Documentation for using and learning about Service Catalog.

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Design of the Service Catalog

This document covers the architecture and design of Service Catalog.

Table of Contents


The Service Catalog integrates with the Open Service Broker API (OSB API) to translate the Kubernetes resource model into OSB API calls to a service broker.

It has the following high level features:

These features provide a loose-coupling between Applications running in Kubernetes and services that they use.

Generally, the services that applications use are external (i.e. “black box”) to the Kubernetes cluster. For example, applications may decide to use a cloud database service.

Using Service Catalog and the appropriate service broker, application developers can focus on their own business logic, leave development and management of the service to someone else, and leave provisioning to the Service Catalog and broker.


Open Service Broker API

The Service Catalog is an Open Service Broker API (OSB API) client. The OSB API specification is the evolution of the Cloud Foundry Service Broker API.

We’re not going to detail the OSB API here; for more information, please see the Open Service Broker API Repository.

For the rest of this design document, we’ll assume that you’re familiar with the basic concepts of the OSB API.

Service Catalog Design

Service Catalog Design

The above is the high level architecture of Service Catalog. Service Catalog has two basic building blocks: a Webhook Server and a controller.

Webhook Server

The Webhook Server uses Admission Webhooks to manage custom resources. Admission Webhook is a feature available in the Kubernetes API Server, that allows you to implement arbitrary control decisions, such as validation or mutation.

For every resource managed by Service Catalog (the ones listed in the previous section), there is a separate handler defined. You can see the structure at pkg/webhook/servicecatalog. The current version of all Service Catalog API resources is v1beta1. The resources are defined here: pkg/apis/servicecatalog/v1beta1/types.go.

If you want to learn more about Admission Webhooks, read this document.


The Service Catalog controller implements the behaviors of the service-catalog API. It monitors the API resources (by watching the stream of events from the API server) and takes the appropriate actions to reconcile the current state with the user’s desired end state.

For example, if a user creates a ClusterServiceBroker, the Service Catalog controller will pick up the event and request the catalog from the broker listed in the resource.

For detailed information on a typical workflow, please see the walkthrough.

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