relay.go
func (r *relayItems) Entomb(id uint32, deleteAfter time.Duration) (relayItem, bool) {
	r.Lock()
	if r.tombs > _maxRelayTombs {
		r.Unlock()
		r.logger.WithFields(LogField{"id", id}).Warn("Too many tombstones, deleting relay item immediately.")
		return r.Delete(id)
	}
	item, ok := r.items[id]
	if !ok {
		r.Unlock()
		r.logger.WithFields(LogField{"id", id}).Warn("Can't find relay item to entomb.")
		return item, false
	}
	if item.tomb {
		r.Unlock()
		r.logger.WithFields(LogField{"id", id}).Warn("Re-entombing a tombstone.")
		return item, false
	}
	r.tombs++
	item.tomb = true
	r.items[id] = item
	r.Unlock()

	// TODO: We should be clearing these out in batches, rather than creating
	// individual timers for each item.
	time.AfterFunc(deleteAfter, func() { r.Delete(id) })
	return item, true
}
func (r *relayItems) Entomb(id uint32, deleteAfter time.Duration) (relayItem, bool) {
	r.Lock()
	if r.tombs > _maxRelayTombs {
		r.Unlock()
		r.logger.WithFields(LogField{"id", id}).Warn("Too many tombstones, deleting relay item immediately.")
		return r.Delete(id)
	}
	item, ok := r.items[id]
	if !ok {
		r.Unlock()
		r.logger.WithFields(LogField{"id", id}).Warn("Can't find relay item to entomb.")
		return item, false
	}
	if item.tomb {
		r.Unlock()
		r.logger.WithFields(LogField{"id", id}).Warn("Re-entombing a tombstone.")
		return item, false
	}
	r.tombs++
	item.tomb = true
	r.items[id] = item
	r.Unlock()

	// TODO: We should be clearing these out in batches, rather than creating
	// individual timers for each item.
	time.AfterFunc(deleteAfter, func() { r.Delete(id) })
	return item, true
}
// Entomb sets the tomb bit on a relayItem and schedules a garbage collection. It
// returns the entombed item, along with a bool indicating whether we completed
// a relayed call.