// Package lock implements a locking mechanism on shared resources to ensure
// they don't get used at the same time. There needs to be a lock for the following:
// - VM on Host: A VM must only exist on one host at a time
// - Storage attached to VM: Block storage can only be attached to one VM at a time
package lock

// Locker interface used to lock and unlock Lockable resources
type Locker interface {
	Lock(Lockable) error
	Unlock(Lockable) error
}

// Lockable interface must be attached to lockable resources, such as
// Virtual Machines, block devices, and host devices that can be attached
// to virtual machines.
type Lockable interface {
	Locked() bool
	HeldBy() Locker
}