add service interface

As services in KubeVirt grow, it's useful to standardize the interface
each service has to implement. This leads to more unified
implementation of things such as flag handling.

This is accomplished by creating `service.Service` interface and
compile-check that each service conforms to this interface.

Signed-off-by: Martin Polednik <[email protected]>

cmd/virt-handler/virt-handler.go

@@ -59,14 +59,16 @@ import (
 const defaultWatchdogTimeout = 30 * time.Second
 
 type virtHandlerApp struct {
-	Service                 *service.Service
+	Service                 *service.ServiceListen
 	HostOverride            string
 	LibvirtUri              string
 	VirtShareDir            string
 	EphemeralDiskDir        string
 	WatchdogTimeoutDuration time.Duration
 }
 
+var _ service.Service = &virtHandlerApp{}
+
 func newVirtHandlerApp(host *string, port *int, hostOverride *string, libvirtUri *string, virtShareDir *string, ephemeralDiskDir *string, watchdogTimeoutDuration *time.Duration) *virtHandlerApp {
 	if *hostOverride == "" {
 		defaultHostName, err := os.Hostname()
@@ -77,7 +79,7 @@ func newVirtHandlerApp(host *string, port *int, hostOverride *string, libvirtUri
 	}
 
 	return &virtHandlerApp{
-		Service:                 service.NewService("virt-handler", *host, *port),
+		Service:                 service.NewServiceListen("virt-handler", host, port),
 		HostOverride:            *hostOverride,
 		LibvirtUri:              *libvirtUri,
 		VirtShareDir:            *virtShareDir,

cmd/virt-manifest/virt-manifest.go

@@ -35,17 +35,19 @@ import (
 )
 
 type virtManifestApp struct {
-	Service    *service.Service
+	Service    *service.ServiceListen
 	LibvirtUri string
 }
 
 func newVirtManifestApp(host *string, port *int, libvirtUri *string) *virtManifestApp {
 	return &virtManifestApp{
-		Service:    service.NewService("virt-manifest", *host, *port),
+		Service:    service.NewServiceListen("virt-manifest", host, port),
 		LibvirtUri: *libvirtUri,
 	}
 }
 
+var _ service.Service = &virtManifestApp{}
+
 func (app *virtManifestApp) Run() {
 	logger := log.Log
 	logger.Info("Starting virt-manifest server")

pkg/service/service.go

@@ -24,20 +24,24 @@ import (
 	"strconv"
 )
 
-type Service struct {
+type Service interface {
+	Run()
+}
+
+type ServiceListen struct {
 	Name string
 	Host string
 	Port string
 }
 
-func NewService(name string, host string, port int) *Service {
-	return &Service{
+func NewServiceListen(name string, host *string, port *int) *ServiceListen {
+	return &ServiceListen{
 		Name: name,
 		Host: host,
 		Port: strconv.Itoa(port),
 	}
 }
 
-func (service *Service) Address() string {
+func (service *ServiceListen) Address() string {
 	return fmt.Sprintf("%s:%s", service.Host, service.Port)
 }

pkg/virt-api/api.go

@@ -22,17 +22,19 @@ import (
 )
 
 type virtAPIApp struct {
-	Service   *service.Service
+	Service   *service.ServiceListen
 	SwaggerUI string
 }
 
 func NewVirtAPIApp(host string, port int, swaggerUI string) *virtAPIApp {
 	return &virtAPIApp{
-		Service:   service.NewService("virt-api", host, port),
+		Service:   service.NewServiceListen("virt-api", host, port),
 		SwaggerUI: swaggerUI,
 	}
 }
 
+var _ service.Service = &virtAPIApp{}
+
 func (app *virtAPIApp) Compose() {
 	ctx := context.Background()
 	vmGVR := schema.GroupVersionResource{Group: v1.GroupVersion.Group, Version: v1.GroupVersion.Version, Resource: "virtualmachines"}

pkg/virt-controller/watch/application.go

@@ -22,6 +22,7 @@ import (
 	"kubevirt.io/kubevirt/pkg/kubecli"
 	"kubevirt.io/kubevirt/pkg/log"
 	"kubevirt.io/kubevirt/pkg/registry-disk"
+	"kubevirt.io/kubevirt/pkg/service"
 	"kubevirt.io/kubevirt/pkg/virt-controller/leaderelectionconfig"
 	"kubevirt.io/kubevirt/pkg/virt-controller/rest"
 	"kubevirt.io/kubevirt/pkg/virt-controller/services"
@@ -60,6 +61,8 @@ type VirtControllerApp struct {
 	readyChan        chan bool
 }
 
+var _ service.Service = &VirtControllerApp{}
+
 func Execute() {
 	var err error
 	var app VirtControllerApp = VirtControllerApp{}