func (ta *TabletActor) executeHook(actionNode *actionnode.ActionNode) (err error) {
	// FIXME(msolomon) shouldn't the reply get distilled into an error?
	h := actionNode.Args.(*hook.Hook)
	topotools.ConfigureTabletHook(h, ta.tabletAlias)
	actionNode.Reply = h.Execute()
	return nil
}

// ExecuteHook executes the provided hook locally, and returns the result.
func (agent *ActionAgent) ExecuteHook(ctx context.Context, hk *hook.Hook) *hook.HookResult {
	if err := agent.lock(ctx); err != nil {
		// client gave up
		return &hook.HookResult{}
	}
	defer agent.unlock()

	// Execute the hooks
	topotools.ConfigureTabletHook(hk, agent.TabletAlias)
	hr := hk.Execute()

	// We never know what the hook did, so let's refresh our state.
	if err := agent.refreshTablet(ctx, "ExecuteHook"); err != nil {
		log.Errorf("refreshTablet after ExecuteHook failed: %v", err)
	}

	return hr
}

// change a tablet type to RESTORE and set all the other arguments.
// from now on, we can go to:
// - back to IDLE if we don't use the tablet at all (after for instance
//   a successful ReserveForRestore but a failed Snapshot)
// - to SCRAP if something in the process on the target host fails
// - to SPARE if the clone works
func (ta *TabletActor) changeTypeToRestore(tablet, sourceTablet *topo.TabletInfo, parentAlias topo.TabletAlias, keyRange key.KeyRange) error {
	// run the optional preflight_assigned hook
	hk := hook.NewSimpleHook("preflight_assigned")
	topotools.ConfigureTabletHook(hk, ta.tabletAlias)
	if err := hk.ExecuteOptional(); err != nil {
		return err
	}

	// change the type
	tablet.Parent = parentAlias
	tablet.Keyspace = sourceTablet.Keyspace
	tablet.Shard = sourceTablet.Shard
	tablet.Type = topo.TYPE_RESTORE
	tablet.KeyRange = keyRange
	tablet.DbNameOverride = sourceTablet.DbNameOverride
	if err := topo.UpdateTablet(ta.ts, tablet); err != nil {
		return err
	}

	// and create the replication graph items
	return topo.CreateTabletReplicationData(ta.ts, tablet.Tablet)
}

// ExecuteHook executes the provided hook locally, and returns the result.
// Should be called under RPCWrapLockAction.
func (agent *ActionAgent) ExecuteHook(ctx context.Context, hk *hook.Hook) *hook.HookResult {
	topotools.ConfigureTabletHook(hk, agent.TabletAlias)
	return hk.Execute()
}