Fence installation transaction durability (T-613)

core/installer/durability.go

@@ -0,0 +1,99 @@
+package installer
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"sort"
+)
+
+var ErrDurability = errors.New("install durability fence failed")
+
+type durabilityFence interface {
+	syncFile(file *os.File) error
+	syncDirectory(path string) error
+}
+
+type filesystemDurability struct{}
+
+func (filesystemDurability) syncFile(file *os.File) error {
+	return file.Sync()
+}
+
+func (filesystemDurability) syncDirectory(path string) error {
+	return syncDirectoryPath(path)
+}
+
+func defaultDurability() durabilityFence {
+	return filesystemDurability{}
+}
+
+func effectiveDurability(fence durabilityFence) durabilityFence {
+	if fence == nil {
+		return defaultDurability()
+	}
+	return fence
+}
+
+func syncFileWithFence(fence durabilityFence, file *os.File, description string) error {
+	if err := effectiveDurability(fence).syncFile(file); err != nil {
+		return fmt.Errorf("%w: sync %s: %v", ErrDurability, description, err)
+	}
+	return nil
+}
+
+func syncDirectoryWithFence(fence durabilityFence, path, description string) error {
+	if err := effectiveDurability(fence).syncDirectory(path); err != nil {
+		return fmt.Errorf("%w: sync %s: %v", ErrDurability, description, err)
+	}
+	return nil
+}
+
+func syncStagingTree(fence durabilityFence, root string) error {
+	directories := make([]string, 0)
+	err := filepath.WalkDir(root, func(path string, entry fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if entry.Type()&os.ModeSymlink != 0 {
+			return fmt.Errorf("%w: staging tree contains a symbolic link", ErrUnsafeInstallLayout)
+		}
+		if entry.IsDir() {
+			directories = append(directories, path)
+		}
+		return nil
+	})
+	if err != nil {
+		return fmt.Errorf("%w: walk staging tree: %w", ErrDurability, err)
+	}
+	sort.Slice(directories, func(left, right int) bool {
+		return len(directories[left]) > len(directories[right])
+	})
+	for _, directory := range directories {
+		if err := syncDirectoryWithFence(fence, directory, "staging directory"); err != nil {
+			return err
+		}
+	}
+	parent := filepath.Dir(root)
+	if parent != root {
+		if err := syncDirectoryWithFence(fence, parent, "staging parent directory"); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func renameManagedDirectory(
+	layout appLayout,
+	source string,
+	target string,
+	fence durabilityFence,
+	description string,
+) error {
+	if err := os.Rename(source, target); err != nil {
+		return err
+	}
+	return syncDirectoryWithFence(fence, layout.root, description)
+}