lease

type Client interface {
	// Acquire leases `n` resources and returns the lease names.
	// Will block until resources are available or 150m pass, `n` must be > 0.
	// `ctx` can be used to abort the operation, `cancel` is called if any
	// subsequent updates to the lease fail.
	Acquire(rtype string, n uint, ctx context.Context, cancel context.CancelFunc) ([]string, error)
	//AcquireIfAvailableImmediately leases `n` resources and returns the lease names.
	// Does not block, and only leases the resources if they are available right away.
	AcquireIfAvailableImmediately(rtype string, n uint, cancel context.CancelFunc) ([]string, error)
	// Heartbeat updates all leases. It calls the cancellation function of each
	// lease it fails to update.
	Heartbeat() error
	// Release ends one lease by name.
	Release(name string) error
	// ReleaseAll ends all leases and returns the names of those that were
	// successfully released.
	ReleaseAll() ([]string, error)
	// Metrics queries the states of a particular resource, for informational
	// purposes.
	Metrics(rtype string) (Metrics, error)
}

type Metrics struct {
	Free, Leased int
}