源码版本
Kubernetes v1.5.0
go-restful
简介
go-restful是用于构建REST-style web服务的golang包。
它是出现时因为一个javaer在golang中没找到顺手的REST-based服务构建包，所以就按照他在java里常用的JAX-RS的设计，在golang中造了一个轮子。
关键组件
1.Route:
路由包含两种，一种是标准JSR311接口规范的实现RouterJSR311,一种是快速路由CurlyRouter。
CurlyRouter支持正则表达式和动态参数，相比RouterJSR11更加轻量级，apiserver中使用的就是这种路由。
一种Route的设定包含：请求方法(http Method)，请求路径(URL Path),输入输出类型(JSON/YAML)以及对应的回掉函数restful.RouteFunction，响应内容类型(Accept)等。
2.WebService：
WebService逻辑上是Route的集合，功能上主要是为一组Route统一设置包括root path,请求响应的数据类型等一些通用的属性。
需要注意的是，WebService必须加入到Container中才能生效。
func (g *APIGroupVersion) InstallREST(container *restful.Container) error {
installer := g.newInstaller()
ws := installer.NewWebService()
。。。
container.Add(ws)
return utilerrors.NewAggregate(registrationErrors)
}上面是k8s的REST注册接口，也调用了Container.Add(ws)，才能让这个ws生效。
3.Container：
Container逻辑上是WebService的集合，功能上可以实现多终端的效果。
它包括一组restful.WebService和一个http.ServeMux对象，使用RouteSelector进行请求派发。
例如，下面代码中创建了两个Container，分别在不同的port上提供服务。
该代码是go-restful的example：
package main
import (
"github.com/emicklei/go-restful"
"io"
"log"
"net/http"
)
func main() {
ws := new(restful.WebService)
ws.Route(ws.GET("/hello").To(hello))
// ws被添加到默认的container restful.DefaultContainer中
restful.Add(ws)
go func() {
// restful.DefaultContainer监听在端口8080上
http.ListenAndServe(":8080", nil)
}()
container2 := restful.NewContainer()
ws2 := new(restful.WebService)
ws2.Route(ws2.GET("/hello").To(hello2))
// ws2被添加到container2中
container2.Add(ws2)
// container2中监听端口8081
server := &http.Server{Addr: ":8081", Handler: container2}
log.Fatal(server.ListenAndServe())
}
func hello(req *restful.Request, resp *restful.Response) {
io.WriteString(resp, "default world")
}
func hello2(req *restful.Request, resp *restful.Response) {
io.WriteString(resp, "second world")
}4.Filter:
Filter用于动态的拦截请求和响应，类似于放置在相应组件前的钩子，在相应组件功能运行前捕获请求或者响应，主要用于记录log，验证，重定向等功能。
go-restful中有三种类型的Filter：
-
Container Filter:
运行在Container中所有的WebService执行之前。// install a (global) filter for the default container (processed before any webservice) restful.Filter(globalLogging) -
WebService Filter：
运行在WebService中所有的Route执行之前。// install a webservice filter (processed before any route) ws.Filter(webserviceLogging).Filter(measureTime) -
Route Filter:
运行在调用Route绑定的方法之前。// install 2 chained route filters (processed before calling findUser) ws.Route(ws.GET("/{user-id}").Filter(routeLogging).Filter(NewCountFilter().routeCounter).To(findUser))
示例
拿用官方提供的例子：
package main
import (
"github.com/emicklei/go-restful"
"log"
"net/http"
)
type User struct {
Id, Name string
}
type UserResource struct {
// normally one would use DAO (data access object)
users map[string]User
}
func (u UserResource) Register(container *restful.Container) {
// 创建新的WebService
ws := new(restful.WebService)
// 设定WebService对应的路径("/users")和支持的MIME类型(restful.MIME_XML/ restful.MIME_JSON)
ws.
Path("/users").
Consumes(restful.MIME_XML, restful.MIME_JSON).
Produces(restful.MIME_JSON, restful.MIME_XML) // you can specify this per route as well
// 添加路由： GET /{user-id} --> u.findUser
ws.Route(ws.GET("/{user-id}").To(u.findUser))
// 添加路由： POST / --> u.updateUser
ws.Route(ws.POST("").To(u.updateUser))
// 添加路由： PUT /{user-id} --> u.createUser
ws.Route(ws.PUT("/{user-id}").To(u.createUser))
// 添加路由： DELETE /{user-id} --> u.removeUser
ws.Route(ws.DELETE("/{user-id}").To(u.removeUser))
// 将初始化好的WebService添加到Container中
container.Add(ws)
}
// GET http://localhost:8080/users/1
//
func (u UserResource) findUser(request *restful.Request, response *restful.Response) {
id := request.PathParameter("user-id")
usr := u.users[id]
if len(usr.Id) == 0 {
response.AddHeader("Content-Type", "text/plain")
response.WriteErrorString(http.StatusNotFound, "User could not be found.")
} else {
response.WriteEntity(usr)
}
}
// POST http://localhost:8080/users
// 1 Melissa Raspberry 1 Melissa 上面的示例代码构建RESTful服务，分为几个步骤，apiServer也是类似：
1.创建Container
2.配置Container属性：ServeMux/Router type等
3.创建自定义的Resource Handle，实现Resource相关的处理方式。
4.创建对应Resource的WebService，在WebService中添加响应Route，并将WebService加入到Container中。
5.启动监听服务。
apiServer go-restful使用
Container初始化
apiServer的Container相关的结构是APIContainer。
路径：pkg/genericapiserver/mux/container.go
type APIContainer struct {
*restful.Container
NonSwaggerRoutes PathRecorderMux
SecretRoutes Mux
}而该结构是在GenericAPIServer中被使用，分析过apiServer的启动过程的话，应该对该结构比较熟悉。
type GenericAPIServer struct {
discoveryAddresses DiscoveryAddresses
LoopbackClientConfig *restclient.Config
minRequestTimeout time.Duration
...
requestContextMapper api.RequestContextMapper
// 这里使用到了restful.Container
HandlerContainer *genericmux.APIContainer
SecureServingInfo *SecureServingInfo
InsecureServingInfo *ServingInfo
effectiveSecurePort, effectiveInsecurePort int
ExternalAddress string
storage map[string]rest.Storage
Serializer runtime.NegotiatedSerializer
Handler http.Handler
InsecureHandler http.Handler
apiGroupsForDiscoveryLock sync.RWMutex
apiGroupsForDiscovery map[string]unversioned.APIGroup
...
}而该结构的初始化是在master的初始化过程中进行的。
调用过程： main --> App.Run --> master.Complete.New --> c.Config.GenericConfig.SkipComplete().New()
路径： pkg/genericapiserver/config.go
func (c completedConfig) New() (*GenericAPIServer, error) {
if c.Serializer == nil {
return nil, fmt.Errorf("Genericapiserver.New() called with config.Serializer == nil")
}
s := &GenericAPIServer{
discoveryAddresses: c.DiscoveryAddresses,
LoopbackClientConfig: c.LoopbackClientConfig,
legacyAPIGroupPrefixes: c.LegacyAPIGroupPrefixes,
admissionControl: c.AdmissionControl,
requestContextMapper: c.RequestContextMapper,
Serializer: c.Serializer,
minRequestTimeout: time.Duration(c.MinRequestTimeout) * time.Second,
enableSwaggerSupport: c.EnableSwaggerSupport,
SecureServingInfo: c.SecureServingInfo,
InsecureServingInfo: c.InsecureServingInfo,
ExternalAddress: c.ExternalAddress,
apiGroupsForDiscovery: map[string]unversioned.APIGroup{},
enableOpenAPISupport: c.EnableOpenAPISupport,
openAPIConfig: c.OpenAPIConfig,
postStartHooks: map[string]postStartHookEntry{},
}
// 这里进行了Contianer的初始化
s.HandlerContainer = mux.NewAPIContainer(http.NewServeMux(), c.Serializer)
// 添加了DynamicApisDiscovery的
s.installAPI(c.Config)
s.Handler, s.InsecureHandler = c.BuildHandlerChainsFunc(s.HandlerContainer.ServeMux, c.Config)
return s, nil
}继续调用mux.NewAPIContainer()接口创建，该接口的两个参数：新建了一个http的ServeMux; 另一个是实现了编解码序列化反序列化的对象
func NewAPIContainer(mux *http.ServeMux, s runtime.NegotiatedSerializer) *APIContainer {
c := APIContainer{
// New一个Container
Container: restful.NewContainer(),
NonSwaggerRoutes: PathRecorderMux{
mux: mux,
},
SecretRoutes: mux,
}
// 配置http.ServeMux
c.Container.ServeMux = mux
// 配置该Container的路由方式：CurlyRouter 即快速路由
c.Container.Router(restful.CurlyRouter{}) // e.g. for proxy/{kind}/{name}/{*}
// 配置panic产生之后的恢复处理函数
apiserver.InstallRecoverHandler(s, c.Container)
apiserver.InstallServiceErrorHandler(s, c.Container)
return &c
}看下apiserver.InstallRecoverHandler()实现：
func InstallRecoverHandler(s runtime.NegotiatedSerializer, container *restful.Container) {
container.RecoverHandler(func(panicReason interface{}, httpWriter http.ResponseWriter) {
logStackOnRecover(s, panicReason, httpWriter)
})
}
// RecoverHandler changes the default function (logStackOnRecover) to be called
// when a panic is detected. DoNotRecover must be have its default value (=false).
func (c *Container) RecoverHandler(handler RecoverHandleFunction) {
c.recoverHandleFunc = handler
}根据英文注释可以看明白，该RecoverHandler就是在产生panic后会调用的恢复处理函数，默认的调用函数是logStackOnRecover,调用Container.RecoverHandler()后会修改该默认函数，并且Container.DoNotRecover的bool值必须是false才能生效。
apiserver.InstallServiceErrorHandler()接口就不看了，其实就是修改Service Error产生后的错误处理函数，默认是调用writeServiceError()。
到这里Container的初始化基本OK了。
添加WebService
Container已创建并且也进行了初始化。该轮到WebService了，这节会介绍k8s的WebService的创建及添加。
接续上文的Container初始化入口，继续往下看s.installAPI(c.Config):
func (s *GenericAPIServer) installAPI(c *Config) {
// 这里原本还有很多routes.Install()函数
// 这些install()貌似和mux有关。
// 而mux就是一个http的多分器，用于派发某个Request路径到对应的http.Handler进行处理
。。。
// 往HandlerContainer中的Container里添加WebService
// 该WebService的创建在s.DynamicApisDiscovery()中进行
// 实际上创建的WebService是用于list 该group下的所有versions
s.HandlerContainer.Add(s.DynamicApisDiscovery())
}先看下WebService的创建接口s.DynamicApisDiscovery()：
路径：pkg/genericapiserver/genericapiserver.go
// DynamicApisDiscovery returns a webservice serving api group discovery.
// Note: during the server runtime apiGroupsForDiscovery might change.
func (s *GenericAPIServer) DynamicApisDiscovery() *restful.WebService {
return apiserver.NewApisWebService(s.Serializer, APIGroupPrefix, func(req *restful.Request) []unversioned.APIGroup {
// 需要加锁
// 接口注释也有说明。因为k8s可以动态加载第三方apiGroups
s.apiGroupsForDiscoveryLock.RLock()
defer s.apiGroupsForDiscoveryLock.RUnlock()
// 将apiGroupsForDiscovery中所有的APIGroup按照其名字进行升序排序
sortedGroups := []unversioned.APIGroup{}
groupNames := make([]string, 0, len(s.apiGroupsForDiscovery))
for groupName := range s.apiGroupsForDiscovery {
groupNames = append(groupNames, groupName)
}
sort.Strings(groupNames)
for _, groupName := range groupNames {
sortedGroups = append(sortedGroups, s.apiGroupsForDiscovery[groupName])
}
// 创建切片，并填充各个APIGroup的ServerAddressByClientCIDRs信息
clientIP := utilnet.GetClientIP(req.Request)
serverCIDR := s.discoveryAddresses.ServerAddressByClientCIDRs(clientIP)
groups := make([]unversioned.APIGroup, len(sortedGroups))
for i := range sortedGroups {
groups[i] = sortedGroups[i]
groups[i].ServerAddressByClientCIDRs = serverCIDR
}
return groups
})
}继续深入看apiserver.NewApisWebService()，该接口传入了编解码对象，APIGroup的Prefix，还有一个function。
func NewApisWebService(s runtime.NegotiatedSerializer, apiPrefix string, f func(req *restful.Request) []unversioned.APIGroup) *restful.WebService {
// 用于向后兼容v1.1版本，返回一个空的APIGroup
ss := StripVersionNegotiatedSerializer{s}
// 获取支持的媒体类型,比如：application/json，application/yaml
mediaTypes, _ := mediaTypesForSerializer(s)
// 构建go-restful的Route处理方法
rootAPIHandler := RootAPIHandler(ss, f)
// 创建WebService
ws := new(restful.WebService)
// 添加Path
ws.Path(apiPrefix)
// API 说明
ws.Doc("get available API versions")
// 配置GET("/") 转到rootAPIHandler()接口
ws.Route(ws.GET("/").To(rootAPIHandler).
Doc("get available API versions").
Operation("getAPIVersions").
Produces(mediaTypes...).
Consumes(mediaTypes...).
Writes(unversioned.APIGroupList{}))
return ws
}到这里list某个Group下所有的versions的API已经注册完成了。
这些都不是关键的RESTful API的注册，关键的注册都会在pkg/apiserver/apiserver.go中的InstallREST()接口中进行。
琢磨过apiServer启动流程的同学，应该会知道/api和/apis的注册接口最后都会调用到该接口。
/api的注册接口是pkg/genericapiserver/genericapiserver.go中的InstallLegacyAPIGroup()接口
/apis的注册接口是InstallAPIGroup()。
这两个接口都会调用s.installAPIResources()，最后再调用apiGroupVersion.InstallREST()进行API注册。
流程基本就是这样，接着我们直接进入InstallREST()接口看实现：
func (g *APIGroupVersion) InstallREST(container *restful.Container) error {
// 拼装path: "Prefix/Group/Version"
// 然后填充并返回一个APIInstaller对象
installer := g.newInstaller()
// 创建一个WebService
ws := installer.NewWebService()
// 这个是关键，会对各种URL进行注册
apiResources, registrationErrors := installer.Install(ws)
lister := g.ResourceLister
if lister == nil {
lister = staticLister{apiResources}
}
// 增加一个list的API
AddSupportedResourcesWebService(g.Serializer, ws, g.GroupVersion, lister)
// 将该WebService加入到Container
container.Add(ws)
return utilerrors.NewAggregate(registrationErrors)
}前两个调用函数比较简单，这里不进行介绍了。直接进入关键函数installer.Install(ws)：
func (a *APIInstaller) Install(ws *restful.WebService) (apiResources []unversioned.APIResource, errors []error) {
errors = make([]error, 0)
proxyHandler := (&ProxyHandler{
prefix: a.prefix + "/proxy/",
storage: a.group.Storage,
serializer: a.group.Serializer,
mapper: a.group.Context,
})
// 将所有的path合成一个切片，并按照升序重新排序
paths := make([]string, len(a.group.Storage))
var i int = 0
for path := range a.group.Storage {
paths[i] = path
i++
}
sort.Strings(paths)
for _, path := range paths {
// 注册各个URL,关键接口
// 传入的参数：path，rest.Storage，WebService，Handler
apiResource, err := a.registerResourceHandlers(path, a.group.Storage[path], ws, proxyHandler)
if err != nil {
errors = append(errors, fmt.Errorf("error in registering resource: %s, %v", path, err))
}
// 将所有注册成功的Resource合成一个切片
// 将该切片作为返回值，便于之后的接口注册list Resources的API
if apiResource != nil {
apiResources = append(apiResources, *apiResource)
}
}
return apiResources, errors
}该接口先是遍历所有的path，并升序重新排列，然后循环调用接口注册各个URL的API,并将这些注册成功的APIResource加入到同一个切片中。
我们继续看a.registerResourceHandlers()接口：
func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storage, ws *restful.WebService, proxyHandler http.Handler) (*unversioned.APIResource, error) {
...
// 构建creater、lister、deleter、updater、watcher等，其实就是storage
creater, isCreater := storage.(rest.Creater)
namedCreater, isNamedCreater := storage.(rest.NamedCreater)
lister, isLister := storage.(rest.Lister)
getter, isGetter := storage.(rest.Getter)
getterWithOptions, isGetterWithOptions := storage.(rest.GetterWithOptions)
deleter, isDeleter := storage.(rest.Deleter)
gracefulDeleter, isGracefulDeleter := storage.(rest.GracefulDeleter)
collectionDeleter, isCollectionDeleter := storage.(rest.CollectionDeleter)
updater, isUpdater := storage.(rest.Updater)
patcher, isPatcher := storage.(rest.Patcher)
watcher, isWatcher := storage.(rest.Watcher)
_, isRedirector := storage.(rest.Redirector)
connecter, isConnecter := storage.(rest.Connecter)
storageMeta, isMetadata := storage.(rest.StorageMetadata)
...
var apiResource unversioned.APIResource
// k8s资源分为两类：无namespace的RESTScopeNameRoot; 有namespace的RESTScopeNameNamespace
// 在对应的path上添加各类actions，并指定对应的handler。
switch scope.Name() {
case meta.RESTScopeNameRoot:
// Handle non-namespace scoped resources like nodes.
resourcePath := resource
resourceParams := params
itemPath := resourcePath + "/{name}"
nameParams := append(params, nameParam)
proxyParams := append(nameParams, pathParam)
suffix := ""
if hasSubresource {
suffix = "/" + subresource
itemPath = itemPath + suffix
resourcePath = itemPath
resourceParams = nameParams
}
apiResource.Name = path
apiResource.Namespaced = false
apiResource.Kind = resourceKind
namer := rootScopeNaming{scope, a.group.Linker, gpath.Join(a.prefix, resourcePath, "/"), suffix}
// Handler for standard REST verbs (GET, PUT, POST and DELETE).
// Add actions at the resource path: /api/apiVersion/resource
actions = appendIf(actions, action{"LIST", resourcePath, resourceParams, namer, false}, isLister)
actions = appendIf(actions, action{"POST", resourcePath, resourceParams, namer, false}, isCreater)
actions = appendIf(actions, action{"DELETECOLLECTION", resourcePath, resourceParams, namer, false}, isCollectionDeleter)
// DEPRECATED
actions = appendIf(actions, action{"WATCHLIST", "watch/" + resourcePath, resourceParams, namer, false}, allowWatchList)
// Add actions at the item path: /api/apiVersion/resource/{name}
actions = appendIf(actions, action{"GET", itemPath, nameParams, namer, false}, isGetter)
if getSubpath {
actions = appendIf(actions, action{"GET", itemPath + "/{path:*}", proxyParams, namer, false}, isGetter)
}
actions = appendIf(actions, action{"PUT", itemPath, nameParams, namer, false}, isUpdater)
actions = appendIf(actions, action{"PATCH", itemPath, nameParams, namer, false}, isPatcher)
actions = appendIf(actions, action{"DELETE", itemPath, nameParams, namer, false}, isDeleter)
actions = appendIf(actions, action{"WATCH", "watch/" + itemPath, nameParams, namer, false}, isWatcher)
// We add "proxy" subresource to remove the need for the generic top level prefix proxy.
// The generic top level prefix proxy is deprecated in v1.2, and will be removed in 1.3, or 1.4 at the latest.
// TODO: DEPRECATED in v1.2.
actions = appendIf(actions, action{"PROXY", "proxy/" + itemPath + "/{path:*}", proxyParams, namer, false}, isRedirector)
// TODO: DEPRECATED in v1.2.
actions = appendIf(actions, action{"PROXY", "proxy/" + itemPath, nameParams, namer, false}, isRedirector)
actions = appendIf(actions, action{"CONNECT", itemPath, nameParams, namer, false}, isConnecter)
actions = appendIf(actions, action{"CONNECT", itemPath + "/{path:*}", proxyParams, namer, false}, isConnecter && connectSubpath)
break
case meta.RESTScopeNameNamespace:
...
break
default:
return nil, fmt.Errorf("unsupported restscope: %s", scope.Name())
}
...
// 根据之前生成的actions,进行遍历
// 然后在WebService中添加指定的route
for _, action := range actions {
versionedObject := storageMeta.ProducesObject(action.Verb)
if versionedObject == nil {
versionedObject = defaultVersionedObject
}
reqScope.Namer = action.Namer
namespaced := ""
if apiResource.Namespaced {
namespaced = "Namespaced"
}
operationSuffix := ""
if strings.HasSuffix(action.Path, "/{path:*}") {
operationSuffix = operationSuffix + "WithPath"
}
if action.AllNamespaces {
operationSuffix = operationSuffix + "ForAllNamespaces"
namespaced = ""
}
// 判断action的动作类型
// 生成响应的handler，创建route添加到WebService中
switch action.Verb {
case "GET": // Get a resource.
var handler restful.RouteFunction
// 判断是否有参数
if isGetterWithOptions {
handler = GetResourceWithOptions(getterWithOptions, reqScope)
} else {
handler = GetResource(getter, exporter, reqScope)
}
// 生成处理函数
handler = metrics.InstrumentRouteFunc(action.Verb, resource, handler)
doc := "read the specified " + kind
if hasSubresource {
doc = "read " + subresource + " of the specified " + kind
}
route := ws.GET(action.Path).To(handler).
Doc(doc).
Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")).
Operation("read"+namespaced+kind+strings.Title(subresource)+operationSuffix).
Produces(append(storageMeta.ProducesMIMETypes(action.Verb), mediaTypes...)...).
Returns(http.StatusOK, "OK", versionedObject).
Writes(versionedObject)
if isGetterWithOptions {
if err := addObjectParams(ws, route, versionedGetOptions); err != nil {
return nil, err
}
}
if isExporter {
if err := addObjectParams(ws, route, versionedExportOptions); err != nil {
return nil, err
}
}
addParams(route, action.Params)
ws.Route(route)
case "LIST": // List all resources of a kind.
...
case "PUT": // Update a resource.
...
case "PATCH": // Partially update a resource
...
case "POST": // Create a resource.
...
case "DELETE": // Delete a resource.
...
case "DELETECOLLECTION":
...
case "WATCH": // Watch a resource.
...
case "WATCHLIST": // Watch all resources of a kind.
...
case "PROXY": // Proxy requests to a resource.
...
case "CONNECT":
...
}
default:
return nil, fmt.Errorf("unrecognized action verb: %s", action.Verb)
}
// Note: update GetAttribs() when adding a custom handler.
}
return &apiResource, nil
}首先构建creater、lister、getter、deleter、updater、patcher、watcher，其实他们都是storage，只是对应着对etcd的不同操作。
然后针对所有的action，构建响应的handler。创建对应的route,最后把route添加到service里面。这样就完成了api的注册。
关键的REST API注册基本就这样结束了，除此之外还会有很多别的API的注册：
比如APIGroupVersion.InstallREST()接口中的AddSupportedResourcesWebService(g.Serializer, ws, g.GroupVersion, lister)；
GenericAPIServer.InstallLegacyAPIGroup()接口中的apiserver.AddApiWebService()的调用；
等等。。
其实上面也注册了各种REST API，比如像PodList,ServiceList,ReplicationControllerList等。这些就不深入了，都是大同小异。
参考资料
1.go-restful example: http://ernestmicklei.com/2012...
2.go-restful api desgin: http://ernestmicklei.com/2012...
3.go-restful github code： https://github.com/emicklei/g...
4.go-restful GoDoc: https://godoc.org/github.com/...