router/registry: fix rlock bug when registry errors (#1788)

* client: add select options

* router/registry: fix rlock bug when registry errors

* Revert "client: add select options"

This reverts commit 4d5283452e183f7387b604b51bde1deaf87ee391.

* router/registry: findRoutes under rlock

* add test

Co-authored-by: Dominic Wong <dom@micro.mu>

router/table.go

@@ -240,9 +240,6 @@ func findRoutes(routes map[uint64]Route, address, gateway, network, router strin
 
 // Lookup queries routing table and returns all routes that match the lookup query
 func (t *table) Query(q ...QueryOption) ([]Route, error) {
-	t.RLock()
-	defer t.RUnlock()
-
 	// create new query options
 	opts := NewQuery(q...)
 
@@ -254,29 +251,44 @@ func (t *table) Query(q ...QueryOption) ([]Route, error) {
 		return results, nil
 	}
 
+	// readAndFilter routes for this service under read lock.
+	readAndFilter := func() ([]Route, bool) {
+		t.RLock()
+		defer t.RUnlock()
+
+		routes, ok := t.routes[opts.Service]
+		if !ok || len(routes) == 0 {
+			return nil, false
+		}
+
+		return findRoutes(routes, opts.Address, opts.Gateway, opts.Network, opts.Router, opts.Strategy), true
+	}
+
 	if opts.Service != "*" {
 		// try and load services from the cache
-		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
+		if routes, ok := readAndFilter(); ok {
+			return routes, nil
 		}
 
 		// load the cache and try again
-		t.RUnlock()
 		if err := t.fetchRoutes(opts.Service); err != nil {
 			return nil, err
 		}
-		t.RLock()
-		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
+
+		// try again
+		if routes, ok := readAndFilter(); ok {
+			return routes, nil
 		}
 
 		return nil, ErrRouteNotFound
 	}
 
 	// search through all destinations
+	t.RLock()
 	for _, routes := range t.routes {
 		results = append(results, findRoutes(routes, opts.Address, opts.Gateway, opts.Network, opts.Router, opts.Strategy)...)
 	}
+	t.RUnlock()
 
 	return results, nil
 }

router/table_test.go

@@ -330,3 +330,19 @@ func TestFallback(t *testing.T) {
 	}
 
 }
+
+func TestFallbackError(t *testing.T) {
+	r := &router{
+		subscribers: make(map[string]chan *Advert),
+		options:     DefaultOptions(),
+	}
+	r.table = newTable(func(s string) error {
+		return fmt.Errorf("ERROR")
+	})
+	r.start()
+	_, err := r.Lookup(QueryService("go.micro.service.foo"))
+	if err == nil {
+		t.Errorf("expected error looking up service but none returned")
+	}
+
+}