istio

Thu, 25 Sep 2025 15:28:48 +0800

istio/istio

Istio

Istio is an open source service mesh that layers transparently onto existing distributed applications. Istio’s powerful features provide a uniform and more efficient way to secure, connect, and monitor services. Istio is the path to load balancing, service-to-service authentication, and monitoring – with few or no service code changes.

For in-depth information about how to use Istio, visit istio.io
To ask questions and get assistance from our community, visit Github Discussions
To learn how to participate in our overall community, visit our community page

In this README:

In addition, here are some other documents you may wish to read:

Istio Community - describes how to get involved and contribute to the Istio project
Istio Developer’s Guide - explains how to set up and use an Istio development environment
Project Conventions - describes the conventions we use within the code base
Creating Fast and Lean Code - performance-oriented advice and guidelines for the code base

You’ll find many other useful documents on our Wiki.

Introduction

Istio is an open platform for providing a uniform way to integrate microservices, manage traffic flow across microservices, enforce policies and aggregate telemetry data. Istio’s control plane provides an abstraction layer over the underlying cluster management platform, such as Kubernetes.

Istio is composed of these components:

Envoy - Sidecar proxies per microservice to handle ingress/egress traffic between services in the cluster and from a service to external services. The proxies form a secure microservice mesh providing a rich set of functions like discovery, rich layer-7 routing, circuit breakers, policy enforcement and telemetry recording/reporting functions.

Note: The service mesh is not an overlay network. It simplifies and enhances how microservices in an application talk to each other over the network provided by the underlying platform.
Istiod - The Istio control plane. It provides service discovery, configuration and certificate management. It consists of the following sub-components:
- Pilot - Responsible for configuring the proxies at runtime.
- Citadel - Responsible for certificate issuance and rotation.
- Galley - Responsible for validating, ingesting, aggregating, transforming and distributing config within Istio.
Operator - The component provides user friendly options to operate the Istio service mesh.

Repositories

The Istio project is divided across a few GitHub repositories:

istio/api. This repository defines component-level APIs and common configuration formats for the Istio platform.
istio/community. This repository contains information on the Istio community, including the various documents that govern the Istio open source project.
istio/istio. This is the main code repository. It hosts Istio’s core components, install artifacts, and sample programs. It includes:
- istioctl. This directory contains code for the istioctl command line utility.
- pilot. This directory contains platform-specific code to populate the abstract service model, dynamically reconfigure the proxies when the application topology changes, as well as translate routing rules into proxy specific configuration.
- security. This directory contains security related code, including Citadel (acting as Certificate Authority), citadel agent, etc.
istio/proxy. The Istio proxy contains extensions to the Envoy proxy (in the form of Envoy filters) that support authentication, authorization, and telemetry collection.
istio/ztunnel. The repository contains the Rust implementation of the ztunnel component of Ambient mesh.
istio/client-go. This repository defines auto-generated Kubernetes clients for interacting with Istio resources programmatically.

[!NOTE] Only the istio/api and istio/client-go repositories expose stable interfaces intended for direct usage as libraries.

Issue management

We use GitHub to track all of our bugs and feature requests. Each issue we track has a variety of metadata:

Epic. An epic represents a feature area for Istio as a whole. Epics are fairly broad in scope and are basically product-level things. Each issue is ultimately part of an epic.
Milestone. Each issue is assigned a milestone. This is 0.1, 0.2, …, or ‘Nebulous Future’. The milestone indicates when we think the issue should get addressed.
Priority. Each issue has a priority which is represented by the column in the Prioritization project. Priority can be one of P0, P1, P2, or >P2. The priority indicates how important it is to address the issue within the milestone. P0 says that the milestone cannot be considered achieved if the issue isn’t resolved.