go-sdk

A lightweight Go SDK for use within OpenFaaS functions and to control the OpenFaaS gateway.

For use within any Go code (not just OpenFaaS Functions):

• Client - A client for the OpenFaaS REST API

For use within functions:

• ReadSecret() - Read a named secret from within an OpenFaaS Function
• ReadSecrets() - Read all available secrets returning a queryable map

Authentication helpers (See: Authentication with IAM):

• ServiceAccountTokenSource - An implementation of the TokenSource interface to get an ID token by reading a Kubernetes projected service account token from /var/secrets/tokens/openfaas-token or the path set by the token_mount_path environment variable.

Usage

import "github.com/openfaas/go-sdk"

Construct a new OpenFaaS client and use it to access the OpenFaaS gateway API.

gatewayURL, _ := url.Parse("http://127.0.0.1:8080")
auth := &sdk.BasicAuth{
    Username: username,
    Password: password,
}

client := sdk.NewClient(gatewayURL, auth, http.DefaultClient)

namespace, err := client.GetNamespaces(context.Background())

Authentication with IAM

To authenticate with an OpenFaaS deployment that has Identity and Access Management (IAM) enabled, the client needs to exchange an ID token for an OpenFaaS ID token.

To get a token that can be exchanged for an OpenFaaS token you need to implement the TokenSource interface.

This is an example of a token source that gets a service account token mounted into a pod with ServiceAccount token volume projection.

type ServiceAccountTokenSource struct{}

func (ts *ServiceAccountTokenSource) Token() (string, error) {
	tokenMountPath := getEnv("token_mount_path", "/var/secrets/tokens")
	if len(tokenMountPath) == 0 {
		return "", fmt.Errorf("invalid token_mount_path specified for reading the service account token")
	}

	idTokenPath := path.Join(tokenMountPath, "openfaas-token")
	idToken, err := os.ReadFile(idTokenPath)
	if err != nil {
		return "", fmt.Errorf("unable to load service account token: %s", err)
	}

	return string(idToken), nil
}

The service account token returned by the TokenSource is automatically exchanged for an OpenFaaS token that is then used in the Authorization header for all requests made to the API.

If the OpenFaaS token is expired the TokenSource is asked for a token and the token exchange will run again.

gatewayURL, _ := url.Parse("https://gw.openfaas.example.com")

auth := &sdk.TokenAuth{
    TokenURL "https://gw.openfaas.example.com/oauth/token",
    TokenSource: &ServiceAccountTokenSource{}
}

client := sdk.NewClient(gatewayURL, auth, http.DefaultClient)

Authentication with Federated Gateway

func Test_ClientCredentials(t *testing.T) {
	clientID := ""
	clientSecret := ""
	tokenURL := "https://keycloak.example.com/realms/openfaas/protocol/openid-connect/token"
	scope := "email"
	grantType := "client_credentials"

	audience = "" // Optional

	auth := NewClientCredentialsTokenSource(clientID, clientSecret, tokenURL, scope, grantType, audience)

	token, err := auth.Token()
	if err != nil {
		t.Fatal(err)
	}

	if token == "" {
		t.Fatal("token is empty")
	}

	u, _ := url.Parse("https://fed-gw.example.com")

	client := NewClient(u, &ClientCredentialsAuth{tokenSource: auth}, http.DefaultClient)

	fns, err := client.GetFunctions(context.Background(), "openfaas-fn")
	if err != nil {
		t.Fatal(err)
	}

	if len(fns) == 0 {
		t.Fatal("no functions found")
	}
}

Deploy Function

status, err := client.Deploy(context.Background(), types.FunctionDeployment{
	Service:    "env-store-test",
	Image:      "ghcr.io/openfaas/alpine:latest",
	Namespace:  "openfaas-fn",
	EnvProcess: "env",
})

// non 200 status value will have some error
if err != nil {
	log.Printf("Deploy Failed: %s", err)
}

Delete Function

err := client.DeleteFunction(context.Background(),"env-store-test", "openfaas-fn")
if err != nil {
	log.Printf("Deletion Failed: %s", err)
}

License

License: MIT