IPVS sync services performnce improvement (#253)

During periodic sync of IPVS services there is a check if the required service
already existing in IPVS. For the check the list of currnet IPVS services are
read from IPVS. This is causing performance hit as number of services increases.

With this fix, Kube-router reads once from ipvs and use for further during service sync

app/controllers/network_services_controller.go

@@ -238,6 +238,7 @@ type externalIPService struct {
 // as learned from services and endpoints information from the api server
 func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInfoMap, endpointsInfoMap endpointsInfoMap) error {
 
+	var ipvsSvcs []*ipvs.Service
 	start := time.Now()
 	defer func() {
 		glog.Infof("sync ipvs servers took %v", time.Since(start))
@@ -266,6 +267,11 @@ func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInf
 	// map of active services and service endpoints
 	activeServiceEndpointMap := make(map[string][]string)
 
+	ipvsSvcs, err = h.GetServices()
+	if err != nil {
+		return errors.New("Failed get list of IPVS services due to: " + err.Error())
+	}
+
 	for k, svc := range serviceInfoMap {
 		var protocol uint16
 		if svc.protocol == "tcp" {
@@ -283,7 +289,7 @@ func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInf
 		}
 
 		// create IPVS service for the service to be exposed through the cluster ip
-		ipvsClusterVipSvc, err := ipvsAddService(svc.clusterIP, protocol, uint16(svc.port), svc.sessionAffinity, svc.scheduler)
+		ipvsClusterVipSvc, err := ipvsAddService(ipvsSvcs, svc.clusterIP, protocol, uint16(svc.port), svc.sessionAffinity, svc.scheduler)
 		if err != nil {
 			glog.Errorf("Failed to create ipvs service for cluster ip: %s", err.Error())
 			continue
@@ -315,7 +321,7 @@ func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInf
 				nodeServiceIds = make([]string, len(addrs))
 
 				for i, addr := range addrs {
-					ipvsNodeportSvcs[i], err = ipvsAddService(addr.IP, protocol, uint16(svc.nodePort), svc.sessionAffinity, svc.scheduler)
+					ipvsNodeportSvcs[i], err = ipvsAddService(ipvsSvcs, addr.IP, protocol, uint16(svc.nodePort), svc.sessionAffinity, svc.scheduler)
 					if err != nil {
 						glog.Errorf("Failed to create ipvs service for node port due to: %s", err.Error())
 						continue
@@ -326,7 +332,7 @@ func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInf
 				}
 			} else {
 				ipvsNodeportSvcs = make([]*ipvs.Service, 1)
-				ipvsNodeportSvcs[0], err = ipvsAddService(nsc.nodeIP, protocol, uint16(svc.nodePort), svc.sessionAffinity, svc.scheduler)
+				ipvsNodeportSvcs[0], err = ipvsAddService(ipvsSvcs, nsc.nodeIP, protocol, uint16(svc.nodePort), svc.sessionAffinity, svc.scheduler)
 				if err != nil {
 					glog.Errorf("Failed to create ipvs service for node port due to: %s", err.Error())
 					continue
@@ -388,7 +394,7 @@ func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInf
 				}
 
 				// create IPVS service for the service to be exposed through the external ip
-				ipvsExternalIPSvc, err := ipvsAddService(net.ParseIP(externalIP), protocol, uint16(svc.port), svc.sessionAffinity, svc.scheduler)
+				ipvsExternalIPSvc, err := ipvsAddService(ipvsSvcs, net.ParseIP(externalIP), protocol, uint16(svc.port), svc.sessionAffinity, svc.scheduler)
 				if err != nil {
 					glog.Errorf("Failed to create ipvs service for external ip: %s due to %s", externalIP, err.Error())
 					continue
@@ -484,7 +490,8 @@ func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInf
 
 	// cleanup stale ipvs service and servers
 	glog.Infof("Cleaning up if any, old ipvs service and servers which are no longer needed")
-	ipvsSvcs, err := h.GetServices()
+	ipvsSvcs, err = h.GetServices()
+
 	if err != nil {
 		return errors.New("Failed to list IPVS services: " + err.Error())
 	}
@@ -1081,12 +1088,9 @@ func ipvsSetPersistence(svc *ipvs.Service, p bool) {
 	}
 }
 
-func ipvsAddService(vip net.IP, protocol, port uint16, persistent bool, scheduler string) (*ipvs.Service, error) {
-	svcs, err := h.GetServices()
-	if err != nil {
-		return nil, err
-	}
+func ipvsAddService(svcs []*ipvs.Service, vip net.IP, protocol, port uint16, persistent bool, scheduler string) (*ipvs.Service, error) {
 
+	var err error
 	for _, svc := range svcs {
 		if vip.Equal(svc.Address) && protocol == svc.Protocol && port == svc.Port {
 			if (persistent && (svc.Flags&0x0001) == 0) || (!persistent && (svc.Flags&0x0001) != 0) {