Extensibility on Envoy Gateway

Build a Wasm image

Mon, 01 Jan 0001 00:00:00 +0000

Envoy Gateway supports two types of Wasm extensions within the EnvoyExtensionPolicy API: HTTP Wasm Extensions and Image Wasm Extensions. Packaging a Wasm extension as an OCI image is beneficial because it simplifies versioning and distribution for users. Additionally, users can leverage existing image toolchain to build and manage Wasm images.

This document describes how to build OCI images which are consumable by Envoy Gateway.

Wasm Image Formats

There are two types of images that are supported by Envoy Gateway. One is in the Docker format, and another is the standard OCI specification compliant format. Please note that both of them are supported by any OCI registries. You can choose either format depending on your preference, and both types of images are consumable by Envoy Gateway EnvoyExtensionPolicy API.

Envoy Patch Policy

Mon, 01 Jan 0001 00:00:00 +0000

This task explains the usage of the EnvoyPatchPolicy API. Note: This API is meant for users extremely familiar with Envoy xDS semantics. Also before considering this API for production use cases, please be aware that this API is unstable and the outcome may change across versions. Use at your own risk.

Introduction

The EnvoyPatchPolicy API allows user to modify the output xDS configuration generated by Envoy Gateway intended for EnvoyProxy, using JSON Patch semantics.

Envoy Gateway Extension Server

Mon, 01 Jan 0001 00:00:00 +0000

This task explains how to extend Envoy Gateway using an Extension Server. Envoy Gateway can be configured to call an external server over gRPC with the xDS configuration before it is sent to Envoy Proxy. The external server can modify the provided configuration programmatically using any semantics supported by the xDS API.

Using an extension server allows vendors to add xDS configuration that Envoy Gateway itself doesn’t support with a very high level of control over the generated xDS configuration.

External Processing

Mon, 01 Jan 0001 00:00:00 +0000

This task provides instructions for configuring external processing.

External processing calls an external gRPC service to process HTTP requests and responses. The external processing service can inspect and mutate requests and responses.

Envoy Gateway introduces a new CRD called EnvoyExtensionPolicy that allows the user to configure external processing. This instantiated resource can be linked to a Gateway and HTTPRoute resource.

Prerequisites

Follow the steps below to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTP.

Lua Extensions

Mon, 01 Jan 0001 00:00:00 +0000

This task provides instructions for extending Envoy Gateway with Lua extensions.

Lua extensions allow you to extend the functionality of Envoy Gateway by running custom code against HTTP requests and responses, without modifying the Envoy Gateway binary. These comparatively light-weight extensions are written in the Lua scripting language using APIs defined here.

Envoy Gateway allows the user to configure Lua extensions using the EnvoyExtensionPolicy CRD. This instantiated resource can be linked to a Gateway or HTTPRoute resource. If linked to both, the resource linked to the route takes precedence over those linked to Gateway.

Wasm Extensions

Mon, 01 Jan 0001 00:00:00 +0000

This task provides instructions for extending Envoy Gateway with WebAssembly (Wasm) extensions.

Wasm extensions allow you to extend the functionality of Envoy Gateway by running custom code against HTTP requests and responses, without modifying the Envoy Gateway binary. These extensions can be written in any language that compiles to Wasm, such as C++, Rust, AssemblyScript, or TinyGo.

Envoy Gateway introduces a new CRD called EnvoyExtensionPolicy that allows the user to configure Wasm extensions. This instantiated resource can be linked to a Gateway and HTTPRoute resource.