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319 lines
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319 lines
12 KiB
Plaintext
---
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layout: docs
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page_title: Installing Consul on Kubernetes - Kubernetes
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sidebar_title: Get Started
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description: >-
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Consul can run directly on Kubernetes, both in server or client mode. For
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pure-Kubernetes workloads, this enables Consul to also exist purely within
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Kubernetes. For heterogeneous workloads, Consul agents can join a server
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running inside or outside of Kubernetes.
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---
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# Installing Consul on Kubernetes
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Consul can run directly on Kubernetes, both in server or client mode.
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For pure-Kubernetes workloads, this enables Consul to also exist purely
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within Kubernetes. For heterogeneous workloads, Consul agents can join
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a server running inside or outside of Kubernetes.
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This page starts with a large how-to section for various specific tasks.
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To learn more about the general architecture of Consul on Kubernetes, scroll
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down to the [architecture](/docs/k8s/installation#architecture) section.
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If you would like to get hands-on experience testing Consul as a service mesh
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for Kubernetes, check the guides in the [Getting Started with Consul service
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mesh](https://learn.hashicorp.com/consul/gs-consul-service-mesh/understand-consul-service-mesh?utm_source=WEBSITE&utm_medium=WEB_IO&utm_offer=ARTICLE_PAGE&utm_content=DOCS) track.
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## Helm Chart Installation
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The recommended way to run Consul on Kubernetes is via the
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[Helm chart](/docs/k8s/helm). This will install and configure
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all the necessary components to run Consul. The configuration enables you
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to run just a server cluster, just a client cluster, or both. Using the Helm
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chart, you can have a full Consul deployment up and running in minutes.
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A step-by-step beginner tutorial and accompanying video can be found at the
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[Minikube with Consul guide](https://learn.hashicorp.com/consul/getting-started-k8s/minikube?utm_source=consul.io&utm_medium=docs).
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While the Helm chart exposes dozens of useful configurations and automatically
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sets up complex resources, it **does not automatically operate Consul.**
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You are still responsible for learning how to monitor, backup,
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upgrade, etc. the Consul cluster.
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The Helm chart has no required configuration and will install a Consul
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cluster with sane defaults out of the box. Prior to going to production,
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it is highly recommended that you
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[learn about the configuration options](/docs/k8s/helm#configuration-values).
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~> **Security Warning:** By default, the chart will install an insecure configuration
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of Consul. This provides a less complicated out-of-box experience for new users,
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but is not appropriate for a production setup. It is highly recommended to use
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a properly secured Kubernetes cluster or make sure that you understand and enable
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the [recommended security features](/docs/internals/security). Currently,
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some of these features are not supported in the Helm chart and require additional
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manual configuration.
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### Prerequisites
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The Consul Helm chart works with Helm 2 and Helm 3. If using Helm 2, you will
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need to install Tiller by following the
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[Helm 2 Installation Guide](https://v2.helm.sh/docs/using_helm/#quickstart-guide).
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### Installing Consul
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Add the HashiCorp Helm Repository:
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```shell-session
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$ helm repo add hashicorp https://helm.releases.hashicorp.com
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"hashicorp" has been added to your repositories
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```
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Ensure you have access to the consul chart:
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```shell-session
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$ helm search repo hashicorp/consul
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NAME CHART VERSION APP VERSION DESCRIPTION
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hashicorp/consul 0.20.1 1.7.2 Official HashiCorp Consul Chart
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```
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Now you're ready to install Consul! To install Consul with the default
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configuration using Helm 3 run:
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```shell-session
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$ helm install consul hashicorp/consul --set global.name=consul
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NAME: consul
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...
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```
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-> If using Helm 2, run: `helm install --name consul hashicorp/consul --set global.name=consul`
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_That's it._ The Helm chart does everything to set up a recommended
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Consul-on-Kubernetes deployment.
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In a couple minutes, a Consul cluster will be formed and a leader
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elected and every node will have a running Consul agent.
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### Customizing Your Installation
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If you want to customize your installation,
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create a `config.yaml` file to override the default settings.
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You can learn what settings are available by running `helm inspect values hashicorp/consul`
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or by reading the [Helm Chart Reference](/docs/k8s/helm).
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For example, if you want to enable the [Consul Connect](/docs/k8s/connect) feature,
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use the following config file:
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```yaml
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# config.yaml
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global:
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name: consul
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connectInject:
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enabled: true
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```
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Once you've created your `config.yaml` file, run `helm install` with the `-f` flag:
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```shell-session
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$ helm install consul hashicorp/consul -f config.yaml
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NAME: consul
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...
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```
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If you've already installed Consul and want to make changes, you'll need to run
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`helm upgrade`. See [Upgrading](/docs/k8s/operations/upgrading) for more details.
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## Viewing the Consul UI
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The Consul UI is enabled by default when using the Helm chart.
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For security reasons, it isn't exposed via a `LoadBalancer` Service by default so you must
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use `kubectl port-forward` to visit the UI.
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#### TLS Disabled
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If running with TLS disabled, the Consul UI will be accessible via http on port 8500:
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```shell-session
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$ kubectl port-forward service/consul-server 8500:8500
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...
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```
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Once the port is forwarded navigate to [http://localhost:8500](http://localhost:8500).
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#### TLS Enabled
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If running with TLS enabled, the Consul UI will be accessible via https on port 8501:
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```shell-session
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$ kubectl port-forward service/consul-server 8501:8501
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...
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```
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Once the port is forwarded navigate to [https://localhost:8501](https://localhost:8501).
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~> You'll need to click through an SSL warning from your browser because the
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Consul certificate authority is self-signed and not in the browser's trust store.
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#### ACLs Enabled
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If ACLs are enabled, you will need to input an ACL token into the UI in order
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to see all resources and make modifications.
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To retrieve the bootstrap token that has full permissions, run:
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```shell-session
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$ kubectl get secrets/consul-bootstrap-acl-token --template={{.data.token}} | base64 -D
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e7924dd1-dc3f-f644-da54-81a73ba0a178%
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```
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Then paste the token into the UI under the ACLs tab (without the `%`).
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~> NOTE: If using multi-cluster federation, your kubectl context must be in the primary datacenter
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to retrieve the bootstrap token since secondary datacenters use a separate token
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with less permissions.
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### Exposing the UI via a service
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If you want to expose the UI via a Kubernetes Service, configure
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the [`ui.service` chart values](/docs/k8s/helm#v-ui-service).
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This service will allow requests to the Consul servers so it should
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not be open to the world.
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## Accessing the Consul HTTP API
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The Consul HTTP API should be accessed by communicating to the local agent
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running on the same node. While technically any listening agent (client or
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server) can respond to the HTTP API, communicating with the local agent
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has important caching behavior, and allows you to use the simpler
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[`/agent` endpoints for services and checks](/api/agent).
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For Consul installed via the Helm chart, a client agent is installed on
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each Kubernetes node. This is explained in the [architecture](/docs/k8s/installation#client-agents)
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section. To access the agent, you may use the
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[downward API](https://kubernetes.io/docs/tasks/inject-data-application/downward-api-volume-expose-pod-information/).
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An example pod specification is shown below. In addition to pods, anything
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with a pod template can also access the downward API and can therefore also
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access Consul: StatefulSets, Deployments, Jobs, etc.
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: consul-example
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spec:
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containers:
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- name: example
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image: 'consul:latest'
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env:
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- name: HOST_IP
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valueFrom:
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fieldRef:
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fieldPath: status.hostIP
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command:
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- '/bin/sh'
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- '-ec'
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- |
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export CONSUL_HTTP_ADDR="${HOST_IP}:8500"
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consul kv put hello world
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restartPolicy: Never
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```
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An example `Deployment` is also shown below to show how the host IP can
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be accessed from nested pod specifications:
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```yaml
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: consul-example-deployment
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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: consul-example
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template:
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metadata:
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labels:
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app: consul-example
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spec:
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containers:
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- name: example
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image: 'consul:latest'
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env:
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- name: HOST_IP
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valueFrom:
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fieldRef:
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fieldPath: status.hostIP
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command:
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- '/bin/sh'
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- '-ec'
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- |
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export CONSUL_HTTP_ADDR="${HOST_IP}:8500"
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consul kv put hello world
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```
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## Architecture
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We recommend running Consul on Kubernetes with the same
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[general architecture](/docs/internals/architecture)
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as running it anywhere else. There are some benefits Kubernetes can provide
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that eases operating a Consul cluster and we document those below. The standard
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[production deployment guide](https://learn.hashicorp.com/consul/datacenter-deploy/deployment-guide) is still an
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important read even if running Consul within Kubernetes.
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Each section below will outline the different components of running Consul
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on Kubernetes and an overview of the resources that are used within the
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Kubernetes cluster.
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### Server Agents
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The server agents are run as a **StatefulSet**, using persistent volume
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claims to store the server state. This also ensures that the
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[node ID](/docs/agent/options#_node_id) is persisted so that servers
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can be rescheduled onto new IP addresses without causing issues. The server agents
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are configured with
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[anti-affinity](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#affinity-and-anti-affinity)
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rules so that they are placed on different nodes. A readiness probe is
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configured that marks the pod as ready only when it has established a leader.
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A **Service** is registered to represent the servers and expose the various
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ports. The DNS address of this service is used to join the servers to each
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other without requiring any other access to the Kubernetes cluster. The
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service is configured to publish non-ready endpoints so that it can be used
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for joining during bootstrap and upgrades.
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Additionally, a **PodDisruptionBudget** is configured so the Consul server
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cluster maintains quorum during voluntary operational events. The maximum
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unavailable is `(n/2)-1` where `n` is the number of server agents.
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-> **Note:** Kubernetes and Helm do not delete Persistent Volumes or Persistent
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Volume Claims when a
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[StatefulSet is deleted](https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/#stable-storage),
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so this must done manually when removing servers.
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### Client Agents
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The client agents are run as a **DaemonSet**. This places one agent
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(within its own pod) on each Kubernetes node.
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The clients expose the Consul HTTP API via a static port (default 8500)
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bound to the host port. This enables all other pods on the node to connect
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to the node-local agent using the host IP that can be retrieved via the
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Kubernetes downward API. See
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[accessing the Consul HTTP API](/docs/k8s/installation#accessing-the-consul-http-api)
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for an example.
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There is a major limitation to this: there is no way to bind to a local-only
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host port. Therefore, any other node can connect to the agent. This should be
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considered for security. For a properly production-secured agent with TLS
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and ACLs, this is safe.
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Some people prefer to run **Consul agent per pod** architectures, since this
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makes it easy to register the pod as a service. However, this turns
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a pod into a "node" in Consul and also causes an explosion of resource usage
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since every pod needs a Consul agent. We recommend instead running an
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agent (in a dedicated pod) per node, via the DaemonSet. This maintains the
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node equivalence in Consul. Service registration should be handled via the
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catalog syncing feature with Services rather than pods.
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-> **Note:** Due to a limitation of anti-affinity rules with DaemonSets,
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a client-mode agent runs alongside server-mode agents in Kubernetes. This
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duplication wastes some resources, but otherwise functions perfectly fine.
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