml">
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: static-client
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spec:
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selector:
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app: static-client
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ports:
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- port: 80
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---
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apiVersion: v1
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kind: ServiceAccount
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metadata:
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name: static-client
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---
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: static-client
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: static-client
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template:
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metadata:
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name: static-client
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labels:
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app: static-client
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annotations:
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"consul.hashicorp.com/connect-inject": "true"
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"consul.hashicorp.com/connect-service-upstreams": "static-server:1234"
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spec:
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containers:
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- name: static-client
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image: curlimages/curl:latest
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command: [ "/bin/sh", "-c", "--" ]
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args: [ "while true; do sleep 30; done;" ]
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serviceAccountName: static-client
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```
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</CodeBlockConfig>
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Once both services are up and running, we can connect to the `static-server` from `static-client`:
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```shell-session
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$ kubectl exec deploy/static-client -- curl --silent localhost:1234
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"hello world"
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```
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