backupstorage

type BackupHandle interface {
	// Bucket is the location of the backup. Will contain keyspace/shard.
	Bucket() string

	// Name is the individual name of the backup. Will contain
	// tabletAlias-timestamp.
	Name() string

	// AddFile opens a new file to be added to the backup.
	// Only works for read-write backups (created by StartBackup).
	// filename is guaranteed to only contain alphanumerical
	// characters and hyphens.
	// It should be thread safe, it is possible to call AddFile in
	// multiple go routines once a backup has been started.
	AddFile(filename string) (io.WriteCloser, error)

	// EndBackup stops and closes a backup. The contents should be kept.
	// Only works for read-write backups (created by StartBackup).
	EndBackup() error

	// AbortBackup stops a backup, and removes the contents that
	// have been copied already. It is called if an error occurs
	// while the backup is being taken, and the backup cannot be finished.
	// Only works for read-write backups (created by StartBackup).
	AbortBackup() error

	// ReadFile starts reading a file from a backup.
	// Only works for read-only backups (created by ListBackups).
	ReadFile(filename string) (io.ReadCloser, error)
}

type BackupStorage interface {
	// ListBackups returns all the backups in a bucket.  The
	// returned backups are read-only (ReadFile can be called, but
	// AddFile/EndBackup/AbortBackup cannot).
	// The backups are string-sorted by Name(), ascending (ends up
	// being the oldest backup first).
	ListBackups(bucket string) ([]BackupHandle, error)

	// StartBackup creates a new backup with the given name.  If a
	// backup with the same name already exists, it's an error.
	// The returned backup is read-write
	// (AddFile/EndBackup/AbortBackup cann all be called, not
	// ReadFile)
	StartBackup(bucket, name string) (BackupHandle, error)

	// RemoveBackup removes all the data associated with a backup.
	// It will not appear in ListBackups after RemoveBackup succeeds.
	RemoveBackup(bucket, name string) error
}