Update simple_grain_pool.go

pkg/actor/simple_grain_pool.go

@@ -144,8 +144,17 @@ func (p *SimpleGrainPool[V]) TakeOwnership(id uint64) {
 }
 
 func (p *SimpleGrainPool[V]) AddRemote(host string) (Host, error) {
-	if host == "" || host == p.hostname || p.IsKnown(host) {
-		return nil, fmt.Errorf("invalid host")
+	if host == "" {
+		return nil, fmt.Errorf("host is empty")
+	}
+	if host == p.hostname {
+		return nil, fmt.Errorf("same host, this should not happen")
+	}
+	p.remoteMu.RLock()
+	existing, found := p.remoteHosts[host]
+	p.remoteMu.RUnlock()
+	if found {
+		return existing, nil
 	}
 
 	remote, err := p.spawnHost(host)