---
layout: docs
page_title: API Gateway
description: Using Consul API gateway functionality
---

# Consul API Gateway

This topic describes how to use the Consul API Gateway add-on module, which helps users control access to services running within a Consul service mesh. The API gateway enables external network clients to access applications and services running in a Consul datacenter. This type of network traffic is commonly referred to as "north-south" network traffic as it refers to the flow of data into and out of a specific environment. Requests from clients can also be forwarded based on path or request protocol.

## Introduction

Consul API Gateway is an implementation of the Kubernetes Gateway [API Specification](https://gateway-api.sigs.k8s.io/). This specification defines a set of custom resource definitions (CRD) that can create logical gateways and routes based on the path or protocol of a client request. Consul API Gateway solves two primary use cases:

- **Controlling access at the point entry**: Consul API Gateway allows users to set the protocols of external connection requests and provide clients with TLS certificates from trusted providers (e.g., VeriSign, Let’sEncrypt).
- **Simplifying traffic management**: The Consul API Gateway can load balance requests across services and route traffic to the appropriate service based on matching one or more criteria, such as hostname, path, header presence or value, and HTTP Method type (e.g., GET, POST, PATCH).

## Requirements

Your datacenter must meet the following requirements prior to configuring the Consul API Gateway:

- A Kubernetes cluster must be running
- Consul 1.11.2+

## Installation

1. Create a values file for your Consul server agents that contains the following parameters:

  <CodeBlockConfig hideClipboard filename="values.yaml">

  ```yaml
  global:
    name: consul
    image: 'hashicorp/consul:1.11.2'
    tls:
      enabled: true
  connectInject:
    enabled: true
  controller:
    enabled: true
  ```

  </CodeBlockConfig>

1. Install Consul API Gateway using the standard Consul Helm chart and specify the custom values file.

  ```shell-session
  $ helm install consul hashicorp/consul --version 0.39.0 --values values.yaml
  ```

  The following components will be installed:

    - Gateway controller
    - CRDs required by the Kubernetes Gateway API specification
    - `kustomize` manifests for completing the installation

1. After `helm` installs Consul API Gateway packages, issue the following commands to apply the API gateway to your Kubernetes cluster.

```shell-session
$ kubectl apply --kustomize="github.com/hashicorp/consul-api-gateway/config/crd?ref=v0.1.0-beta"
$ kubectl apply --kustomize="github.com/hashicorp/consul-api-gateway/config?ref=v0.1.0-beta"
```

## Usage

1. Verify that the [requirements](#requirements) have been met.
1. Verify that the Consul API Gateway software has been installed and applied (see [Installation](#installation)).
1. Configure the gateway, listener(s), and route(s) as described in [Configuration](#configuration)
1. Issue the `kubectl apply` command to implement the configurations, e.g.:

```shell-session
$ kubectl apply --values gateway-configuration.yaml
```

<!--- Commented out per https://github.com/hashicorp/consul/pull/11951/files#r791204596

### Using the Consul API Gateway Binary

You can download the Consul API Gateway binary and use it to manually start the control plane server.

1. Download the binary from the [Consul API Gateway repository](https://github.com/hashicorp/consul-api-gateway).
1. Navigate to the `consul-api-gateway-main` directory and build the binary:

```shell-session
$ go build
```

1.  (Optional) Copy the binary to the execution path, e.g.:

```shell-session
$ cp consul-api-gateway /usr/bin
```

1.  Use the `server` command to interact with the Consul API Gateway binary:

```shell-session
$ ./consul-api-gateway server <options>
```

The following options are supported:

| Option                 | Description                                                                                                                                                                           | Required | Default                                                                 |
| ---------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------- | ----------------------------------------------------------------------- |
| `-ca-file`             | String value that specifies the path to the CA for the Consul server.                                                                                                                 | Required | none                                                                    |
| `-ca-secret`           | String value that specifies the CA secret for the Consul server.                                                                                                                      | Required | none                                                                    |
| `-ca-secret-namespace` | String value that specifies the CA secret namespace for the Consul server.                                                                                                            | Required | none                                                                    |
| `-k8-context`          | String value that specifies the Kubernetes context to use when starting the Consul server.                                                                                            | Optional | current context                                                         |
| `-k8-namespace`        | String value that specifies the Kubernetes namespace to use when starting the Consul server.                                                                                          | Optional | `default`                                                               |
| `-log-json`            | Boolean value that enables or disables JSON format for the log output.                                                                                                                | Required | `false`                                                                 |
| `-log-level`           | String value that specifies the logging level. The following values are supported: <br/>- `trace` (highest level of detail) <br/>- `debug` <br/>- `info` <br/>- `warn` <br/>- `error` | Optional | `info`                                                                  |
| `-metrics-port`        | Integer value that specifies the port number for collecting metrics.                                                                                                                  | Optional | none                                                                    |
| `-pprof`               | Integer value that specifies the Go pprof port number for collecting metrics.                                                                                                         | Optional | none                                                                    |
| `-sds-server-host`     | String value that specifies the host server for the secret discovery service (SDS).                                                                                                   | Optional | `consul-api-gateway-controller.default.`<br/>`svc.cluster.`<br/>`local` |
| `-sds-server-host`     | Integer value that specifies the port number for the secret discovery service (SDS).                                                                                                  | Optional | `9090`                                                                  |

You can also issue the `version` command to print the Consul API Gateway version to the console:

```shell-session
$ ./consul-api-gateway version
consul-api-gateway 0.1.0
```
--->

## Configuration

Configure the following artifacts to facilitate ingress into your Consul service mesh:

- [Gateway](#gateway): Defines the main infrastructure resource that links API gateway components. It specifies the name of the `GatewayClass` and one or more `listeners`.
- [GatewayClass](#gatewayclass): Defines a class of gateway resources that you can use as a template for creating gateways.
- [GatewayClassConfig](#gatewayclassconfig): Describes additional Consul API Gatway-related configuration parameters for the `GatewayClass` resource.
- [Listeners](#listeners): Defines listener properties, such as protocol, port, and namespace.
- [Routes](#routes): Specifies the path from the client to the listener.

### Gateway

The gateway configuration is the main infrastructure resource that links API gateway components. It specifies the name of the `GatewayClass` and one or more `listeners`.

Add the `kind: Gateway` option to the configuration file to declare a gateway.
The following example creates a gateway called `example-gateway`.
The gateway is based on the `test-gateway-class` and includes a listener called `https` (see [Listeners](#listeners) for details about the `listener` configuration).

<CodeBlockConfig filename="gateway.yaml" lineNumbers highlight="2,4,8,9,13">

```yaml
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: Gateway
metadata:
  name: example-gateway
  annotations:
    'external-dns.alpha.kubernetes.io/hostname': DNS_HOSTNAME
spec:
  gatewayClassName: test-gateway-class
  listeners:
    - protocol: HTTPS
      hostname: DNS_HOSTNAME
      port: 443
      name: https
      allowedRoutes:
        namespaces:
          from: Same
      tls:
        certificateRefs:
          - name: gateway-production-certificate
```

</CodeBlockConfig>

Refer to the Kubernetes Gateway API documentation for details about configuring gateways:
<https://gateway-api.sigs.k8s.io/v1alpha2/references/spec/#gateway.networking.k8s.io/v1alpha2.Gateway>

### GatewayClass

The `GatewayClass` resource is used as a template for creating `Gateway` resources.
The specification includes the name of the controller (`controllerName`) and an API object containing controller-specific configuration resource within the cluster (`parametersRef`).

When gateways are created from a `GatewayClass`, they use the parameters specified in the `GatewayClass` at the time of instantiation.
If you want to propagate changes made to the `GatewayClass` after gateways have been created, then the implementation must document this behavior.
The `gateway-exists-finalizer.gateway.networking.k8s.io` finalizer must also be added to a `GatewayClass` to ensure that a `GatewayClass` associated with a `Gateway` is not deleted while in use.

Add the `kind: GatewayClass` option to the the gateway values file to declare a gateway class.
The following example creates a gateway class called `test-gateway-class`.

<CodeBlockConfig filename="gateway.yaml">

```yaml
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: GatewayClass
metadata:
  name: test-gateway-class
spec:
  controllerName: 'hashicorp.com/consul-api-gateway-controller'
  parametersRef:
    group: api-gateway.consul.hashicorp.com
    kind: GatewayClassConfig
    name: test-gateway-class-config
```

</CodeBlockConfig>

Refer to the Kubernetes Gateway API documentation for details about configuring gateway classes:
<https://gateway-api.sigs.k8s.io/v1alpha2/references/spec/#gateway.networking.k8s.io/v1alpha2.GatewayClass>

### GatewayClassConfig

The `GatewayClassConfig` object describes additional Consul API Gateway-related configuration parameters for the `GatewayClass`.

Add the `kind: GatewayClassConfig` option to the gateway values file to declare a gateway class.
The following example creates a gateway class called `test-gateway-class-config`.

<CodeBlockConfig filename="gateway.yaml">

```yaml
apiVersion: api-gateway.consul.hashicorp.com/v1alpha1
kind: GatewayClassConfig
metadata:
  name: test-gateway-class-config
spec:
  useHostPorts: true
  logLevel: trace
  consul:
    scheme: https
    caSecret: consul-ca-cert
    ports:
      http: 8501
      grpc: 8502
```

</CodeBlockConfig>

The following table describes the required parameters for the `spec` array:

| Parameter      | Description                                                                                                                                          | Type    | Default |
| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- | ------- | ------- |
| `useHostPorts` | Enables the gateway to use the host ports                                                                                                            | Boolean | `true`  |
| `logLevel`     | Specifies the error reporting level for logs. You can specify the following values: `FATAL`, `ERROR`, `WARN`, `INFO`, `DEBUG`, `TRACE`, `ALL`, `OFF` | String  | `trace` |
| `consul`       | Specifies ingress properties for Consul. See [Consul Configuration](#consul-configuration)                                                           | Array   | N/A     |

#### Consul Configuration

The following table describes the parameters available for the `consul` element of the `GatewayClassConfiguration`:

| Parameter  | Description                                                   | Type   | Default                         |
| ---------- | ------------------------------------------------------------- | ------ | ------------------------------- |
| `scheme`   | Specifies the message protocol.                               | String | `http`                          |
| `caSecret` | Specifies the name of the CA secret.                          | String | none                            |
| `ports`    | Specifies which ports to use for API and application traffic. | Array  | `http: 8501` <br/> `grpc: 8502` |

### Listeners

Listeners are the logical endpoints bound to the gateway's addresses.
Add the `listener` object to the `gateway` configuration and specify the following properties to define a listener:

- `hostname`: Hostname specifies the virtual hostname to match for protocol types.
- `port`: Specifies the network port.
- `protocol`: Specifies the network protocol expected by the listener.

Refer to the Kubernetes Gateway API documentation for details about configuring listeners:
<https://gateway-api.sigs.k8s.io/v1alpha2/references/spec/#gateway.networking.k8s.io/v1alpha2.Listener>

In the example included the [Gateway](#gateway) description, a listener named `https` that listens over `HTTPS` is configured to listen on port `443`

### Route

Routes are independent configuration objects that are associated with specific listeners.
Use the `kind: HTTPRoute` option to declare a route and use the `spec` option to specify the route details.
The following example creates a route named `example-route` associated with a listener defined in `example-gateway`.

```yaml
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: HTTPRoute
metadata:
  name: example-route
spec:
  parentRefs:
    - name: example-gateway
  rules:
    - backendRefs:
        - kind: Service
          name: echo
          port: 8080
```
