e2e_dra: use latest release if stable doesn't exist

This change updates the DRA upgrade/downgrade test to attempt
downloading the "latest" Kubernetes release if the "stable" release
entry point is not available.

This should fix test failures for the time just before the release,
when master is switched to the next release, but stable release URL
is not yet updated.

Author: bart0sh

test/e2e_dra/upgradedowngrade_test.go

@@ -62,6 +62,8 @@ import (
 	admissionapi "k8s.io/pod-security-admission/api"
 )
 
+var errHTTP404 = errors.New("resource not found (404)")
+
 func init() {
 	// -v=5 may be useful to debug driver operations, but usually isn't needed.
 	ktesting.SetDefaultVerbosity(2)
@@ -121,6 +123,7 @@ var _ = ginkgo.Describe("DRA upgrade/downgrade", func() {
 		version, err := version.ParseGeneric(gitVersion)
 		tCtx.ExpectNoError(err, "parse version %s of repo root %q", gitVersion, repoRoot)
 		major, previousMinor := version.Major(), version.Minor()-1
+		tCtx.Logf("got version: major: %d, minor: %d, previous minor: %d", major, version.Minor(), previousMinor)
 		tCtx = ktesting.End(tCtx)
 
 		// KUBERNETES_SERVER_CACHE_DIR can be set to keep downloaded files across test restarts.
@@ -130,8 +133,18 @@ var _ = ginkgo.Describe("DRA upgrade/downgrade", func() {
 		}
 		haveBinaries := false
 
-		// Get the previous release, if necessary.
-		previousURL, previousVersion := serverDownloadURL(tCtx, major, previousMinor)
+		// Get the previous release.
+		tCtx = ktesting.Begin(tCtx, "get previous release info")
+		tCtx.Logf("stable release %d.%d", major, previousMinor)
+		previousURL, previousVersion, err := serverDownloadURL(tCtx, "stable", major, previousMinor)
+		if errors.Is(err, errHTTP404) {
+			tCtx.Logf("stable doesn't exist, get latest release %d.%d", major, previousMinor)
+			previousURL, previousVersion, err = serverDownloadURL(tCtx, "latest", major, previousMinor)
+		}
+		tCtx.ExpectNoError(err)
+		tCtx.Logf("got previous release version: %s, URL: %s", previousVersion, previousURL)
+		tCtx = ktesting.End(tCtx)
+
 		if cacheBinaries {
 			binDir = path.Join(binDir, previousVersion)
 			_, err := os.Stat(path.Join(binDir, string(localupcluster.KubeClusterComponents[0])))
@@ -299,6 +312,7 @@ func sourceVersion(tCtx ktesting.TContext, kubeRoot string) (gitVersion string,
 	if err != nil {
 		return "", "", err
 	}
+	tCtx.Logf("workspace status:\n%s", output)
 
 	// Parse it.
 	for _, line := range strings.Split(string(output), "\n") {
@@ -355,29 +369,54 @@ func sourceVersion(tCtx ktesting.TContext, kubeRoot string) (gitVersion string,
 // 	return output.String()
 // }
 
-// serverDownloadURL returns the full URL for a kubernetes-server archive matching
-// the current GOOS/GOARCH for the given major/minor version of Kubernetes.
+// serverDownloadURL constructs a download URL for a Kubernetes server tarball based on the given
+// prefix, major, and minor version numbers. It performs an HTTP GET request to retrieve the version
+// string from a remote text file, then builds the final tarball URL using the retrieved version,
+// the current OS, and architecture. If the version file is not found (HTTP 404), it returns
+// errHTTP404 to allow the caller to try another prefix. Returns the tarball URL, the version string,
+// or an error if any step fails.
+// The function uses the provided testing context for logging and error handling.
+//
+// Parameters:
+//   - tCtx: a ktesting.TContext used for test context and error handling.
+//   - prefix: the release prefix (e.g., "stable", "latest").
+//   - major: the major version number.
+//   - minor: the minor version number.
 //
-// This considers only proper releases.
-func serverDownloadURL(tCtx ktesting.TContext, major, minor uint) (string, string) {
+// Returns:
+//   - The constructed tarball download URL as a string.
+//   - The version string as retrieved from the remote file.
+//   - An error if the request fails, the response is invalid, or the version file is not found.
+func serverDownloadURL(tCtx ktesting.TContext, prefix string, major, minor uint) (string, string, error) {
 	tCtx.Helper()
-	url := fmt.Sprintf("https://dl.k8s.io/release/stable-%d.%d.txt", major, minor)
+	url := fmt.Sprintf("https://dl.k8s.io/release/%s-%d.%d.txt", prefix, major, minor)
 	get, err := http.NewRequestWithContext(tCtx, http.MethodGet, url, nil)
-	tCtx.ExpectNoError(err, "construct GET for %s", url)
+	if err != nil {
+		return "", "", fmt.Errorf("constructing GET for %s failed: %w", url, err)
+	}
 	resp, err := http.DefaultClient.Do(get)
-	tCtx.ExpectNoError(err, "get %s", url)
+	if err != nil {
+		return "", "", fmt.Errorf("downloading %s failed: %w", url, err)
+	}
+	if resp.StatusCode == http.StatusNotFound {
+		// Caller should be able to distinguish HTTP 404
+		// to try another prefix (usually 'latest' if 'stable' returns 404)
+		return "", "", errHTTP404
+	}
 	if resp.StatusCode != http.StatusOK {
-		tCtx.Fatalf("get %s: %d - %s", url, resp.StatusCode, resp.Status)
+		return "", "", fmt.Errorf("getting %s failed: status code: %d, status: %s", url, resp.StatusCode, resp.Status)
 	}
 	if resp.Body == nil {
-		tCtx.Fatalf("empty response for %s", url)
+		return "", "", fmt.Errorf("empty response for %s", url)
 	}
 	defer func() {
 		tCtx.ExpectNoError(resp.Body.Close(), "close response body")
 	}()
 	version, err := io.ReadAll(resp.Body)
-	tCtx.ExpectNoError(err, "read response body for %s", url)
-	return fmt.Sprintf("https://dl.k8s.io/release/%s/kubernetes-server-%s-%s.tar.gz", string(version), runtime.GOOS, runtime.GOARCH), string(version)
+	if err != nil {
+		return "", "", fmt.Errorf("reading response body for %s failed: %w", url, err)
+	}
+	return fmt.Sprintf("https://dl.k8s.io/release/%s/kubernetes-server-%s-%s.tar.gz", string(version), runtime.GOOS, runtime.GOARCH), string(version), nil
 }
 
 // testResourceClaimDeviceStatus corresponds to testResourceClaimDeviceStatus in test/integration/dra