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REST(Representational State Transfer,表现层状态转化)是近几年使用较广泛的分布式结点间同步通信的实现方式。REST原则描述网络中client-server的一种交互形式,即用URL定位资源,用HTTP方法描述操作的交互形式。如果CS之间交互的网络接口满足REST风格,则称为RESTful API。以下是 理解RESTful架构 总结的REST原则:
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为什么要设计RESTful的API,个人理解原因在于:用HTTP的操作统一数据操作接口,限制URL为资源,即每次请求对应某种资源的某种操作,这种 无状态的设计可以实现client-server的解耦分离,保证系统两端都有横向扩展能力。
go-restful
go-restful is a package for building REST-style Web Services using Google Go。go-restful定义了Container WebService和Route三个重要数据结构。
最简单的使用实例,向WebService注册路由,将WebService添加到Container中,由Container负责分发。
func main() { ws := new(restful.WebService) ws.Path("/users") ws.Route(ws.GET("/").To(u.findAllUsers). Doc("get all users"). Metadata(restfulspec.KeyOpenAPITags, tags). Writes([]User{}). Returns(200, "OK", []User{})) container := restful.NewContainer().Add(ws) http.ListenAndServe(":8080", container) }
container
container是根据标准库http的路由器ServeMux写的,并且它通过ServeMux的路由表实现了Handler接口,可参考以前的这篇 HTTP协议与Go的实现 。
type Container struct { webServicesLock sync.RWMutex webServices []*WebService ServeMux *http.ServeMux isRegisteredOnRoot bool containerFilters []FilterFunction doNotRecover bool // default is true recoverHandleFunc RecoverHandleFunction serviceErrorHandleFunc ServiceErrorHandleFunction router RouteSelector // default is a CurlyRouter contentEncodingEnabled bool // default is false }
func (c *Container)ServeHTTP(httpwriter http.ResponseWriter, httpRequest *http.Request) { c.ServeMux.ServeHTTP(httpwriter, httpRequest) }
往Container内添加WebService,内部维护的webServices不能有重复的RootPath,
func (c *Container)Add(service *WebService)*Container { c.webServicesLock.Lock() defer c.webServicesLock.Unlock() if !c.isRegisteredOnRoot { c.isRegisteredOnRoot = c.addHandler(service, c.ServeMux) } c.webServices = append(c.webServices, service) return c }
添加到container并注册到mux的是dispatch这个函数,它负责根据不同WebService的rootPath进行分发。
func (c *Container)addHandler(service *WebService, serveMux *http.ServeMux)bool { pattern := fixedPrefixPath(service.RootPath()) serveMux.HandleFunc(pattern, c.dispatch) }
webservice
每组webservice表示一个共享rootPath的服务,其中rootPath通过 ws.Path() 设置。
type WebService struct { rootPath string pathExpr *pathExpression routes []Route produces []string consumes []string pathParameters []*Parameter filters []FilterFunction documentation string apiVersion string typeNameHandleFunc TypeNameHandleFunction dynamicRoutes bool routesLock sync.RWMutex }
通过Route注册的路由最终构成Route结构体,添加到WebService的routes中。
func (w *WebService)Route(builder *RouteBuilder)*WebService { w.routesLock.Lock() defer w.routesLock.Unlock() builder.copyDefaults(w.produces, w.consumes) w.routes = append(w.routes, builder.Build()) return w }
route
通过RouteBuilder构造Route信息,Path结合了rootPath和subPath。Function是路由Handler,即处理函数,它通过 ws.Get(subPath).To(function) 的方式加入。Filters实现了个类似gRPC拦截器的东西,也类似go-chassis的chain。
type Route struct { Method string Produces []string Consumes []string Path string // webservice root path + described path Function RouteFunction Filters []FilterFunction If []RouteSelectionConditionFunction // cached values for dispatching relativePath string pathParts []string pathExpr *pathExpression // documentation Doc string Notes string Operation string ParameterDocs []*Parameter ResponseErrors map[int]ResponseError ReadSample, WriteSample interface{} Metadata map[string]interface{} Deprecated bool }
dispatch
server侧的主要功能就是路由选择和分发。http包实现了一个 ServeMux ,go-restful在这个基础上封装了多个服务,如何在从container开始将路由分发给webservice,再由webservice分发给具体处理函数。这些都在 dispatch 中实现。
func (c *Container)dispatch(httpWriter http.ResponseWriter, httpRequest *http.Request) { func() { c.webServicesLock.RLock() defer c.webServicesLock.RUnlock() webService, route, err = c.router.SelectRoute( c.webServices, httpRequest) }() pathProcessor, routerProcessesPath := c.router.(PathProcessor) pathParams := pathProcessor.ExtractParameters(route, webService, httpRequest.URL.Path) wrappedRequest, wrappedResponse := route.wrapRequestResponse(writer, httpRequest, pathParams) if len(c.containerFilters)+len(webService.filters)+len(route.Filters) > 0 { chain := FilterChain{Filters: allFilters, Target: func(req *Request, resp *Response) { // handle request by route after passing all filters route.Function(wrappedRequest, wrappedResponse) }} chain.ProcessFilter(wrappedRequest, wrappedResponse) } else { route.Function(wrappedRequest, wrappedResponse) } }
go-chassis
go-chassis实现的rest-server是在go-restful上的一层封装。Register时只要将注册的schema解析成routes,并注册到webService中,Start启动server时 container.Add(r.ws) ,同时将container作为handler交给 http.Server , 最后开始ListenAndServe即可。
type restfulServer struct { microServiceName string container *restful.Container ws *restful.WebService opts server.Options mux sync.RWMutex exit chan chan error server *http.Server }
根据Method不同,向WebService注册不同方法的handle,从schema读取的routes信息包含Method,Func以及PathPattern。
func (r *restfulServer)Register(schemainterface{}, options ...server.RegisterOption)(string, error) { schemaType := reflect.TypeOf(schema) schemaValue := reflect.ValueOf(schema) var schemaName string tokens := strings.Split(schemaType.String(), ".") if len(tokens) >= 1 { schemaName = tokens[len(tokens)-1] } routes, err := GetRoutes(schema) for _, route := range routes { lager.Logger.Infof("Add route path: [%s] Method: [%s] Func: [%s]. ", route.Path, route.Method, route.ResourceFuncName) method, exist := schemaType.MethodByName(route.ResourceFuncName) ... handle := func(req *restful.Request, rep *restful.Response) { c, err := handler.GetChain(common.Provider, r.opts.ChainName) inv := invocation.Invocation{ MicroServiceName: config.SelfServiceName, SourceMicroService: req.HeaderParameter(common.HeaderSourceName), Args: req, Protocol: common.ProtocolRest, SchemaID: schemaName, OperationID: method.Name, } bs := NewBaseServer(context.TODO()) bs.req = req bs.resp = rep c.Next(&inv, func(ir *invocation.InvocationResponse)error { if ir.Err != nil { return ir.Err } method.Func.Call([]reflect.Value{schemaValue, reflect.ValueOf(bs)}) if bs.resp.StatusCode() >= http.StatusBadRequest { return ... } return nil }) } switch route.Method { case http.MethodGet: r.ws.Route(r.ws.GET(route.Path).To(handle). Doc(route.ResourceFuncName). Operation(route.ResourceFuncName)) ... } } return reflect.TypeOf(schema).String(), nil }
实在是比较简单,就不写了。今天好困。
遗留问题
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