#Understanding Envoy Gateway

#Terminology

• Envoy Gateway is an open-source project for managing Envoy Proxy as a standalone or Kubernetes-based application gateway.
• Gateway API is a Kubernetes-official collection of CRDs for declaring routing rules and traffic management policies. Envoy Gateway is one implementation of the Gateway API specification.
• Gateway or gatewayapi/gateway is a CR defined by the Gateway API specification.
• envoy-gateway instance is Envoy Gateway instance and all its related resources running in a Kubernetes cluster.
• envoy-gateway-operator is a helm-operator wrapper around Envoy Gateway and use EnvoyGatewayCtl to simplify the deployment and management of envoy-gateway instance.
• EnvoyProxy is a CR defined by the Envoy Gateway specification, used by envoy-gateway instance to manage envoy-proxy instance.
• envoy-proxy instance is a running deployment which handles incoming traffic.

#Architecture

1. After installing the envoy-gateway-operator, it watch EnvoyGatewayCtl and deploys an envoy-gateway instance along with a default GatewayClass.

2. When you create a Gateway that references this GatewayClass and specifies an EnvoyProxy configuration, the envoy-gateway instance deploys an envoy-proxy instance to handle incoming traffic.

3. HTTP, TCP, or UDP Route resources can then be created and attached to this Gateway to define traffic routing policies.

4. For more granular configuration, you can create ClientTrafficPolicy or BackendTrafficPolicy resources and attach them to routes to implement advanced traffic management features.

#Related CRDs

Envoy Gateway and envoy-gateway-operator introduce additional CRDs that, combined with the Gateway API CRDs, comprehensively control all aspects of gateway deployment and routing policy configurations.

#Gateway API Related CRDs

CRD	Description
GatewayClass	An envoy-gateway instance knows which GatewayClasses it manages, and thereby knows which Gateways it should control.
Gateway	Defines three essential components: 1. GatewayClass reference - References the GatewayClass that controls this Gateway via .spec.gatewayClassName 2. Listeners configuration - Specifies which ports, hostnames, and TLS certificates to use for traffic handling via .spec.listeners 3. Infrastructure parameters - Configures deployment specifics like replicas, resources by referencing an EnvoyProxy via .spec.infrastructure.parametersRef
HTTP/TCP/UDP Route	Defines four essential components: 1. Multiple matching rule sets - Various conditions to match incoming traffic 2. Backend destinations - Target services for each matching rule set 3. Traffic policies - Per-rule configurations including retries, timeouts, redirects, etc. 4. Gateway listeners attachment - Defined via .spec.parentRefs to connect routes to specific Gateway listeners

For more details about these resources, please refer to the Gateway API Concepts.

#Envoy Gateway Related CRDs

CRD	Description
EnvoyProxy	Defines the configuration for envoy-proxy instances, such as replicas, resources, and scheduling constraints

In the recommended deployment pattern, each Gateway uses .spec.infrastructure.parametersRef to reference its own dedicated EnvoyProxy resource.

This one-to-one mapping allows users to control the Gateway's deployment configuration (replicas, resources, scheduling, etc.) by modifying the corresponding EnvoyProxy resource.

#Operator Related CRD

CRD	Description
EnvoyGatewayCtl	Controls the deployment of a specific envoy-gateway instance.

We recommend deploying a single envoy-gateway instance via EnvoyGatewayCtl per cluster, which is sufficient for typical use cases.

However, the EnvoyGatewayCtl resource allows you to deploy multiple envoy-gateway instance within the same cluster, enabling more flexible control and isolation for advanced scenarios such as different deployment mode

#Next Steps

Install Envoy Gateway via Operator

#Additional resources:

Resource	Description
Envoy Gateway	Official documentation for Envoy Gateway
Gateway API	Official documentation for Gateway API
Install Envoy Gateway via Operator	Guide for installing Envoy Gateway using the operator
Configure GatewayAPI Gateway	Guide for configuring Gateway in our platform via web console or yaml
Configure GatewayAPI Route	Guide for configuring Route in our platform via web console or yaml
Tasks for Envoy Gateway	Common tasks and operations for Envoy Gateway