K3s¶

Introduction¶

The Testcontainers module for K3s.

Adding this module to your project dependencies¶

Please run the following command to add the K3s module to your Go dependencies:

go get github.com/testcontainers/testcontainers-go/modules/k3s

Usage example¶

Test for a K3s container

package k3s_test

import (
    "context"
    "fmt"
    "testing"
    "time"

    "github.com/stretchr/testify/require"
    corev1 "k8s.io/api/core/v1"
    metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    kwait "k8s.io/apimachinery/pkg/util/wait"
    "k8s.io/client-go/kubernetes"
    "k8s.io/client-go/tools/clientcmd"

    "github.com/testcontainers/testcontainers-go"
    "github.com/testcontainers/testcontainers-go/modules/k3s"
    "github.com/testcontainers/testcontainers-go/wait"
)

func Test_LoadImages(t *testing.T) {
    // Give up to three minutes to run this test
    ctx, cancel := context.WithDeadline(context.Background(), time.Now().Add(3*time.Minute))
    defer cancel()

    k3sContainer, err := k3s.Run(ctx, "rancher/k3s:v1.27.1-k3s1")
    testcontainers.CleanupContainer(t, k3sContainer)
    require.NoError(t, err)

    kubeConfigYaml, err := k3sContainer.GetKubeConfig(ctx)
    require.NoError(t, err)

    restcfg, err := clientcmd.RESTConfigFromKubeConfig(kubeConfigYaml)
    require.NoError(t, err)

    k8s, err := kubernetes.NewForConfig(restcfg)
    require.NoError(t, err)

    provider, err := testcontainers.ProviderDocker.GetProvider()
    require.NoError(t, err)

    // ensure nginx image is available locally
    err = provider.PullImage(ctx, "nginx")
    require.NoError(t, err)

    t.Run("Test load image not available", func(t *testing.T) {
        err := k3sContainer.LoadImages(ctx, "fake.registry/fake:non-existing")
        require.Error(t, err)
    })

    t.Run("Test load image in cluster", func(t *testing.T) {
        err := k3sContainer.LoadImages(ctx, "nginx")
        require.NoError(t, err)

        pod := &corev1.Pod{
            TypeMeta: metav1.TypeMeta{
                Kind:       "Pod",
                APIVersion: "v1",
            },
            ObjectMeta: metav1.ObjectMeta{
                Name: "test-pod",
            },
            Spec: corev1.PodSpec{
                Containers: []corev1.Container{
                    {
                        Name:            "nginx",
                        Image:           "nginx",
                        ImagePullPolicy: corev1.PullNever, // use image only if already present
                    },
                },
            },
        }

        _, err = k8s.CoreV1().Pods("default").Create(ctx, pod, metav1.CreateOptions{})
        require.NoError(t, err)

        err = kwait.PollUntilContextCancel(ctx, time.Second, true, func(ctx context.Context) (bool, error) {
            state, err := getTestPodState(ctx, k8s)
            if err != nil {
                return false, err
            }
            if state.Terminated != nil {
                return false, fmt.Errorf("pod terminated: %v", state.Terminated)
            }
            return state.Running != nil, nil
        })
        require.NoError(t, err)

        state, err := getTestPodState(ctx, k8s)
        require.NoError(t, err)
        require.NotNil(t, state.Running)
    })
}

func getTestPodState(ctx context.Context, k8s *kubernetes.Clientset) (corev1.ContainerState, error) {
    var pod *corev1.Pod
    var err error
    pod, err = k8s.CoreV1().Pods("default").Get(ctx, "test-pod", metav1.GetOptions{})
    if err != nil || len(pod.Status.ContainerStatuses) == 0 {
        return corev1.ContainerState{}, err
    }
    return pod.Status.ContainerStatuses[0].State, nil
}

func Test_APIServerReady(t *testing.T) {
    ctx := context.Background()

    k3sContainer, err := k3s.Run(ctx, "rancher/k3s:v1.27.1-k3s1")
    testcontainers.CleanupContainer(t, k3sContainer)
    require.NoError(t, err)

    kubeConfigYaml, err := k3sContainer.GetKubeConfig(ctx)
    require.NoError(t, err)

    restcfg, err := clientcmd.RESTConfigFromKubeConfig(kubeConfigYaml)
    require.NoError(t, err)

    k8s, err := kubernetes.NewForConfig(restcfg)
    require.NoError(t, err)

    pod := &corev1.Pod{
        TypeMeta: metav1.TypeMeta{
            Kind:       "Pod",
            APIVersion: "v1",
        },
        ObjectMeta: metav1.ObjectMeta{
            Name: "test-pod",
        },
        Spec: corev1.PodSpec{
            Containers: []corev1.Container{
                {
                    Name:  "nginx",
                    Image: "nginx",
                },
            },
        },
    }

    _, err = k8s.CoreV1().Pods("default").Create(context.Background(), pod, metav1.CreateOptions{})
    require.NoError(t, err)
}

func Test_WithManifestOption(t *testing.T) {
    ctx := context.Background()

    k3sContainer, err := k3s.Run(ctx,
        "rancher/k3s:v1.27.1-k3s1",
        k3s.WithManifest("nginx-manifest.yaml"),
        testcontainers.WithAdditionalWaitStrategy(wait.ForExec([]string{"kubectl", "wait", "pod", "nginx", "--for=condition=Ready"})),
    )
    testcontainers.CleanupContainer(t, k3sContainer)
    require.NoError(t, err)
}

Module Reference¶

Run function¶

Since v0.32.0

Info

The RunContainer(ctx, opts...) function is deprecated and will be removed in the next major release of Testcontainers for Go.

The K3s module exposes one entrypoint function to create the K3s container, and this function receives three parameters:

func Run(ctx context.Context, img string, opts ...testcontainers.ContainerCustomizer) (*K3sContainer, error)

context.Context, the Go context.
string, the Docker image to use.
testcontainers.ContainerCustomizer, a variadic argument for passing options.

Container Ports¶

These are the ports used by the K3s container:

Container Ports

defaultKubeSecurePort     = "6443/tcp"
defaultRancherWebhookPort = "8443/tcp"

Image¶

Use the second argument in the Run function to set a valid Docker image. In example: Run(context.Background(), "rancher/k3s:v1.27.1-k3s1").

Container Options¶

When starting the K3s container, you can pass options in a variadic way to configure it.

WithManifest¶

Since v0.29.0

The WithManifest option loads a manifest obtained from a local file into the cluster. K3s applies it automatically during the startup process

func WithManifest(manifestPath string) testcontainers.CustomizeRequestOption

Example:

        WithManifest("nginx-manifest.yaml")

The following options are exposed by the testcontainers package.

Basic Options¶

WithExposedPorts Since v0.37.0
WithEnv Since v0.29.0
WithWaitStrategy Since v0.20.0
WithAdditionalWaitStrategy Since v0.38.0
WithWaitStrategyAndDeadline Since v0.20.0
WithAdditionalWaitStrategyAndDeadline Since v0.38.0
WithEntrypoint Since v0.37.0
WithEntrypointArgs Since v0.37.0
WithCmd Since v0.37.0
WithCmdArgs Since v0.37.0
WithLabels Since v0.37.0

Lifecycle Options¶

WithLifecycleHooks Since v0.38.0
WithAdditionalLifecycleHooks Since v0.38.0
WithStartupCommand Since v0.25.0
WithAfterReadyCommand Since v0.28.0

Files & Mounts Options¶

Build Options¶

WithDockerfile Since v0.37.0

Logging Options¶

Image Options¶

Networking Options¶

Advanced Options¶

WithHostPortAccess Since v0.31.0
WithConfigModifier Since v0.20.0
WithHostConfigModifier Since v0.20.0
WithEndpointSettingsModifier Since v0.20.0
CustomizeRequest Since v0.20.0
WithName Since v0.38.0
WithNoStart Since v0.38.0
WithProvider Not available until the next release main

Experimental Options¶

WithReuseByName Since v0.37.0

Container Methods¶

The K3s container exposes the following methods:

GetKubeConfig¶

Since v0.21.0

The GetKubeConfig method returns the K3s cluster's kubeconfig, including the server URL, to be used for connecting to the Kubernetes Rest Client API using a Kubernetes client. It'll be returned in the format of []bytes.

Get KubeConfig

package k3s_test

import (
    "context"
    "fmt"
    "log"

    v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
    "k8s.io/client-go/kubernetes"
    "k8s.io/client-go/tools/clientcmd"

    "github.com/testcontainers/testcontainers-go"
    "github.com/testcontainers/testcontainers-go/modules/k3s"
)

func ExampleRun() {
    // runK3sContainer {
    ctx := context.Background()

    k3sContainer, err := k3s.Run(ctx, "rancher/k3s:v1.27.1-k3s1")
    defer func() {
        if err := testcontainers.TerminateContainer(k3sContainer); err != nil {
            log.Printf("failed to terminate container: %s", err)
        }
    }()
    if err != nil {
        log.Printf("failed to start container: %s", err)
        return
    }
    // }

    state, err := k3sContainer.State(ctx)
    if err != nil {
        log.Printf("failed to get container state: %s", err)
        return
    }

    fmt.Println(state.Running)

    kubeConfigYaml, err := k3sContainer.GetKubeConfig(ctx)
    if err != nil {
        log.Printf("failed to get kubeconfig: %s", err)
        return
    }

    restcfg, err := clientcmd.RESTConfigFromKubeConfig(kubeConfigYaml)
    if err != nil {
        log.Printf("failed to create rest config: %s", err)
        return
    }

    k8s, err := kubernetes.NewForConfig(restcfg)
    if err != nil {
        log.Printf("failed to create k8s client: %s", err)
        return
    }

    nodes, err := k8s.CoreV1().Nodes().List(ctx, v1.ListOptions{})
    if err != nil {
        log.Printf("failed to list nodes: %s", err)
        return
    }

    fmt.Println(len(nodes.Items))

    // Output:
    // true
    // 1
}

LoadImages¶

Since v0.25.0

The LoadImages method loads a list of images into the kubernetes cluster and makes them available to pods.

This is useful for testing images generated locally without having to push them to a public docker registry or having to configure k3s to use a private registry.

The images must be already present in the node running the test. DockerProvider offers a method for pulling images, which can be used from the test code to ensure the image is present locally before loading them to the cluster.