Envoy extensions overview

This topic provides an overview of Envoy extensions in Consul service mesh deployments. You can modify Consul-generated Envoy resources to add additional functionality without modifying the Consul codebase.

Introduction

Consul supports two methods for modifying Envoy behavior. You can either modify the Envoy resources Consul generates through escape hatches or configure your services to use Envoy extensions using the EnvoyExtension parameter. Implementing escape hatches requires rewriting the Envoy resources so that they are compatible with Consul, a task that also requires understanding how Consul names Envoy resources and enforces intentions.

Instead of modifying Consul code, you can configure your services to use Envoy extensions through the EnvoyExtensions field. This field is definable in proxy-defaults and service-defaults configuration entries.

Supported extensions

Envoy extensions enable additional service mesh functionality in Consul by changing how the sidecar proxies behave. Extensions invoke custom code when traffic passes through an Envoy proxy. Consul supports the following extensions:

• Lua
• Lambda

Lua

The lua Envoy extension enables HTTP Lua filters in your Consul Envoy proxies. It allows you to run Lua scripts during Envoy requests and responses from Consul-generated Envoy resources. Refer to the lua documentation for more information.

Lambda

The lambda Envoy extension enables services to make requests to AWS Lambda functions through the mesh as if they are a normal part of the Consul catalog. Refer to the lambda documentation for more information.