kopia/internal/cache/cache_storage.go

package cache

import (
	"context"
	"os"
	"path/filepath"
	"time"

	"github.com/pkg/errors"

	"github.com/kopia/kopia/internal/ctxutil"
	"github.com/kopia/kopia/repo/blob"
	"github.com/kopia/kopia/repo/blob/filesystem"
)

// DirMode is the directory mode for all caches.
const DirMode = 0o700

// Storage is the storage interface required by the cache and is implemented by the filesystem Storage.
type Storage interface {
	blob.Storage
	TouchBlob(ctx context.Context, contentID blob.ID, threshold time.Duration) error
}

// NewStorageOrNil returns cache.Storage backed by the provided directory.
func NewStorageOrNil(ctx context.Context, cacheDir string, maxBytes int64, subdir string) (Storage, error) {
	if maxBytes <= 0 || cacheDir == "" {
		return nil, nil
	}

	if !filepath.IsAbs(cacheDir) {
		return nil, errors.Errorf("cache dir %q was not absolute", cacheDir)
	}

	contentCacheDir := filepath.Join(cacheDir, subdir)

	if _, err := os.Stat(contentCacheDir); os.IsNotExist(err) {
		if mkdirerr := os.MkdirAll(contentCacheDir, DirMode); mkdirerr != nil {
			return nil, errors.Wrap(mkdirerr, "error creating cache directory")
		}
	}

	fs, err := filesystem.New(ctxutil.Detach(ctx), &filesystem.Options{
		Path:            contentCacheDir,
		DirectoryShards: []int{2},
	})
	if err != nil {
		return nil, errors.Wrap(err, "error initializing filesystem cache")
	}

	return fs.(Storage), nil
}