kubelet分析-csi driver注册分析-Node Driver Registrar源码分析
Node Driver Registrar分析
node-driver-registrar是一个sidecar容器，通过Kubelet的插件注册机制将CSI plugin（csi driver，两个名词意义一样）注册到Kubelet，让kubelet做volume的mount/umount操作时知道怎么调用相应的csi plugin。
Node Driver Registrar的内容相对简单，将在本文中对其作用、源码、组件间调用逻辑等进行分析。
repo：https://github.com/kubernetes-csi/node-driver-registrar
关联博客
Node Driver Registrar启动参数
// cmd/csi-node-driver-registrar/main.go
// Command line flags
var (
connectionTimeout = flag.Duration("connection-timeout", 0, "The --connection-timeout flag is deprecated")
csiAddress = flag.String("csi-address", "/run/csi/socket", "Path of the CSI driver socket that the node-driver-registrar will connect to.")
kubeletRegistrationPath = flag.String("kubelet-registration-path", "", "Path of the CSI driver socket on the Kubernetes host machine.")
showVersion = flag.Bool("version", false, "Show version.")
version = "unknown"
// List of supported versions
supportedVersions = []string{"1.0.0"}
)
下面讲解下最关键的两个启动参数，主要是配置2个socket地址。
（1）csi-address
csi plugin组件暴露的grpc服务socket地址。
（2）kubelet-registration-path
Node Driver Registrar容器暴露的grpc服务socket地址，同时kubelet也会通过该socket地址访问Node Driver Registrar容器的接口，主要用于向kubelet注册csi plugin。
Node Driver Registrar容器权限
（1）RBAC：Node Driver Registrar容器没有访问kubernetes API的需求，所以不用做相关的RBAC配置。
（2）需要将前面提到的2个socket的父目录作为hostPath挂载进容器中，并对socket拥有创建、删除、访问等权限（通过配置containers[].securityContext.privileged=true获得权限）。
Node Driver Registrar容器部署yaml
Node-Driver-Registrar容器与csi plugin NodeServer容器一起，使用daemonset部署，即每个node节点都有。
Node-Driver-Registrar容器的部署yaml如下：
containers:
- name: driver-registrar-rbd
# This is necessary only for systems with SELinux, where
# non-privileged sidecar containers cannot access unix domain socket
# created by privileged CSI driver container.
securityContext:
privileged: true
image: quay.io/k8scsi/csi/csi-node-driver-registrar:v1.3.0
args:
- "--v=5"
- "--csi-address=/csi/csi.sock"
- "--kubelet-registration-path=/var/lib/kubelet/plugins/rbd.csi.ceph.com/csi.sock"
lifecycle:
preStop:
exec:
command: [
"/bin/sh", "-c",
"rm -rf /registration/rbd.csi.ceph.com \
/registration/rbd.csi.ceph.com-reg.sock"
]
env:
- name: KUBE_NODE_NAME
valueFrom:
fieldRef:
fieldPath: spec.nodeName
volumeMounts:
- name: socket-dir
mountPath: /csi
- name: registration-dir
mountPath: /registration
imagePullPolicy: "Always"
volumes:
- name: socket-dir
hostPath:
path: /var/lib/kubelet/plugins/rbd.csi.ceph.com
type: DirectoryOrCreate
- name: registration-dir
hostPath:
path: /var/lib/kubelet/plugins_registry/
type: Directory
Node Driver Registrar注册csi plugin driver步骤
第 1 步
Node Driver Registrar连接csi plugin组件暴露的grpc服务socket地址，调用GetPluginInfo接口，获取csi plugin的driver名称。
第 2 步
在 kubelet-registration-path目录下启动一个 socket，对外暴露GetInfo 和 NotifyRegistrationStatus 两个接口。kubelet 通过 Watcher可以发现该socket。
第 3 步
kubelet 通过 Watcher监控/var/lib/kubelet/plugins_registry/目录，发现上述socket 后，通过该 socket 调用 Node-Driver-Registrar 的 GetInfo 接口，获取csi plugin组件暴露的grpc服务socket地址以及csi plugin组件的driver名称。
第 4 步
kubelet 通过csi plugin组件暴露的grpc服务socket地址对其NodeGetInfo接口进行调用，获取csi plugin的nodeID等信息。
第 5 步
kubelet根据上一步获得的信息，去更新node节点的 Annotations、Labels、status.allocatable 等信息，同时创建（或更新）一个 CSINode 对象。
第 6 步
kubelet通过socket调用Node-Driver-Registrar容器的NotifyRegistrationStatus接口，通知注册csi plugin成功。
通过以上 6 步就实现了 csi plugin注册机制。
Node Driver Registrar源码分析
下面结合Node Driver Registrar的源码对注册csi plugin driver步骤进行详细分析。主要分析main()、nodeRegister()、GetInfo()与NotifyRegistrationStatus()。
1.main()
先从main()入手。
主要逻辑：
（1）组件启动参数校验；
（2）连接csi plugin组件暴露的grpc服务socket地址，调用GetPluginInfo接口，获取csi plugin的driver名称；
（3）调用nodeRegister方法做csi plugin注册操作。
// cmd/csi-node-driver-registrar/main.go
func main() {
klog.InitFlags(nil)
flag.Set("logtostderr", "true")
flag.Parse()
if *kubeletRegistrationPath == "" {
klog.Error("kubelet-registration-path is a required parameter")
os.Exit(1)
}
if *showVersion {
fmt.Println(os.Args[0], version)
return
}
klog.Infof("Version: %s", version)
if *connectionTimeout != 0 {
klog.Warning("--connection-timeout is deprecated and will have no effect")
}
// Once https://github.com/container-storage-interface/spec/issues/159 is
// resolved, if plugin does not support PUBLISH_UNPUBLISH_VOLUME, then we
// can skip adding mapping to "csi.volume.kubernetes.io/nodeid" annotation.
klog.V(1).Infof("Attempting to open a gRPC connection with: %q", *csiAddress)
csiConn, err := connection.Connect(*csiAddress)
if err != nil {
klog.Errorf("error connecting to CSI driver: %v", err)
os.Exit(1)
}
klog.V(1).Infof("Calling CSI driver to discover driver name")
ctx, cancel := context.WithTimeout(context.Background(), csiTimeout)
defer cancel()
csiDriverName, err := csirpc.GetDriverName(ctx, csiConn)
if err != nil {
klog.Errorf("error retreiving CSI driver name: %v", err)
os.Exit(1)
}
klog.V(2).Infof("CSI driver name: %q", csiDriverName)
// Run forever
nodeRegister(csiDriverName)
}
2.nodeRegister()
nodeRegister()用于向kubelet注册csi plugin。主要逻辑：
（1）调用newRegistrationServer()初始化registrationServer结构体；
（2）在 kubelet-registration-path目录下启动一个 socket，对外暴露GetInfo 和 NotifyRegistrationStatus 两个接口（kubelet 通过 Watcher可以发现该socket）。
// cmd/csi-node-driver-registrar/node_register.go
func nodeRegister(
csiDriverName string,
) {
// When kubeletRegistrationPath is specified then driver-registrar ONLY acts
// as gRPC server which replies to registration requests initiated by kubelet's
// pluginswatcher infrastructure. Node labeling is done by kubelet's csi code.
registrar := newRegistrationServer(csiDriverName, *kubeletRegistrationPath, supportedVersions)
socketPath := fmt.Sprintf("/registration/%s-reg.sock", csiDriverName)
if err := util.CleanupSocketFile(socketPath); err != nil {
klog.Errorf("%+v", err)
os.Exit(1)
}
var oldmask int
if runtime.GOOS == "linux" {
// Default to only user accessible socket, caller can open up later if desired
oldmask, _ = util.Umask(0077)
}
klog.Infof("Starting Registration Server at: %s\n", socketPath)
lis, err := net.Listen("unix", socketPath)
if err != nil {
klog.Errorf("failed to listen on socket: %s with error: %+v", socketPath, err)
os.Exit(1)
}
if runtime.GOOS == "linux" {
util.Umask(oldmask)
}
klog.Infof("Registration Server started at: %s\n", socketPath)
grpcServer := grpc.NewServer()
// Registers kubelet plugin watcher api.
registerapi.RegisterRegistrationServer(grpcServer, registrar)
// Starts service
if err := grpcServer.Serve(lis); err != nil {
klog.Errorf("Registration Server stopped serving: %v", err)
os.Exit(1)
}
// If gRPC server is gracefully shutdown, exit
os.Exit(0)
}
newRegistrationServer()
// cmd/csi-node-driver-registrar/main.go
// NewregistrationServer returns an initialized registrationServer instance
func newRegistrationServer(driverName string, endpoint string, versions []string) registerapi.RegistrationServer {
return ®istrationServer{
driverName: driverName,
endpoint: endpoint,
version: versions,
}
}
3.GetInfo()
GetInfo()：kubelet 通过调用 Node-Driver-Registrar 的 GetInfo 接口，获取csi plugin组件暴露的grpc服务socket地址以及csi plugin组件的driver名称。
// GetInfo is the RPC invoked by plugin watcher
func (e registrationServer) GetInfo(ctx context.Context, req *registerapi.InfoRequest) (*registerapi.PluginInfo, error) {
klog.Infof("Received GetInfo call: %+v", req)
return ®isterapi.PluginInfo{
Type: registerapi.CSIPlugin,
Name: e.driverName,
Endpoint: e.endpoint,
SupportedVersions: e.version,
}, nil
}
4.NotifyRegistrationStatus()
NotifyRegistrationStatus()：kubelet通过调用Node-Driver-Registrar的NotifyRegistrationStatus接口，通知注册csi plugin成功。
// GetInfo is the RPC invoked by plugin watcher
func (e registrationServer) NotifyRegistrationStatus(ctx context.Context, status *registerapi.RegistrationStatus) (*registerapi.RegistrationStatusResponse, error) {
klog.Infof("Received NotifyRegistrationStatus call: %+v", status)
if !status.PluginRegistered {
klog.Errorf("Registration process failed with error: %+v, restarting registration container.", status.Error)
os.Exit(1)
}
return ®isterapi.RegistrationStatusResponse{}, nil
}
总结
Node Driver Registrar作用
Node Driver Registrar涉及的两个socket
（1）csi-address
csi plugin组件暴露的grpc服务socket地址。
（2）kubelet-registration-path
Node Driver Registrar容器暴露的grpc服务socket地址，同时kubelet也会通过该socket地址访问Node Driver Registrar容器的接口，主要用于向kubelet注册csi plugin。
关于cluster-driver-registrar
旧的注册组件driver-registrar已被cluster-driver-registrar与node-driver-registrar两个组件替代，其中cluster-driver-registrar也已经deprecated。
注册组件可分为cluster-driver-registrar与node-driver-registrar，两者的作用不同，自动/手工创建CSIDriver object替代了cluster-driver-registrar组件的作用，node-driver-registrar任然需要，具体作用可以参考下方组件的readme链接。
driver-registrar：https://github.com/kubernetes-csi/driver-registrar#readme
cluster-driver-registrar：https://github.com/kubernetes-csi/cluster-driver-registrar#readme
node-driver-registrar：https://github.com/kubernetes-csi/node-driver-registrar#readme
