servicebinding

Kubernetes Service Binding Library for Go Applications

The Service Binding Specification for Kubernetes standardizes exposing backing service secrets to applications. This project provides a Go package to consume the bindings projected into the container. The Application Projection section of the spec describes how the bindings are projected into the application. The primary mechanism of projection is through files mounted at a specific directory. The bindings directory path can be discovered through SERVICE_BINDING_ROOT environment variable. The operator must have injected SERVICE_BINDING_ROOT environment to all the containers where bindings are created.

Within this service binding root directory, there could be multiple bindings projected from different Service Bindings. For example, suppose an application requires to connect to a database and cache server. In that case, one Service Binding can provide the database, and the other Service Binding can offer bindings to the cache server.

Let's take a look at the example given in the spec:

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

In the above example, there are two bindings under the SERVICE_BINDING_ROOT directory. The account-database and transaction-event-system are the names of the bindings. Files within each bindings directory has a special file named type, and you can rely on the value of that file to identify the type of the binding projected into that directory. In certain directories, you can also see another file named provider. The provider is an additional identifier to narrow down the type further. This package use the type field and, optionally, provider field to look up the bindings.

Installation

You can download the pacakge using go get:

go get github.com/baijum/servicebinding

Usage

You can import the binding package like this:

import "github.com/baijum/servicebinding/binding"

You can create *ServiceBinding object like this:

sb, err := NewServiceBinding()

To get bindings for a specific type, say postgresql:

bindings, err := sb.Bindings("postgresql")

To get bindings for a specific type, say mysql, and provider, say mariadb:

bindings, err := sb.BindingsWithProvider("mysql", "mariadb")

To get all bindings irrespective of the type and provider:

bindings, err := sb.AllBindings()

This is the complete ServiceBinding interface:

type ServiceBinding interface {

	// AllBindings get all bndings as a sice of map[string]string.
	// Return empty slice if no bindings found.
	AllBindings() ([]map[string]string, error)

	// Bindings get the bindings for a given type as a slice of
	// map[string]string.
	// Return empty slice if no bindings found
	Bindings(_type string) ([]map[string]string, error)

	// BindingsWithProvider get the bindings for a given type and provider
	// as a slice of map[string]string.
	// Return empty slice if no bindings found.
	BindingsWithProvider(_type, provider string) ([]map[string]string, error)
}