Add remote lookup via router selector

client/selector/router/router.go

@@ -4,12 +4,15 @@ package router
 import (
 	"context"
 	"net"
+	"os"
 	"sort"
 	"strconv"
 	"sync"
 
+	"github.com/micro/go-micro/client"
 	"github.com/micro/go-micro/client/selector"
 	"github.com/micro/go-micro/network/router"
+	pb "github.com/micro/go-micro/network/router/proto"
 	"github.com/micro/go-micro/registry"
 )
 
@@ -18,10 +21,64 @@ type routerSelector struct {
 
 	// the router
 	r router.Router
+
+	// the client for the remote router
+	c pb.RouterService
+
+	// address of the remote router
+	addr string
+
+	// whether to use the remote router
+	remote bool
 }
 
+type clientKey struct{}
 type routerKey struct{}
 
+// getRoutes returns the routes whether they are remote or local
+func (r *routerSelector) getRoutes(service string) ([]router.Route, error) {
+	if !r.remote {
+		// lookup router for routes for the service
+		return r.r.Table().Lookup(router.NewQuery(
+			router.QueryDestination(service),
+		))
+	}
+
+	// lookup the remote router
+
+	var clientOpts []client.CallOption
+
+	// set the remote address if specified
+	if len(r.addr) > 0 {
+		clientOpts = append(clientOpts, client.WithAddress(r.addr))
+	}
+
+	// call the router
+	pbRoutes, err := r.c.Lookup(context.Background(), &pb.LookupRequest{
+		Query: &pb.Query{
+			Destination: service,
+		},
+	}, clientOpts...)
+	if err != nil {
+		return nil, err
+	}
+
+	var routes []router.Route
+
+	// convert from pb to []*router.Route
+	for _, r := range pbRoutes.Routes {
+		routes = append(routes, router.Route{
+			Destination: r.Destination,
+			Gateway:     r.Gateway,
+			Router:      r.Router,
+			Network:     r.Network,
+			Metric:      int(r.Metric),
+		})
+	}
+
+	return routes, nil
+}
+
 func (r *routerSelector) Init(opts ...selector.Option) error {
 	// no op
 	return nil
@@ -32,11 +89,8 @@ func (r *routerSelector) Options() selector.Options {
 }
 
 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),
-	))
-
+	// TODO: pull routes asynchronously and cache
+	routes, err := r.getRoutes(service)
 	if err != nil {
 		return nil, err
 	}
@@ -124,7 +178,7 @@ func NewSelector(opts ...selector.Option) selector.Selector {
 		options.Registry = registry.DefaultRegistry
 	}
 
-	// try get from the context
+	// try get router from the context
 	r, ok := options.Context.Value(routerKey{}).(router.Router)
 	if !ok {
 		// TODO: Use router.DefaultRouter?
@@ -133,12 +187,43 @@ func NewSelector(opts ...selector.Option) selector.Selector {
 		)
 	}
 
-	// start the router advertisements
-	r.Advertise()
+	// try get client from the context
+	c, ok := options.Context.Value(clientKey{}).(client.Client)
+	if !ok {
+		c = client.DefaultClient
+	}
+
+	// get the router from env vars if its a remote service
+	remote := true
+	routerName := os.Getenv("MICRO_ROUTER")
+	routerAddress := os.Getenv("MICRO_ROUTER_ADDRESS")
+
+	// start the router advertisements if we're running it locally
+	if len(routerName) == 0 && len(routerAddress) == 0 {
+		go r.Advertise()
+		remote = false
+	}
 
 	return &routerSelector{
 		opts: options,
+		// set the internal router
 		r: r,
+		// set the client
+		c: pb.NewRouterService(routerName, c),
+		// address of router
+		addr: routerAddress,
+		// let ourselves know to use the remote router
+		remote: remote,
+	}
+}
+
+// WithClient sets the client for the request
+func WithClient(c client.Client) selector.Option {
+	return func(o *selector.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, clientKey{}, c)
 	}
 }