add router selector and network defaults

client/selector/router/router.go

@@ -0,0 +1,153 @@
+// Package router is a network/router selector
+package router
+
+import (
+	"context"
+	"net"
+	"sort"
+	"strconv"
+	"sync"
+
+	"github.com/micro/go-micro/client/selector"
+	"github.com/micro/go-micro/network/router"
+	"github.com/micro/go-micro/registry"
+)
+
+type routerSelector struct {
+	opts selector.Options
+
+	// the router
+	r router.Router
+}
+
+type routerKey struct{}
+
+func (r *routerSelector) Init(opts ...selector.Option) error {
+	// no op
+	return nil
+}
+
+func (r *routerSelector) Options() selector.Options {
+	return r.opts
+}
+
+func (r *routerSelector) Select(service string, opts ...selector.SelectOption) (selector.Next, error) {
+	// lookup router for routes for the service
+	routes, err := r.r.Table().Lookup(router.NewQuery(
+		router.QueryDestination(service),
+	))
+
+	if err != nil {
+		return nil, err
+	}
+
+	// no routes return not found error
+	if len(routes) == 0 {
+		return nil, selector.ErrNotFound
+	}
+
+	// TODO: apply filters by pseudo constructing service
+
+	// sort the routes based on metric
+	sort.Slice(routes, func(i, j int) bool {
+		return routes[i].Metric < routes[j].Metric
+	})
+
+	// roundrobin assuming routes are in metric preference order
+	var i int
+	var mtx sync.Mutex
+
+	return func() (*registry.Node, error) {
+		// get index and increment counter with every call to next
+		mtx.Lock()
+		idx := i
+		i++
+		mtx.Unlock()
+
+		// get route based on idx
+		route := routes[idx%len(routes)]
+
+		// defaults to gateway and no port
+		address := route.Gateway
+		port := 0
+
+		// check if its host:port
+		host, pr, err := net.SplitHostPort(address)
+		if err == nil {
+			pp, _ := strconv.Atoi(pr)
+			// set port
+			port = pp
+			// set address
+			address = host
+		}
+
+		// return as a node
+		return &registry.Node{
+			// TODO: add id and metadata if we can
+			Address: address,
+			Port:    port,
+		}, nil
+	}, nil
+}
+
+func (r *routerSelector) Mark(service string, node *registry.Node, err error) {
+	// TODO: pass back metrics or information to the router
+	return
+}
+
+func (r *routerSelector) Reset(service string) {
+	// TODO: reset the metrics or information at the router
+	return
+}
+
+func (r *routerSelector) Close() error {
+	// stop the router advertisements
+	return r.r.Stop()
+}
+
+func (r *routerSelector) String() string {
+	return "router"
+}
+
+// NewSelector returns a new router based selector
+func NewSelector(opts ...selector.Option) selector.Selector {
+	options := selector.Options{
+		Context: context.Background(),
+	}
+
+	for _, o := range opts {
+		o(&options)
+	}
+
+	// set default registry if not set
+	if options.Registry == nil {
+		options.Registry = registry.DefaultRegistry
+	}
+
+	// try get from the context
+	r, ok := options.Context.Value(routerKey{}).(router.Router)
+	if !ok {
+		// TODO: Use router.DefaultRouter?
+		r = router.NewRouter(
+			router.Registry(options.Registry),
+		)
+	}
+
+	// start the router advertisements
+	r.Advertise()
+
+	return &routerSelector{
+		opts: options,
+		r:    r,
+	}
+}
+
+// WithRouter sets the router as an option
+func WithRouter(r router.Router) selector.Option {
+	return func(o *selector.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, routerKey{}, r)
+	}
+}