Technical Overview

Before beginning with the practice labs, it is is very advisable to explain a brief technical overview of Istio.

Most of this content is taken directly from the official Istio documentation.

What is Istio?

At a high level, Istio helps reduce the complexity of these deployments, and eases the strain on your development teams. It is a completely open source service mesh that layers transparently onto existing distributed applications. It is also a platform, including APIs that let it integrate into any logging platform, or telemetry or policy system. Istio’s diverse feature set lets you successfully, and efficiently, run a distributed microservice architecture, and provides a uniform way to secure, connect, and monitor microservices.

What is a service mesh?

Istio addresses the challenges developers and operators face as monolithic applications transition towards a distributed microservice architecture. To see how, it helps to take a more detailed look at Istio’s service mesh.

The term service mesh is used to describe the network of microservices that make up such applications and the interactions between them. As a service mesh grows in size and complexity, it can become harder to understand and manage. Its requirements can include discovery, load balancing, failure recovery, metrics, and monitoring. A service mesh also often has more complex operational requirements, like A/B testing, canary rollouts, rate limiting, access control, and end-to-end authentication.

Istio provides behavioral insights and operational control over the service mesh as a whole, offering a complete solution to satisfy the diverse requirements of microservice applications.

Why use Istio?

Istio makes it easy to create a network of deployed services with load balancing, service-to-service authentication, monitoring, and more, with few or no code changes in service code. You add Istio support to services by deploying a special sidecar proxy throughout your environment that intercepts all network communication between microservices, then configure and manage Istio using its control plane functionality, which includes:

• Automatic load balancing for HTTP, gRPC, WebSocket, and TCP traffic.
• Fine-grained control of traffic behavior with rich routing rules, retries, failovers, and fault injection.
• A pluggable policy layer and configuration API supporting access controls, rate limits and quotas.
• Automatic metrics, logs, and traces for all traffic within a cluster, including cluster ingress and egress.
• Secure service-to-service communication in a cluster with strong identity-based authentication and authorization.

Core features

Some of the key capabilities provided by Istio are:

Traffic management

Istio’s easy rules configuration and traffic routing lets you control the flow of traffic and API calls between services. Istio simplifies configuration of service-level properties like circuit breakers, timeouts, and retries, and makes it a breeze to set up important tasks like A/B testing, canary rollouts, and staged rollouts with percentage-based traffic splits.

With better visibility into your traffic, and out-of-box failure recovery features, you can catch issues before they cause problems, making calls more reliable, and your network more robust – no matter what conditions you face.

Security

Istio’s security capabilities free developers to focus on security at the application level. Istio provides the underlying secure communication channel, and manages authentication, authorization, and encryption of service communication at scale. With Istio, service communications are secured by default, letting you enforce policies consistently across diverse protocols and runtimes – all with little or no application changes.

While Istio is platform independent, using it with Kubernetes (or infrastructure) network policies, the benefits are even greater, including the ability to secure pod-to-pod or service-to-service communication at the network and application layers.

Observability

Istio’s robust tracing, monitoring, and logging features give you deep insights into your service mesh deployment. Gain a real understanding of how service performance impacts things upstream and downstream with Istio’s monitoring features, while its custom dashboards provide visibility into the performance of all your services and let you see how that performance is affecting your other processes.

All these features let you more effectively set, monitor, and enforce SLOs on services. Of course, the bottom line is that you can detect and fix issues quickly and efficiently.

Architecture

An Istio service mesh is logically split into a data plane and a control plane.

• The data plane is composed of a set of intelligent proxies (Envoy) deployed as sidecars. These proxies mediate and control all network communication between microservices along with Mixer, a general-purpose policy and telemetry hub.
• The control plane manages and configures the proxies to route traffic. Additionally, the control plane configures Mixers to enforce policies and collect telemetry.

The following diagram shows the different components that make up each plane:

Components

The following sections provide a brief overview of each of Istio's core components.

Envoy

Istio uses an extended version of the Envoy proxy. Envoy is a high-performance proxy developed in C++ to mediate all inbound and outbound traffic for all services in the service mesh. Envoy proxies are the only Istio components that interact with data plane traffic.

Envoy proxies are deployed as sidecars to services, logically augmenting the services with Envoy’s many built-in features, for example:

Some of the Istio features and tasks enabled by Envoy proxies include:

• Traffic control features: enforce fine-grained traffic control with rich routing rules for HTTP, gRPC, WebSocket, and TCP traffic.
• Network resiliency features: setup retries, failovers, circuit breakers, and fault injection.
• Security and authentication features: enforce security policies and enforce access control and rate limiting defined through the configuration API.

Mixer

Mixer is a platform-independent component. Mixer enforces access control and usage policies across the service mesh, and collects telemetry data from the Envoy proxy and other services. The proxy extracts request level attributes, and sends them to Mixer for evaluation. You can find more information on this attribute extraction and policy evaluation in our Mixer Configuration documentation.

Pilot

Pilot provides service discovery for the Envoy sidecars, traffic management capabilities for intelligent routing (e.g., A/B tests, canary rollouts, etc.), and resiliency (timeouts, retries, circuit breakers, etc.).

Pilot converts high level routing rules that control traffic behavior into Envoy-specific configurations, and propagates them to the sidecars at runtime. Pilot abstracts platform-specific service discovery mechanisms and synthesizes them into a standard format that any sidecar conforming with the Envoy API can consume.

Citadel

Citadel enables strong service-to-service and end-user authentication with built-in identity and credential management. You can use Citadel to upgrade unencrypted traffic in the service mesh. Using Citadel, operators can enforce policies based on service identity rather than on relatively unstable layer 3 or layer 4 network identifiers. Starting from release 0.5, you can use Istio's authorization feature to control who can access your services.

Galley

Galley is Istio's configuration validation, ingestion, processing and distribution component. It is responsible for insulating the rest of the Istio components from the details of obtaining user configuration from the underlying platform (e.g. Kubernetes).