Docker Swarm代码分析笔记(8)——创建Docker API router

......
server.SetHandler(api.NewPrimary(cl, tlsConfig, &statusHandler{cl, nil, nil}, c.GlobalBool("debug"), c.Bool("cors")))
......

api.Server结构体定义如下:

// Server is a Docker API server.
type Server struct {
 hosts []string
 tlsConfig *tls.Config
 dispatcher *dispatcher
}

其中处理HTTP请求的相关方法如下:

// Dispatcher is a meta http.Handler. It acts as an http.Handler and forwards
// requests to another http.Handler that can be changed at runtime.
type dispatcher struct {
 handler http.Handler
}
// SetHandler changes the underlying handler.
func (d *dispatcher) SetHandler(handler http.Handler) {
 d.handler = handler
}
// ServeHTTP forwards requests to the underlying handler.
func (d *dispatcher) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 if d.handler == nil {
 httpError(w, "No dispatcher defined", http.StatusInternalServerError)
 return
 }
 d.handler.ServeHTTP(w, r)
}
// SetHandler is used to overwrite the HTTP handler for the API.
// This can be the api router or a reverse proxy.
func (s *Server) SetHandler(handler http.Handler) {
 s.dispatcher.SetHandler(handler)
}

Server.SetHandler所做的就是把handler赋给Server.dispatcher.handler。handler类型是http.Handler:

type Handler interface {
 ServeHTTP(ResponseWriter, *Request)
}

api.NewPrimary利用了mux这个project:

// NewPrimary creates a new API router.
func NewPrimary(cluster cluster.Cluster, tlsConfig *tls.Config, status StatusHandler, debug, enableCors bool) *mux.Router {
 // Register the API events handler in the cluster.
 eventsHandler := newEventsHandler()
 cluster.RegisterEventHandler(eventsHandler)
 context := &context{
 cluster: cluster,
 eventsHandler: eventsHandler,
 statusHandler: status,
 tlsConfig: tlsConfig,
 }
 r := mux.NewRouter()
 setupPrimaryRouter(r, context, enableCors)
 if debug {
 profilerSetup(r, "/debug/")
 }
 return r
}

而*mux.Router实现了ServeHTTP这个方法,所以符合http.Handler这个interface:

// ServeHTTP dispatches the handler registered in the matched route.
//
// When there is a match, the route variables can be retrieved calling
// mux.Vars(request).
func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 ......
}

api.Server的ListenAndServe()函数定义了新的http.Server变量,利用上面实现的api.Server.dispatcher的ServeHTTP方法来响应HTTP请求:

server = &http.Server{
 Addr: protoAddrParts[1],
 Handler: s.dispatcher,
 }

func setupPrimaryRouter(r *mux.Router, context *context, enableCors bool) {
 for method, mappings := range routes {
 for route, fct := range mappings {
 log.WithFields(log.Fields{"method": method, "route": route}).Debug("Registering HTTP route")
 localRoute := route
 localFct := fct
 wrap := func(w http.ResponseWriter, r *http.Request) {
 log.WithFields(log.Fields{"method": r.Method, "uri": r.RequestURI}).Debug("HTTP request received")
 if enableCors {
 writeCorsHeaders(w, r)
 }
 context.apiVersion = mux.Vars(r)["version"]
 localFct(context, w, r)
 }
 localMethod := method
 r.Path("/v{version:[0-9]+.[0-9]+}" + localRoute).Methods(localMethod).HandlerFunc(wrap)
 r.Path(localRoute).Methods(localMethod).HandlerFunc(wrap)
 if enableCors {
 optionsMethod := "OPTIONS"
 optionsFct := optionsHandler
 wrap := func(w http.ResponseWriter, r *http.Request) {
 log.WithFields(log.Fields{"method": optionsMethod, "uri": r.RequestURI}).
 Debug("HTTP request received")
 if enableCors {
 writeCorsHeaders(w, r)
 }
 context.apiVersion = mux.Vars(r)["version"]
 optionsFct(context, w, r)
 }
 r.Path("/v{version:[0-9]+.[0-9]+}" + localRoute).
 Methods(optionsMethod).HandlerFunc(wrap)
 r.Path(localRoute).Methods(optionsMethod).
 HandlerFunc(wrap)
 }
 }
 }
}

var routes = map[string]map[string]handler{
 "HEAD": {
 "/containers/{name:.*}/archive": proxyContainer,
 },
 "GET": {
 "/_ping": ping,
 "/events": getEvents,
 "/info": getInfo,
 ......
 }
 ......
}

"HEAD": {
 "/containers/{name:.*}/archive": proxyContainer,
}

{
 "/containers/{name:.*}/archive": proxyContainer,
}

r.Path("/v{version:[0-9]+.[0-9]+}" + localRoute).Methods(localMethod).HandlerFunc(wrap)
r.Path(localRoute).Methods(localMethod).HandlerFunc(wrap)

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