Auto-cleanup of k6 build cache (#1788)

* Auto-cleanup of k6 build cache

Signed-off-by: Pablo Chacin <pablochacin@gmail.com>

* Address review comments

Signed-off-by: Pablo Chacin <pablochacin@gmail.com>

---------

Signed-off-by: Pablo Chacin <pablochacin@gmail.com>

docs/modules/k6.md

@@ -62,13 +62,15 @@ k6.RunContainer(ctx, k6.SetEnvVar("URL","test.k6.io"), k6.WithTestScript("/tests
 
 #### WithCache
 
-Use `WithCache` passes a volume to be used as a [cache for building the k6 binary](https://github.com/szkiba/k6x#cache) inside the `k6` container.
-This option improves considerably the execution time of test suites that creates multiple `k6` test containers. 
-If the volume does not exits, it is created. The test is responsible for cleaning up this volume when no longer needed.
+Use `WithCache` sets a volume to be used as [cache for building the k6 binary](https://github.com/szkiba/k6x#cache) inside the `k6` container.
+This option improves considerably the execution time of test suites that creates multiple `k6` test containers.
 
+By default, a new volume is created and automatically removed when the test session ends.
+
+This is convenient for example for CI/CD environments. In other cases, such as local testing, it can be convenient to reuse the same cache volume across test sessions.In this cases, the TC_K6_BUILD_CACHE environment variables can used to provide the name of a volume to be used and kept across test sessions. If this volume does not exist, it will be created.
 
 ```golang
-k6.RunContainer(ctx, WithCache("cache"), k6.WithTestScript("/tests/test.js"))
+k6.RunContainer(ctx, WithCache(), k6.WithTestScript("/tests/test.js"))
 ```
 
 #### WithCmdOptions

modules/k6/examples_test.go

@@ -55,6 +55,7 @@ func ExampleRunContainer() {
 	// run the httpbin.js test scripts passing the IP address the httpbin container
 	k6, err := k6.RunContainer(
 		ctx,
+		k6.WithCache(),
 		k6.WithTestScript(absPath),
 		k6.SetEnvVar("HTTPBIN", httpbinIP),
 	)

modules/k6/k6.go

@@ -3,8 +3,11 @@ package k6
 import (
 	"context"
 	"fmt"
+	"os"
 	"path/filepath"
 
+	"github.com/docker/docker/api/types/mount"
+
 	"github.com/testcontainers/testcontainers-go"
 	"github.com/testcontainers/testcontainers-go/wait"
 )
@@ -49,13 +52,27 @@ func SetEnvVar(variable string, value string) testcontainers.CustomizeRequestOpt
 	}
 }
 
-// WithCache uses the given volume as a cache for building the k6 binary.
-// If the volume does not exists, it is created.
-func WithCache(cache string) testcontainers.CustomizeRequestOption {
+// WithCache sets a volume as a cache for building the k6 binary
+// If a volume name is provided in the TC_K6_BUILD_CACHE, this volume is used and it will
+// persist across test sessions.
+// If no value is provided, a volume is created and automatically deleted when the test session ends.
+func WithCache() testcontainers.CustomizeRequestOption {
+	var volOptions *mount.VolumeOptions
+
+	cacheVol := os.Getenv("TC_K6_BUILD_CACHE")
+	// if no volume is provided, create one and ensure add labels for garbage collection
+	if cacheVol == "" {
+		cacheVol = fmt.Sprintf("k6-cache-%s", testcontainers.SessionID())
+		volOptions = &mount.VolumeOptions{
+			Labels: testcontainers.GenericLabels(),
+		}
+	}
+
 	return func(req *testcontainers.GenericContainerRequest) {
 		mount := testcontainers.ContainerMount{
 			Source: testcontainers.DockerVolumeMountSource{
-				Name: cache,
+				Name:          cacheVol,
+				VolumeOptions: volOptions,
 			},
 			Target: "/cache",
 		}

modules/k6/k6_test.go

@@ -34,7 +34,7 @@ func TestK6(t *testing.T) {
 				t.Fatal(err)
 			}
 
-			container, err := RunContainer(ctx, WithTestScript(absPath))
+			container, err := RunContainer(ctx, WithCache(), WithTestScript(absPath))
 			if err != nil {
 				t.Fatal(err)
 			}