Perf | Reuse branch stream for Kustomize refs

pkg/reposerverextract/extract.go

@@ -726,6 +726,16 @@ func buildManifestRequestForSource(
 		return request, "", nil, nil
 	}
 
+	// Kustomize can reference directories outside the source path. Stream the
+	// existing checkout directly, as on the no-refs path, so those directories
+	// remain available without creating and recompressing a per-request copy of
+	// the whole checkout. Ref sources are only used by Helm value files and file
+	// parameters, so a Kustomize source does not need the .refs staging tree.
+	srcContentDir := filepath.Join(branchFolder, primarySource.Path)
+	if isKustomizeSource(srcContentDir) {
+		return newManifestRequest(&primarySource), branchFolder, nil, nil
+	}
+
 	//   <tempDir>/<primarySource.Path>/  ← content source files
 	//   <tempDir>/.refs/<refName>/       ← files for each ref source
 	tempDir, err := os.MkdirTemp("", "argocd-diff-preview-*")
@@ -738,20 +748,11 @@ func buildManifestRequestForSource(
 		}
 	}
 
-	// Kustomize can reference files outside the source dir, so stage the
-	// whole checkout (like the no-refs fast path).
-	srcContentDir := filepath.Join(branchFolder, primarySource.Path)
-	if isKustomizeSource(srcContentDir) {
-		if err := stageCheckout(branchFolder, tempDir); err != nil {
-			cleanup()
-			return nil, "", nil, fmt.Errorf("failed to stage branch folder %q: %w", branchFolder, err)
-		}
-	} else {
-		dstContentDir := filepath.Join(tempDir, primarySource.Path)
-		if err := copyDir(srcContentDir, dstContentDir); err != nil {
-			cleanup()
-			return nil, "", nil, fmt.Errorf("failed to copy content source dir %q: %w", srcContentDir, err)
-		}
+	// Copy the content source directory into the temp tree.
+	dstContentDir := filepath.Join(tempDir, primarySource.Path)
+	if err := copyDir(srcContentDir, dstContentDir); err != nil {
+		cleanup()
+		return nil, "", nil, fmt.Errorf("failed to copy content source dir %q: %w", srcContentDir, err)
 	}
 
 	// Copy only the ref files used by this content source into
@@ -1124,41 +1125,6 @@ func hasExternalRefSource(refSources []v1alpha1.ApplicationSource, repoSelector
 	return false
 }
 
-// stageCheckout mirrors a checkout into dst: files are hardlinked (staging
-// is read-only), symlinks stay symlinks, .git is skipped. Links are left for
-// the repo server and kustomize to validate, like on a real clone.
-func stageCheckout(src, dst string) error {
-	return filepath.Walk(src, func(srcPath string, info os.FileInfo, err error) error {
-		if err != nil {
-			return err
-		}
-		if info.IsDir() && info.Name() == ".git" {
-			return filepath.SkipDir
-		}
-		rel, err := filepath.Rel(src, srcPath)
-		if err != nil {
-			return err
-		}
-		dstPath := filepath.Join(dst, rel)
-		switch {
-		case info.IsDir():
-			return os.MkdirAll(dstPath, 0o755)
-		case info.Mode()&os.ModeSymlink != 0:
-			target, err := os.Readlink(srcPath)
-			if err != nil {
-				return err
-			}
-			return os.Symlink(target, dstPath)
-		default:
-			// parent dirs already exist: Walk visits directories first
-			if err := os.Link(srcPath, dstPath); err == nil {
-				return nil
-			}
-			return copyFile(srcPath, dstPath)
-		}
-	})
-}
-
 // copyDir recursively copies src into dst, creating dst if needed.
 func copyDir(src, dst string) error {
 	return filepath.Walk(src, func(srcPath string, info os.FileInfo, err error) error {

pkg/reposerverextract/extract_test.go

@@ -540,10 +540,11 @@ spec:
 	assertDefaultProjectFields(t, req)
 }
 
-// Multi-source: a kustomize content source referencing files outside its own
-// directory must stage the whole checkout (like the no-refs fast path), or
-// the escaping reference fails with "no such file or directory".
-func TestBuildManifestRequest_MultiSource_Kustomize_WithRef_StagesBranchRoot(t *testing.T) {
+// Multi-source: a kustomize content source referencing a directory outside its
+// own path must stream the existing checkout, like the no-refs path. Besides
+// keeping the referenced directory available, reusing this path lets the tgz
+// cache share one compressed checkout across applications.
+func TestBuildManifestRequest_MultiSource_Kustomize_WithRef_StreamsBranchRoot(t *testing.T) {
 	branchFolder := t.TempDir()
 	require.NoError(t, os.MkdirAll(filepath.Join(branchFolder, "clusters", "dev", "my-app"), 0o755))
 	require.NoError(t, os.WriteFile(
@@ -581,42 +582,12 @@ spec:
 		repoSelector: testRepoSelector(t, ""),
 	})
 	require.NoError(t, err)
-	require.NotEmpty(t, streamDir)
-	defer cleanup()
+	assert.Equal(t, branchFolder, streamDir)
+	assert.Nil(t, cleanup)
 
 	assert.Equal(t, "clusters/dev/my-app", req.ApplicationSource.Path)
 	_, statErr := os.Stat(filepath.Join(streamDir, "base", "my-app", "kustomization.yaml"))
-	assert.NoError(t, statErr, "files referenced outside the kustomize source dir must be staged")
-}
-
-// symlinks stay symlinks (the repo server and kustomize validate them, like
-// on a real clone), files are hardlinked, .git is skipped
-func TestStageCheckout_PreservesSymlinksAndHardlinks(t *testing.T) {
-	src := t.TempDir()
-	require.NoError(t, os.WriteFile(filepath.Join(src, "app.yaml"), []byte("a: 1"), 0o644))
-	require.NoError(t, os.MkdirAll(filepath.Join(src, ".git"), 0o755))
-	require.NoError(t, os.WriteFile(filepath.Join(src, ".git", "HEAD"), []byte("ref"), 0o644))
-	require.NoError(t, os.Symlink("app.yaml", filepath.Join(src, "link-in.yaml")))
-	require.NoError(t, os.Symlink("../outside.yaml", filepath.Join(src, "link-out.yaml")))
-
-	dst := filepath.Join(t.TempDir(), "dst")
-	require.NoError(t, stageCheckout(src, dst))
-
-	// symlinks preserved verbatim, including ones pointing outside the tree
-	target, err := os.Readlink(filepath.Join(dst, "link-in.yaml"))
-	require.NoError(t, err)
-	assert.Equal(t, "app.yaml", target)
-	target, err = os.Readlink(filepath.Join(dst, "link-out.yaml"))
-	require.NoError(t, err)
-	assert.Equal(t, "../outside.yaml", target)
-
-	// regular files hardlinked, .git skipped
-	srcInfo, err := os.Stat(filepath.Join(src, "app.yaml"))
-	require.NoError(t, err)
-	dstInfo, err := os.Stat(filepath.Join(dst, "app.yaml"))
-	require.NoError(t, err)
-	assert.True(t, os.SameFile(srcInfo, dstInfo), "regular files should be hardlinked")
-	assert.NoDirExists(t, filepath.Join(dst, ".git"))
+	assert.NoError(t, statErr, "directories referenced outside the kustomize source path must remain available")
 }
 
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