The Service Binding Operator

Connecting Applications with Services on Kubernetes and OpenShift

Introduction

The goal of the Service Binding Operator is to enable application authors to import an application and run it on Kubernetes with services such as databases represented as Kubernetes objects including Operator-backed and chart-based backing services, without having to perform manual configuration of Secrets, ConfigMaps, etc.

To make a service bindable, the service provider needs to express the information needed by applications to bind with the services. In other words, the service provider must express the information that's “interesting” to applications.

There are multiple methods for making backing services bindable, including the backing service provider providing metadata as annotations on the resource. Details on the methods for making backing services bindable are available in the User Guide.

To make an imported application (for example, a NodeJS application) connect to a backing service (for example, a database):

The app author (developer) creates a ServiceBinding and specifies:
- The resource that needs the binding information. The resource can be specified by label selectors;
- The backing service's resource reference that the imported application needs to be bound to;
The Service Binding Controller then:
- Reads backing service operator CRD annotations to discover the binding attributes
- Creates a binding secret for the backing service, example, an operator-managed database;
- Injects environment variables into the applications' Deployment, DeploymentConfig, Replicaset, KnativeService or anything that uses a standard PodSpec;

Key Features

Support Binding with backing services represented by Kubernetes resources including third-party CRD-backed resources.
Support binding with multiple-backing services.
Extract binding information based on annotations present in CRDs/CRs/resources.
Extract binding values based on annotations present in OLM descriptors.
Project binding values as volume mounts.
Project binding values as environment variables.
Binding of PodSpec-based workloads.
Binding of non-PodSpec-based Kubernetes resources.
Custom binding variables composed from one or more backing services.
Auto-detect binding resources in the absence of binding decorators.

Example

Binding a Java Application with a Database

apiVersion: binding.operators.coreos.com/v1alpha1
kind: ServiceBinding
metadata:
  name: binding-request
  namespace: service-binding-demo
spec:
  application:
    name: java-app
    group: apps
    version: v1
    resource: deployments
  services:
  - group: postgresql.baiju.dev
    version: v1alpha1
    kind: Database
    name: db-demo
    id: postgresDB

User guide

Dependencies

Dependency	Supported versions
Kubernetes	v1.17.* or higher.

Quick Start

Installing in a Cluster

Follow OperatorHub instructions.

Running Operator Locally

Clone the repository and run make run using an existing kube:admin kube context.

Key Features

Support Binding with backing services represented by Kubernetes resources including third-party CRD-backed resources.
Support binding with multiple-backing services.
Extract binding information based on annotations present in CRDs/CRs/resources.
Extract binding values based on annotations present in OLM descriptors.
Project binding values as volume mounts.
Project binding values as environment variables.
Binding of PodSpec-based workloads.
Binding of non-PodSpec-based Kubernetes resources.
Custom binding variables composed from one or more backing services.
Auto-detect binding resources in the absence of binding decorators.

Getting Started

The best way to get started with the Service Binding Operator is to see it in action.

A number of example scenarios for using the operator are included in this repo. The examples are found in the "/examples" directory. Each of these examples illustrates a usage scenario for the operator. Each example also includes a README file with step-by-step instructions for how to run the example.

The following section in this README file includes links to the current set of examples.