338 lines
12 KiB
Plaintext
338 lines
12 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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~> **Note:** For running Consul across multiple Kubernetes, it is generally recommended to utilize [Admin Partitions](/docs/enterprise/admin-partitions) for production environments. This Consul Enterprise feature allows for the ability to accommodate for multiple tenants without concerns of resource collisions when administering a cluster at scale, and for the ability to run Consul on Kubernetes clusters across a non-flat network.
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This page describes deploying a single Consul datacenter in multiple Kubernetes clusters,
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with servers and clients running in one cluster and only clients in the rest of the clusters.
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This example uses two Kubernetes clusters, but this approach could be extended to using more than two.
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## Requirements
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* Consul-Helm version `v0.32.1` or higher
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* This deployment topology requires that the 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. In many hosted Kubernetes environments, this may have to be explicitly configured based on the hosting provider's network. Refer to the following documentation for instructions:
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* [Azure AKS CNI](https://docs.microsoft.com/en-us/azure/aks/concepts-network#azure-cni-advanced-networking)
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* [AWS EKS CNI](https://docs.aws.amazon.com/eks/latest/userguide/pod-networking.html)
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* [GKE VPC-native clusters](https://cloud.google.com/kubernetes-engine/docs/concepts/alias-ips).
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* Either the Helm release name for each Kubernetes cluster must be unique, or `global.name` for each Kubernetes cluster must be unique to prevent collisions of ACL resources with the same prefix.
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## Prepare Helm release name ahead of installs
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The Helm release name must be unique for each Kubernetes cluster.
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The Helm chart uses 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 are identical, or if `global.name` for each cluster is identical, subsequent Consul on Kubernetes clusters will overwrite existing ACL resources and cause the clusters to fail.
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Before proceeding with installation, prepare the Helm release names as environment variables for both the server and client install.
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```shell-session
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$ export HELM_RELEASE_SERVER=server
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$ export HELM_RELEASE_CLIENT=client
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...
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$ export HELM_RELEASE_CLIENT2=client2
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```
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## Deploying Consul servers and clients in the first cluster
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First, deploy the first cluster with Consul Servers and Clients with the example Helm configuration below.
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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 this will deploy a secure configuration with gossip encryption,
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TLS for all components and ACLs. In addition, this will enable the Consul Service Mesh and the controller for CRDs
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that can be used later to verify the connectivity of services across clusters.
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The UI's service type is set to be `NodePort`.
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This is needed to 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 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=$(consul keygen)
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```
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Now install Consul cluster with Helm:
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```shell-session
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$ helm install ${HELM_RELEASE_SERVER} --values cluster1-config.yaml hashicorp/consul
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```
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Once the installation finishes and all components are running and ready, the following information needs to be extracted (using the below command) and applied to the second Kubernetes cluster.
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* The Gossip encryption key created
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* The CA certificate generated during installation
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* The ACL bootstrap token generated during installation
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```shell-session
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$ kubectl get secret consul-gossip-encryption-key ${HELM_RELEASE_SERVER}-consul-ca-cert ${HELM_RELEASE_SERVER}-consul-bootstrap-acl-token --output yaml > cluster1-credentials.yaml
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```
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## Deploying Consul clients in the second cluster
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~> **Note:** If multiple Kubernetes clusters will be joined to the Consul Datacenter, then the following instructions will need to be repeated for each additional Kubernetes cluster.
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Switch to the second Kubernetes cluster where Consul clients will be deployed
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that will join the first Consul cluster.
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```shell-session
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$ kubectl config use-context <K8S_CONTEXT_NAME>
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```
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First, apply the credentials 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, the following example Helm configuration will be used:
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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 the references to the secrets extracted and applied from the first cluster in ACL, gossip, and TLS 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 can be seen 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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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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This is required because the connection to the Consul servers uses 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, set the TLS
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server name to a DNS name that *is* present in the certificate.
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Next, 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, 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 from the `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, set up the clients so that they can discover the servers in the first cluster.
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For this, Consul's cloud auto-join feature
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for the [Kubernetes provider](/docs/install/cloud-auto-join#kubernetes-k8s) can be used.
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This can be configured by saving the `kubeconfig` for the first cluster as a Kubernetes secret in the second cluster
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and referencing it in the `clients.join` value. Note that the secret is made available to the client pods
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by setting it in `client.extraVolumes`.
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~> **Note:** The kubeconfig provided 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](/docs/install/cloud-auto-join#kubernetes-k8s)
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for more details.
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Now, proceed with the installation of the second cluster.
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```shell-session
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$ helm install ${HELM_RELEASE_CLIENT} --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 an explicit upstream configured through the ["consul.hashicorp.com/connect-service-upstreams"](/docs/k8s/annotations-and-labels#consul-hashicorp-com-connect-service-upstreams) annotation.
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Now that the Consul cluster spanning across multiple k8s clusters is up and running, deploy two services in separate k8s clusters and verify that they can connect to each other.
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First, 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 defining a Service intention is required so that our services are allowed to talk to each other.
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Next, 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, try connecting 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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A successful installation would return `hello world` for the above curl command output.
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