zrepl/zfs/replication_history.go

package zfs

import (
	"fmt"

	"github.com/pkg/errors"
)

const ReplicationCursorBookmarkName = "zrepl_replication_cursor"

// may return nil for both values, indicating there is no cursor
func ZFSGetReplicationCursor(fs *DatasetPath) (*FilesystemVersion, error) {
	versions, err := ZFSListFilesystemVersions(fs, nil)
	if err != nil {
		return nil, err
	}
	for _, v := range versions {
		if v.Type == Bookmark && v.Name == ReplicationCursorBookmarkName {
			return &v, nil
		}
	}
	return nil, nil
}

func ZFSSetReplicationCursor(fs *DatasetPath, snapname string) (guid uint64, err error) {
	snapPath := fmt.Sprintf("%s@%s", fs.ToString(), snapname)
	debug("replication cursor: snap path %q", snapPath)
	snapProps, err := ZFSGetCreateTXGAndGuid(snapPath)
	if err != nil {
		return 0, errors.Wrapf(err, "get properties of %q", snapPath)
	}
	bookmarkPath := fmt.Sprintf("%s#%s", fs.ToString(), ReplicationCursorBookmarkName)
	propsBookmark, err := ZFSGetCreateTXGAndGuid(bookmarkPath)
	_, bookmarkNotExistErr := err.(*DatasetDoesNotExist)
	if err != nil && !bookmarkNotExistErr {
		return 0, errors.Wrap(err, "zfs: replication cursor: get bookmark txg")
	}
	if err == nil {
		if snapProps.CreateTXG < propsBookmark.CreateTXG {
			return 0, errors.New("zfs: replication cursor: can only be advanced, not set back")
		}
		if err := ZFSDestroy(bookmarkPath); err != nil { // FIXME make safer by using new temporary bookmark, then rename, possible with channel programs
			return 0, errors.Wrap(err, "zfs: replication cursor: destroy current cursor")
		}
	}
	if err := ZFSBookmark(fs, snapname, ReplicationCursorBookmarkName); err != nil {
		return 0, errors.Wrapf(err, "zfs: replication cursor: create bookmark")
	}
	return snapProps.Guid, nil
}