From a63480a81acdf4b548d5d2673a321c278a018a44 Mon Sep 17 00:00:00 2001
From: Dominic Wong <domwongemail@googlemail.com>
Date: Wed, 1 Jul 2020 15:20:30 +0100
Subject: [PATCH] router/registry: fix fallback fails if service has been seen
 already (#1776)

---
 router/table.go      | 12 +++++++-----
 router/table_test.go | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/router/table.go b/router/table.go
index ad45c725..9508dd4b 100644
--- a/router/table.go
+++ b/router/table.go
@@ -98,6 +98,9 @@ func (t *table) Delete(r Route) error {
 	}
 
 	delete(t.routes[service], sum)
+	if len(t.routes[service]) == 0 {
+		delete(t.routes, service)
+	}
 	if logger.V(logger.DebugLevel, logger.DefaultLogger) {
 		logger.Debugf("Router emitting %s for route: %s", Delete, r.Address)
 	}
@@ -253,8 +256,8 @@ func (t *table) Query(q ...QueryOption) ([]Route, error) {
 
 	if opts.Service != "*" {
 		// try and load services from the cache
-		if _, ok := t.routes[opts.Service]; ok {
-			return findRoutes(t.routes[opts.Service], opts.Address, opts.Gateway, opts.Network, opts.Router, opts.Strategy), nil
+		if routes, ok := t.routes[opts.Service]; ok && len(routes) > 0 {
+			return findRoutes(routes, opts.Address, opts.Gateway, opts.Network, opts.Router, opts.Strategy), nil
 		}
 
 		// load the cache and try again
@@ -263,9 +266,8 @@ func (t *table) Query(q ...QueryOption) ([]Route, error) {
 			return nil, err
 		}
 		t.RLock()
-		if _, ok := t.routes[opts.Service]; ok {
-			return findRoutes(t.routes[opts.Service], opts.Address, opts.Gateway, opts.Network, opts.Router, opts.Strategy), nil
-
+		if routes, ok := t.routes[opts.Service]; ok && len(routes) > 0 {
+			return findRoutes(routes, opts.Address, opts.Gateway, opts.Network, opts.Router, opts.Strategy), nil
 		}
 
 		return nil, ErrRouteNotFound
diff --git a/router/table_test.go b/router/table_test.go
index 8b341123..7c9dd477 100644
--- a/router/table_test.go
+++ b/router/table_test.go
@@ -289,3 +289,44 @@ func TestQuery(t *testing.T) {
 		t.Errorf("incorrect number of routes returned. Expected: %d, found: %d", 1, len(routes))
 	}
 }
+
+func TestFallback(t *testing.T) {
+
+	r := &router{
+		subscribers: make(map[string]chan *Advert),
+		options:     DefaultOptions(),
+	}
+	route := Route{
+		Service: "go.micro.service.foo",
+		Router:  r.options.Id,
+		Link:    DefaultLink,
+		Metric:  DefaultLocalMetric,
+	}
+	r.table = newTable(func(s string) error {
+		r.table.Create(route)
+		return nil
+	})
+	r.start()
+
+	rts, err := r.Lookup(QueryService("go.micro.service.foo"))
+	if err != nil {
+		t.Errorf("error looking up service %s", err)
+	}
+	if len(rts) != 1 {
+		t.Errorf("incorrect number of routes returned %d", len(rts))
+	}
+
+	// deleting from the table but the next query should invoke the fallback that we passed during new table creation
+	if err := r.table.Delete(route); err != nil {
+		t.Errorf("error deleting route %s", err)
+	}
+
+	rts, err = r.Lookup(QueryService("go.micro.service.foo"))
+	if err != nil {
+		t.Errorf("error looking up service %s", err)
+	}
+	if len(rts) != 1 {
+		t.Errorf("incorrect number of routes returned %d", len(rts))
+	}
+
+}