selector

Overview ¶

The Selector package provides a way to algorithmically filter and return nodes required by the client or any other system. Selector's implemented by Micro build on the registry but it's of optional use. One could provide a static Selector that has a fixed pool.

func (r *randomSelector) Select(service string, opts ...SelectOption) (Next, error) {
	var sopts SelectOptions
	for _, opt := range opts {
		opt(&sopts)
	}

	// get the service
	services, err := r.so.Registry.GetService(service)
	if err != nil {
		return nil, err
	}

	// apply the filters
	for _, filter := range sopts.Filters {
		services = filter(services)
	}

	// if there's nothing left, return
	if len(services) == 0 {
		return nil, ErrNotFound
	}

	var nodes []*registry.Node

	for _, service := range services {
		for _, node := range service.Nodes {
			nodes = append(nodes, node)
		}
	}

	if len(nodes) == 0 {
		return nil, ErrNotFound
	}

	return func() (*registry.Node, error) {
		i := rand.Int()
		j := i % len(services)

		if len(services[j].Nodes) == 0 {
			return nil, ErrNotFound
		}

		k := i % len(services[j].Nodes)
		return services[j].Nodes[k], nil
	}, nil
}