Kubernetes Service Binding Spec

Jeffrey Ellin

Why Service Bindings

Service Bindings

Kubernetes-wide specification for communicating service secrets to workloads in an automated way.

Concept adopted from Cloud Foundry and Heroku

Allows developers to focus on business value and not utility code

{Application Developer}

expects secrets to be exposed consistently and predictably

# Devloper

As a Developer I need a cloud agnostic way to consume credentials

Workload Projection

$SERVICE_BINDING_ROOT
├── account-database
│   ├── type
│   ├── provider
│   ├── uri
│   ├── username
│   └── password
└── transaction-event-stream
    ├── type
    ├── connection-count
    ├── uri
    ├── certificates
    └── private-key
# Developer
# Developer

Language Runtimes

Java Sample

import com.nebhale.bindings.Binding;
import com.nebhale.bindings.Bindings;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class Application {

    public static void main(String[] args) {
        Binding[] bindings = Bindings.fromServiceBindingRoot();
        bindings = Bindings.filter(bindings, "postgresql");
        if (bindings.length != 1) {
            System.err.printf("Incorrect number of PostgreSQL drivers: %d\n", bindings.length);
            System.exit(1);
        }

        String url = bindings[0].get("url");
        if (url == null) {
            System.err.println("No URL in binding");
            System.exit(1);
        }

        Connection conn;
        try {
            conn = DriverManager.getConnection(url);
        } catch (SQLException e) {
            System.err.printf("Unable to connect to database: %s", e);
            System.exit(1);
        }

        // ...
    }

}
# Developer

{Service Provider}

expects secrets to be collected consistently and predictably

Crossplane Composite Resource

apiVersion: example.dev/v1beta1
kind: Database
metadata:
  name: database-service
...
status:
  binding:
    name: production-db-secret
# Service Provider

Crossplane Secret

apiVersion: v1
kind: Secret
metadata:
  name: production-db-secret
stringData:
  type: mysql
  provider: bitnami
  host: localhost
  port: 3306
  username: root
  password: root
# Service Provider

Well Known Secret Entries

Apart from the special type, and provider entries in the Secret data, there are few special words called well-known entries.

Name Requirements
host A DNS-resolvable host name or IP address
port A valid port number
uri A valid URI as defined by RFC3986
username A string-based username credential
password A string-based password credential
certificates A collection of PEM-encoded X.509 certificates, representing a certificate chain used in mTLS client authentication
private-key A PEM-encoded private key used in mTLS client authentication
# Service Provider

{Application Operator}

expects secrets to be transferred from services to workloads consistently and predictably

Application operators bind application workloads with services by creating ServiceBinding resources.

kind: ServiceBinding

apiVersion: servicebinding.io/v1beta1
kind: ServiceBinding
metadata:
  name: account-service
spec:
  service:
    apiVersion: com.example/v1alpha1
    kind: AccountService
    name: prod-account-service
  workload:
    apiVersion: apps/v1
    kind: Deployment
    name: online-banking
# Application Operator

Multiple Workloads

apiVersion: servicebinding.io/v1beta1
kind: ServiceBinding
metadata:
  name: online-banking-frontend-to-account-service
spec:
  name: account-service
  service:
    apiVersion: com.example/v1alpha1
    kind: AccountService
    name: prod-account-service
  workload:
    apiVersion: apps/v1
    kind: Deployment
    selector:
      matchLabels:
        app.kubernetes.io/part-of: online-banking
        app.kubernetes.io/component: frontend
# Application Operator

Further Info

Crossplane   
       

ServiceBinding
Specification

Tanzu Application Platform

Further Info

https://slack.crossplane.io/

Kubernetes Service Bindings

By Jeffrey Ellin

Kubernetes Service Bindings

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