--- layout: docs page_title: Service Mesh - Kubernetes description: >- Connect is a feature built into to Consul that enables automatic service-to-service authorization and connection encryption across your Consul services. Connect can be used with Kubernetes to secure pod communication with other services. --- # Connect Service Mesh on Kubernetes [Connect](/docs/connect) is a feature built into to Consul that enables automatic service-to-service authorization and connection encryption across your Consul services. Connect can be used with Kubernetes to secure pod communication with other pods and external Kubernetes services. The Connect sidecar running Envoy can be automatically injected into pods in your cluster, making configuration for Kubernetes automatic. This functionality is provided by the [consul-k8s project](https://github.com/hashicorp/consul-k8s) and can be automatically installed and configured using the [Consul Helm chart](/docs/k8s/installation/install). ## Usage When the [Connect injector is installed](/docs/k8s/connect#installation-and-configuration), the Connect sidecar can be automatically added to all pods. This sidecar can both accept and establish connections using Connect, enabling the pod to communicate to clients and dependencies exclusively over authorized and encrypted connections. -> **Note:** The examples in this section are valid and use publicly available images. If you've installed the Connect injector, feel free to run the examples in this section to try Connect with Kubernetes. Please note the documentation below this section on how to properly install and configure the Connect injector. ### Accepting Inbound Connections An example Deployment is shown below with Connect enabled to accept inbound connections. Notice that the Deployment would still be fully functional without Connect. Minimal to zero modifications are required to enable Connect in Kubernetes. Notice also that even though we're using a Deployment here, the same configuration would work on a Pod, a StatefulSet, or a DaemonSet. This Deployment specification starts a server that responds to any HTTP request with the static text "hello world". -> **Note:** As of consul-k8s `v0.26.0` and Consul Helm `v0.32.0`, having a Kubernetes service is **required** to run services on the Consul Service Mesh. ```yaml apiVersion: v1 kind: Service metadata: # This name will be the service name in Consul. name: static-server spec: selector: app: static-server ports: - protocol: TCP port: 80 targetPort: 8080 --- apiVersion: v1 kind: ServiceAccount metadata: name: static-server --- apiVersion: apps/v1 kind: Deployment metadata: name: static-server spec: replicas: 1 selector: matchLabels: app: static-server template: metadata: name: static-server labels: app: static-server annotations: 'consul.hashicorp.com/connect-inject': 'true' spec: containers: - name: static-server image: hashicorp/http-echo:latest args: - -text="hello world" - -listen=:8080 ports: - containerPort: 8080 name: http # If ACLs are enabled, the serviceAccountName must match the Consul service name. serviceAccountName: static-server ``` The only change for Connect is the addition of the `consul.hashicorp.com/connect-inject` annotation. This enables injection for the Pod in this Deployment. The injector can also be [configured](/docs/k8s/connect#installation-and-configuration) to automatically inject unless explicitly disabled, but the default installation requires opt-in using the annotation shown above. ~> **A common mistake** is to set the annotation on the Deployment or other resource. Ensure that the injector annotations are specified on the _pod specification template_ as shown above. This will start a sidecar proxy that listens on port `20000` registered with Consul and proxies valid inbound connections to port 8080 in the pod. To establish a connection to the pod using Connect, a client must use another Connect proxy. The client Connect proxy will use Consul service discovery to find all available upstream proxies and their public ports. In the example above, the server is listening on `:8080`. By default, the Consul Service Mesh runs in [transparent proxy](/docs/connect/transparent-proxy) mode. This means that even though the server binds to all interfaces, the inbound and outbound connections will automatically go through to the sidecar proxy. It also allows you to use Kubernetes DNS like you normally would without the Consul Service Mesh. -> **Note:** As of consul `v1.10.0`, consul-k8s `v0.26.0` and Consul Helm `v0.32.0`, all Consul Service Mesh services will run with transparent proxy enabled by default. Running with transparent proxy will enforce all inbound and outbound traffic to go through the Envoy proxy. The service name registered in Consul will be set to the name of the Kubernetes service associated with the Pod. This can be customized with the `consul.hashicorp.com/connect-service` annotation. If using ACLs, this name must be the same as the Pod's `ServiceAccount` name. ### Connecting to Connect-Enabled Services The example Deployment specification below configures a Deployment that is capable of establishing connections to our previous example "static-server" service. The connection to this static text service happens over an authorized and encrypted connection via Connect. -> **Note:** As of consul-k8s `v0.26.0` and Consul Helm `v0.32.0`, having a Kubernetes Service is **required** to run services on the Consul Service Mesh. ```yaml apiVersion: v1 kind: Service metadata: # This name will be the service name in Consul. name: static-client spec: selector: app: static-client ports: - port: 80 --- apiVersion: v1 kind: ServiceAccount metadata: name: static-client --- apiVersion: apps/v1 kind: Deployment metadata: name: static-client spec: replicas: 1 selector: matchLabels: app: static-client template: metadata: name: static-client labels: app: static-client annotations: 'consul.hashicorp.com/connect-inject': 'true' spec: containers: - name: static-client image: curlimages/curl:latest # Just spin & wait forever, we'll use `kubectl exec` to demo command: ['/bin/sh', '-c', '--'] args: ['while true; do sleep 30; done;'] # If ACLs are enabled, the serviceAccountName must match the Consul service name. serviceAccountName: static-client ``` By default when ACLs are enabled or when ACLs default policy is `allow`, Consul will automatically configure proxies with all upstreams from the same datacenter. When ACLs are enabled with default `deny` policy, you must supply an [intention](/docs/connect/intentions) to tell Consul which upstream you need to talk to. When upstreams are specified explicitly with the [`consul.hashicorp.com/connect-service-upstreams` annotation](/docs/k8s/connect#consul-hashicorp-com-connect-service-upstreams), the injector will also set environment variables `_CONNECT_SERVICE_HOST` and `_CONNECT_SERVICE_PORT` in every container in the Pod for every defined upstream. This is analogous to the standard Kubernetes service environment variables, but point instead to the correct local proxy port to establish connections via Connect. We can verify access to the static text server using `kubectl exec`. Because transparent proxy is enabled by default, we use Kubernetes DNS to connect to our desired upstream. ```shell-session $ kubectl exec deploy/static-client -- curl --silent http://static-server/ "hello world" ``` We can control access to the server using [intentions](/docs/connect/intentions). If you use the Consul UI or [CLI](/commands/intention/create) to create a deny [intention](/docs/connect/intentions) between "static-client" and "static-server", connections are immediately rejected without updating either of the running pods. You can then remove this intention to allow connections again. ```shell-session $ kubectl exec deploy/static-client -- curl --silent http://static-server/ command terminated with exit code 52 ``` ## Installation and Configuration The Connect sidecar proxy is injected via a [mutating admission webhook](https://kubernetes.io/docs/reference/access-authn-authz/extensible-admission-controllers/#admission-webhooks) provided by the [consul-k8s project](https://github.com/hashicorp/consul-k8s). This enables the automatic pod mutation shown in the usage section above. Installation of the mutating admission webhook is automated using the [Helm chart](/docs/k8s/installation/install). To install the Connect injector, enable the Connect injection feature using [Helm values](/docs/k8s/helm#configuration-values) and upgrade the installation using `helm upgrade` for existing installs or `helm install` for a fresh install. ```yaml connectInject: enabled: true controller: enabled: true ``` This will configure the injector to inject when the [injection annotation](#consul-hashicorp-com-connect-inject) is set to `true`. Other values in the Helm chart can be used to limit the namespaces the injector runs in, enable injection by default, and more. ### Controlling Injection Via Annotation By default, the injector will inject only when the [injection annotation](#consul-hashicorp-com-connect-inject) on the pod (not the deployment) is set to `true`: ```yaml annotations: 'consul.hashicorp.com/connect-inject': 'true' ``` ### Injection Defaults If you wish for the injector to always inject, you can set the default to `true` in the Helm chart: ```yaml connectInject: enabled: true default: true ``` You can then exclude specific pods via annotation: ```yaml annotations: 'consul.hashicorp.com/connect-inject': 'false' ``` ### Controlling Injection Via Namespace You can control which Kubernetes namespaces are allowed to be injected via the `k8sAllowNamespaces` and `k8sDenyNamespaces` keys: ```yaml connectInject: enabled: true k8sAllowNamespaces: ['*'] k8sDenyNamespaces: [] ``` In the default configuration (shown above), services from all namespaces are allowed to be injected. Whether or not they're injected depends on the value of `connectInject.default` and the `consul.hashicorp.com/connect-inject` annotation. If you wish to only enable injection in specific namespaces, you can list only those namespaces in the `k8sAllowNamespaces` key. In the configuration below only the `my-ns-1` and `my-ns-2` namespaces will be enabled for injection. All other namespaces will be ignored, even if the connect inject [annotation](#consul-hashicorp-com-connect-inject) is set. ```yaml connectInject: enabled: true k8sAllowNamespaces: ['my-ns-1', 'my-ns-2'] k8sDenyNamespaces: [] ``` If you wish to enable injection in every namespace _except_ specific namespaces, you can use `*` in the allow list to allow all namespaces and then specify the namespaces to exclude in the deny list: ```yaml connectInject: enabled: true k8sAllowNamespaces: ['*'] k8sDenyNamespaces: ['no-inject-ns-1', 'no-inject-ns-2'] ``` -> **NOTE:** The deny list takes precedence over the allow list. If a namespace is listed in both lists, it will **not** be synced. ~> **NOTE:** The `kube-system` and `kube-public` namespaces will never be injected. ### Consul Enterprise Namespaces Consul Enterprise 1.7+ supports Consul namespaces. When Kubernetes pods are registered into Consul, you can control which Consul namespace they are registered into. There are three options available: 1. **Single Destination Namespace** – Register all Kubernetes pods, regardless of namespace, into the same Consul namespace. This can be configured with: ```yaml global: enableConsulNamespaces: true connectInject: enabled: true consulNamespaces: consulDestinationNamespace: 'my-consul-ns' ``` -> **NOTE:** If the destination namespace does not exist we will create it. 1. **Mirror Namespaces** - Register each Kubernetes pod into a Consul namespace with the same name as its Kubernetes namespace. For example, pod `foo` in Kubernetes namespace `ns-1` will be synced to the Consul namespace `ns-1`. If a mirrored namespace does not exist in Consul, it will be created. This can be configured with: ```yaml global: enableConsulNamespaces: true connectInject: enabled: true consulNamespaces: mirroringK8S: true ``` 1. **Mirror Namespaces With Prefix** - Register each Kubernetes pod into a Consul namespace with the same name as its Kubernetes namespace **with a prefix**. For example, given a prefix `k8s-`, pod `foo` in Kubernetes namespace `ns-1` will be synced to the Consul namespace `k8s-ns-1`. This can be configured with: ```yaml global: enableConsulNamespaces: true connectInject: enabled: true consulNamespaces: mirroringK8S: true mirroringK8SPrefix: 'k8s-' ``` ### Consul Enterprise Namespace Upstreams When [transparent proxy](/docs/connect/transparent-proxy) is enabled and ACLs are disabled, the upstreams will be configured automatically across Consul namespaces. When ACLs are enabled, you must configure it by specifying an [intention](/docs/connect/intentions), allowing services across Consul namespaces to talk to each other. If you wish to specify an upstream explicitly via the `consul.hashicorp.com/connect-service-upstreams` annotation, use the format `[service-name].[namespace]:[port]:[optional datacenter]`: ```yaml annotations: 'consul.hashicorp.com/connect-inject': 'true' 'consul.hashicorp.com/connect-service-upstreams': '[service-name].[namespace]:[port]:[optional datacenter]' ``` See [consul.hashicorp.com/connect-service-upstreams](#consul-hashicorp-com-connect-service-upstreams) for more details. -> **Note:** When you specify upstreams via an upstreams annotation, you will need to use `localhost:` with the port from the upstreams annotation instead of KubeDNS to connect to your upstream application. ### Verifying the Installation To verify the installation, run the ["Accepting Inbound Connections"](/docs/k8s/connect#accepting-inbound-connections) example from the "Usage" section above. After running this example, run `kubectl get pod static-server --output yaml`. In the raw YAML output, you should see injected Connect containers and an annotation `consul.hashicorp.com/connect-inject-status` set to `injected`. This confirms that injection is working properly. If you do not see this, then use `kubectl logs` against the injector pod and note any errors.