编写Kubernetes风格的APIServer
前段时间接到一个需求做一个工具,工具将在K8S中运行。需求很适合用控制器模式实现,很自然的就基于kubebuilder进行开发了。但是和K8S环境提供方沟通时发现,他们不允许工作负载调用控制平面的接口,这该怎么办呢。
最快速的解决方案是,自己运行一套kube-apiserver + etcd。但是这对我们来说太重了,kube-apiserver很多我们不需要的特性占用了过多资源,因此这里想寻找一个更轻量的方案。
kubernetes/apiserver同步自kubernertes主代码树的taging/src/k8s.io/apiserver目录,它提供了创建K8S风格的API Server所需要的库。包括kube-apiserver、kube-aggregator、service-catalog在内的很多项目都依赖此库。
apiserver库的目的主要是用来构建API Aggregation中的Extension API Server。它提供的特性包括:
- 将authn/authz委托给主kube-apiserver
- 支持kuebctl兼容的API发现
- 支持admisson control链
- 支持版本化的API类型
K8S提供了一个样例kubernetes/sample-apiserver,但是这个例子依赖于主kube-apiserver。即使不使用authn/authz或API聚合,也是如此。你需要通过--kubeconfig来指向一个主kube-apiserver,样例中的SharedInformer依赖于会连接到主kube-apiserver来访问K8S资源。
显然我们是不能对主kube-apiserver有任何依赖的,这里分析一下sample-apiserver的代码,看看如何进行改动。
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func main() { logs.InitLogs() defer logs.FlushLogs() stopCh := genericapiserver.SetupSignalHandler() // 初始化服务器选项 options := server.NewWardleServerOptions(os.Stdout, os.Stderr) // 启动服务器 cmd := server.NewCommandStartWardleServer(options, stopCh) cmd.Flags().AddGoFlagSet(flag.CommandLine) if err := cmd.Execute(); err != nil { klog.Fatal(err) } } |
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type WardleServerOptions struct { RecommendedOptions *genericoptions.RecommendedOptions SharedInformerFactory informers.SharedInformerFactory StdOut io.Writer StdErr io.Writer } func NewWardleServerOptions(out, errOut io.Writer) *WardleServerOptions { o := &WardleServerOptions{ RecommendedOptions: genericoptions.NewRecommendedOptions( // 数据默认存放在Etcd的/registry/wardle.example.com目录下 defaultEtcdPathPrefix, // 指定wardle.example.com/v1alpha1使用遗留编解码器 apiserver.Codecs.LegacyCodec(v1alpha1.SchemeGroupVersion), // API Server的进程信息 genericoptions.NewProcessInfo("wardle-apiserver", "wardle"), ), StdOut: out, StdErr: errOut, } // wardle.example.com/v1alpha1中的所有对象存储到Etcd o.RecommendedOptions.Etcd.StorageConfig.EncodeVersioner = runtime.NewMultiGroupVersioner(v1alpha1.SchemeGroupVersion, schema.GroupKind{Group: v1alpha1.GroupName}) return o } |
可以看到,选项的核心是genericoptions.RecommendedOptions,顾名思义,它用于提供运行apiserver所需的“推荐”选项:
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type RecommendedOptions struct { // Etcd相关的配置 Etcd *EtcdOptions // HTTPS相关选项,包括监听地址、证书等配置。还负责创建并设置Lookback专用的rest.Config SecureServing *SecureServingOptionsWithLoopback // authn选项 Authentication *DelegatingAuthenticationOptions // authz选项 Authorization *DelegatingAuthorizationOptions // 审计选项 Audit *AuditOptions // 用于启用剖析、竞态条件剖析 Features *FeatureOptions // 核心API选项,指定主kube-apiserver配置文件位置 CoreAPI *CoreAPIOptions // 特性开关 FeatureGate featuregate.FeatureGate // 所有以上选项的ApplyTo被调用后,调用下面的函数。返回的PluginInitializer会传递给Admission.ApplyTo ExtraAdmissionInitializers func(c *server.RecommendedConfig) ([]admission.PluginInitializer, error) Admission *AdmissionOptions // 提供服务器信息 ProcessInfo *ProcessInfo // Webhook选项 Webhook *WebhookOptions // 控制服务器的出站流量 EgressSelector *EgressSelectorOptions } |
推荐的选项取值,可以由函数genericoptions.NewRecommendedOptions()提供。RecommendedOptions支持通过命令行参数获取选项取值:
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func (o *RecommendedOptions) AddFlags(fs *pflag.FlagSet) {} |
服务器实现为cobra.Command命令,首先会将RecommendedOptions绑定到命令行参数。
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func NewCommandStartWardleServer(defaults *WardleServerOptions, stopCh <-chan struct{}) *cobra.Command { o := *defaults cmd := &cobra.Command{ Short: "Launch a wardle API server", Long: "Launch a wardle API server", RunE: func(c *cobra.Command, args []string) error { // ... }, } flags := cmd.Flags() // 将选项添加为命令行标记 o.RecommendedOptions.AddFlags(flags) utilfeature.DefaultMutableFeatureGate.AddFlag(flags) return cmd } |
然后,调用cmd.Execute(),进而调用上面的RunE方法:
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if err := o.Complete(); err != nil { return err } if err := o.Validate(args); err != nil { return err } if err := o.RunWardleServer(stopCh); err != nil { return err } return nil |
Complete方法,就是注册了一个Admission控制器,参考下文。
Validate方法调用RecommendedOptions进行选项(合并了用户提供的命令行标记)合法性校验:
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func (o WardleServerOptions) Validate(args []string) error { errors := []error{} // 校验结果是错误的切片 errors = append(errors, o.RecommendedOptions.Validate()...) // 合并为单个错误 return utilerrors.NewAggregate(errors) } |
RunWardleServer方法启动API Server。它包含了将服务器选项(Option)转换为服务器配置(Config),从服务器配置实例化APIServer,并运行APIServer的整个流程:
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func (o WardleServerOptions) RunWardleServer(stopCh <-chan struct{}) error { // 选项转换为配置 config, err := o.Config() if err != nil { return err } // 配置转换为CompletedConfig,实例化APIServer server, err := config.Complete().New() if err != nil { return err } // 注册一个在API Server启动之后运行的钩子 server.GenericAPIServer.AddPostStartHookOrDie("start-sample-server-informers", func(context genericapiserver.PostStartHookContext) error { config.GenericConfig.SharedInformerFactory.Start(context.StopCh) o.SharedInformerFactory.Start(context.StopCh) return nil }) // 准备运行、 运行 APIServer return server.GenericAPIServer.PrepareRun().Run(stopCh) } |
API Server不能直接使用选项,必须将选项转换为apiserver.Config:
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func (o *WardleServerOptions) Config() (*apiserver.Config, error) { // 这里又对选项进行了若干修改 // 检查证书是否可以读取,如果不可以则尝试生成自签名证书 if err := o.RecommendedOptions.SecureServing.MaybeDefaultWithSelfSignedCerts("localhost", nil, []net.IP{net.ParseIP("127.0.0.1")}); err != nil { return nil, fmt.Errorf("error creating self-signed certificates: %v", err) } // 根据特性开关,决定是否支持分页 o.RecommendedOptions.Etcd.StorageConfig.Paging = utilfeature.DefaultFeatureGate.Enabled(features.APIListChunking) // o.RecommendedOptions.ExtraAdmissionInitializers = func(c *genericapiserver.RecommendedConfig) ([]admission.PluginInitializer, error) { // ... } // 创建推荐配置 serverConfig := genericapiserver.NewRecommendedConfig(apiserver.Codecs) // 暴露OpenAPI端点 serverConfig.OpenAPIConfig = genericapiserver.DefaultOpenAPIConfig( // 自动生成的 sampleopenapi.GetOpenAPIDefinitions, openapi.NewDefinitionNamer(apiserver.Scheme)) serverConfig.OpenAPIConfig.Info.Title = "Wardle" serverConfig.OpenAPIConfig.Info.Version = "0.1" // 将RecommendedOptions应用到RecommendedConfig if err := o.RecommendedOptions.ApplyTo(serverConfig); err != nil { return nil, err } // 选项包含GenericConfig和你自定义的选项两部分 config := &apiserver.Config{ GenericConfig: serverConfig, ExtraConfig: apiserver.ExtraConfig{}, } return config, nil } |
从上面的代码可以看到RecommendedConfig是配置的核心:
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type RecommendedConfig struct { // 用于配置GenericAPIServer的结构 Config // SharedInformerFactory用于提供K8S资源的shared informers // 该字段由RecommendedOptions.CoreAPI.ApplyTo调用设置,informer默认使用in-cluster的ClientConfig SharedInformerFactory informers.SharedInformerFactory // 由RecommendedOptions.CoreAPI.ApplyTo设置,informer使用 ClientConfig *restclient.Config } type Config struct { SecureServing *SecureServingInfo Authentication AuthenticationInfo Authorization AuthorizationInfo // 特权的本机使用的ClientConfig,PostStartHooks用到它 LoopbackClientConfig *restclient.Config // ... } |
通过调用ApplyTo方法,将RecommendedOptions中的选项传递给了RecommendedConfig:
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func (o *RecommendedOptions) ApplyTo(config *server.RecommendedConfig) error { // 调用config.AddHealthChecks添加Etcd的健康检查 // 设置config.RESTOptionsGetter if err := o.Etcd.ApplyTo(&config.Config); err != nil { return err } // 创建config.Listener // 初始化config.Cert、config.CipherSuites、config.SNICerts等 if err := o.SecureServing.ApplyTo(&config.Config.SecureServing, &config.Config.LoopbackClientConfig); err != nil { return err } // 初始化身份验证配置,获取相应的K8S客户端接口 if err := o.Authentication.ApplyTo(&config.Config.Authentication, config.SecureServing, config.OpenAPIConfig); err != nil { return err } // 初始化访问控制配置,获取相应的K8S客户端接口 if err := o.Authorization.ApplyTo(&config.Config.Authorization); err != nil { return err } if err := o.Audit.ApplyTo(&config.Config, config.ClientConfig, config.SharedInformerFactory, o.ProcessInfo, o.Webhook); err != nil { return err } if err := o.Features.ApplyTo(&config.Config); err != nil { return err } // 从配置文件加载kubeconfig或者使用incluster配置,提供config.ClientConfig和config.SharedInformerFactory if err := o.CoreAPI.ApplyTo(config); err != nil { return err } // 调用Admission初始化器 if initializers, err := o.ExtraAdmissionInitializers(config); err != nil { return err // 逐个初始化Admission控制器 } else if err := o.Admission.ApplyTo(&config.Config, config.SharedInformerFactory, config.ClientConfig, o.FeatureGate, initializers...); err != nil { return err } if err := o.EgressSelector.ApplyTo(&config.Config); err != nil { return err } if feature.DefaultFeatureGate.Enabled(features.APIPriorityAndFairness) { config.FlowControl = utilflowcontrol.New( config.SharedInformerFactory, kubernetes.NewForConfigOrDie(config.ClientConfig).FlowcontrolV1alpha1(), config.MaxRequestsInFlight+config.MaxMutatingRequestsInFlight, config.RequestTimeout/4, ) } return nil } |
可以看到,在生成服务器配置的阶段,对主kube-apiserver有强依赖,这些依赖导致了sample-apiserver无法脱离K8S独立运行。
RecommendedConfig还需要通过Conplete方法,变成CompletedConfig:
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// server, err := config.Complete().New() func (cfg *Config) Complete() CompletedConfig { c := completedConfig{ cfg.GenericConfig.Complete(), &cfg.ExtraConfig, } c.GenericConfig.Version = &version.Info{ Major: "1", Minor: "0", } return CompletedConfig{&c} } // Complete补全缺失的、必须的配置信息,这些信息能够从已有配置导出 func (c *RecommendedConfig) Complete() CompletedConfig { return c.Config.Complete(c.SharedInformerFactory) } |
WardleServer,是从CompletedConfig实例化的:
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func (c completedConfig) New() (*WardleServer, error) { // 创建GenericAPIServer // 名字用于在记录日志时进行区分 // DelegationTarget用于进行APIServer的组合(composition) genericServer, err := c.GenericConfig.New("sample-apiserver", genericapiserver.NewEmptyDelegate()) if err != nil { return nil, err } s := &WardleServer{ GenericAPIServer: genericServer, } |
上面的 New()创建了核心的GenericAPIServer:
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func (c completedConfig) New(name string, delegationTarget DelegationTarget) (*GenericAPIServer, error) { // 断言 if c.Serializer == nil { return nil, fmt.Errorf("Genericapiserver.New() called with config.Serializer == nil") } if c.LoopbackClientConfig == nil { return nil, fmt.Errorf("Genericapiserver.New() called with config.LoopbackClientConfig == nil") } if c.EquivalentResourceRegistry == nil { return nil, fmt.Errorf("Genericapiserver.New() called with config.EquivalentResourceRegistry == nil") } handlerChainBuilder := func(handler http.Handler) http.Handler { return c.BuildHandlerChainFunc(handler, c.Config) } // 构建请求处理器 apiServerHandler := NewAPIServerHandler(name, c.Serializer, handlerChainBuilder, delegationTarget.UnprotectedHandler()) // 创建GenericAPIServer,很多字段直接来自completedConfig s := &GenericAPIServer{ discoveryAddresses: c.DiscoveryAddresses, LoopbackClientConfig: c.LoopbackClientConfig, legacyAPIGroupPrefixes: c.LegacyAPIGroupPrefixes, admissionControl: c.AdmissionControl, Serializer: c.Serializer, AuditBackend: c.AuditBackend, Authorizer: c.Authorization.Authorizer, delegationTarget: delegationTarget, EquivalentResourceRegistry: c.EquivalentResourceRegistry, HandlerChainWaitGroup: c.HandlerChainWaitGroup, minRequestTimeout: time.Duration(c.MinRequestTimeout) * time.Second, ShutdownTimeout: c.RequestTimeout, ShutdownDelayDuration: c.ShutdownDelayDuration, SecureServingInfo: c.SecureServing, ExternalAddress: c.ExternalAddress, Handler: apiServerHandler, listedPathProvider: apiServerHandler, openAPIConfig: c.OpenAPIConfig, skipOpenAPIInstallation: c.SkipOpenAPIInstallation, postStartHooks: map[string]postStartHookEntry{}, preShutdownHooks: map[string]preShutdownHookEntry{}, disabledPostStartHooks: c.DisabledPostStartHooks, healthzChecks: c.HealthzChecks, livezChecks: c.LivezChecks, readyzChecks: c.ReadyzChecks, readinessStopCh: make(chan struct{}), livezGracePeriod: c.LivezGracePeriod, DiscoveryGroupManager: discovery.NewRootAPIsHandler(c.DiscoveryAddresses, c.Serializer), maxRequestBodyBytes: c.MaxRequestBodyBytes, livezClock: clock.RealClock{}, } // ... // 添加delegationTarget的生命周期钩子 for k, v := range delegationTarget.PostStartHooks() { s.postStartHooks[k] = v } for k, v := range delegationTarget.PreShutdownHooks() { s.preShutdownHooks[k] = v } // 添加预配置的钩子 for name, preconfiguredPostStartHook := range c.PostStartHooks { if err := s.AddPostStartHook(name, preconfiguredPostStartHook.hook); err != nil { return nil, err } } // 如果配置包含了SharedInformerFactory,而启动该SharedInformerFactory的钩子没有注册 // 则注册一个PostStart钩子来启动它 genericApiServerHookName := "generic-apiserver-start-informers" if c.SharedInformerFactory != nil { if !s.isPostStartHookRegistered(genericApiServerHookName) { err := s.AddPostStartHook(genericApiServerHookName, func(context PostStartHookContext) error { c.SharedInformerFactory.Start(context.StopCh) return nil }) if err != nil { return nil, err } // TODO: Once we get rid of /healthz consider changing this to post-start-hook. err = s.addReadyzChecks(healthz.NewInformerSyncHealthz(c.SharedInformerFactory)) if err != nil { return nil, err } } } const priorityAndFairnessConfigConsumerHookName = "priority-and-fairness-config-consumer" if s.isPostStartHookRegistered(priorityAndFairnessConfigConsumerHookName) { } else if c.FlowControl != nil { err := s.AddPostStartHook(priorityAndFairnessConfigConsumerHookName, func(context PostStartHookContext) error { go c.FlowControl.Run(context.StopCh) return nil }) if err != nil { return nil, err } // TODO(yue9944882): plumb pre-shutdown-hook for request-management system? } else { klog.V(3).Infof("Not requested to run hook %s", priorityAndFairnessConfigConsumerHookName) } // 添加delegationTarget的健康检查 for _, delegateCheck := range delegationTarget.HealthzChecks() { skip := false for _, existingCheck := range c.HealthzChecks { if existingCheck.Name() == delegateCheck.Name() { skip = true break } } if skip { continue } s.AddHealthChecks(delegateCheck) } s.listedPathProvider = routes.ListedPathProviders{s.listedPathProvider, delegationTarget} // 安装Profiling、Metrics、URL / 下显示的路径列表(listedPathProvider) installAPI(s, c.Config) // use the UnprotectedHandler from the delegation target to ensure that we don't attempt to double authenticator, authorize, // or some other part of the filter chain in delegation cases. if delegationTarget.UnprotectedHandler() == nil && c.EnableIndex { s.Handler.NonGoRestfulMux.NotFoundHandler(routes.IndexLister{ StatusCode: http.StatusNotFound, PathProvider: s.listedPathProvider, }) } return s, nil } |
GenericAPIServer.Handler就是HTTP请求的处理器,我们在下文的请求处理过程一节分析。
实例化GenericAPIServer之后,是安装APIGroup:
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// 创建APIGroupInfo,关于一组API的各种信息,包括已经注册的API(Scheme),如何进行编解码(Codec) // 如何解析查询参数(ParameterCodec) apiGroupInfo := genericapiserver.NewDefaultAPIGroupInfo(wardle.GroupName, Scheme, metav1.ParameterCodec, Codecs) // 从资源到rest.Storage的映射 v1alpha1storage := map[stcongring]rest.Storage{} v1alpha1storage["flunders"] = wardleregistry.RESTInPeace(flunderstorage.NewREST(Scheme, c.GenericConfig.RESTOptionsGetter)) v1alpha1storage["fischers"] = wardleregistry.RESTInPeace(fischerstorage.NewREST(Scheme, c.GenericConfig.RESTOptionsGetter)) // 两个版本分别对应一个映射 apiGroupInfo.VersionedResourcesStorageMap["v1alpha1"] = v1alpha1storage v1beta1storage := map[string]rest.Storage{} v1beta1storage["flunders"] = wardleregistry.RESTInPeace(flunderstorage.NewREST(Scheme, c.GenericConfig.RESTOptionsGetter)) apiGroupInfo.VersionedResourcesStorageMap["v1beta1"] = v1beta1storage if err := s.GenericAPIServer.InstallAPIGroup(&apiGroupInfo); err != nil { return nil, err } return s, nil } |
上面的flunderstorage.NewREST等方法返回的registry.REST,内嵌的genericregistry.Store不仅仅实现了rest.Storage:
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type Storage interface { // 当请求的数据存放到该方法创建的对象之后,可以调用Create/Update进行持久化 // 必须返回一个适用于 Codec.DecodeInto([]byte, runtime.Object) 的指针类型 New() runtime.Object } |
还实现了rest.StandardStorage:
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type StandardStorage interface { Getter Lister CreaterUpdater GracefulDeleter CollectionDeleter Watcher } |
实现了这些接口,意味着registry.REST能够支持API对象的增删改查和Watch。更多细节我们在下面的请求处理过程一节中探讨。
如启动服务器一节中的代码所示, 在将选项转换为配置、完成配置,并从配置实例化APIServer之后,会执行由两个步骤组成的启动逻辑。
首先是PrepareRun,这里执行一些需要在API安装(在实例化时)之后进行的操作:
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func (s *GenericAPIServer) PrepareRun() preparedGenericAPIServer { s.delegationTarget.PrepareRun() // 安装OpenAPI的Handler if s.openAPIConfig != nil && !s.skipOpenAPIInstallation { s.OpenAPIVersionedService, s.StaticOpenAPISpec = routes.OpenAPI{ Config: s.openAPIConfig, }.Install(s.Handler.GoRestfulContainer, s.Handler.NonGoRestfulMux) } // 安装健康检查的Handler s.installHealthz() s.installLivez() err := s.addReadyzShutdownCheck(s.readinessStopCh) if err != nil { klog.Errorf("Failed to install readyz shutdown check %s", err) } s.installReadyz() // 为审计后端注册关闭前钩子 if s.AuditBackend != nil { err := s.AddPreShutdownHook("audit-backend", func() error { s.AuditBackend.Shutdown() return nil }) if err != nil { klog.Errorf("Failed to add pre-shutdown hook for audit-backend %s", err) } } return preparedGenericAPIServer{s} } |
然后是Run,启动APIServer:
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func (s preparedGenericAPIServer) Run(stopCh <-chan struct{}) error { delayedStopCh := make(chan struct{}) go func() { defer close(delayedStopCh) // 收到关闭信号 <-stopCh // 一旦关闭流程被触发,/readyz就需要立刻返回错误 close(s.readinessStopCh) // 关闭服务器前休眠ShutdownDelayDuration,这让LB有个时间窗口来检测/readyz状态,不再发送请求给此服务器 time.Sleep(s.ShutdownDelayDuration) }() // 运行服务器 err := s.NonBlockingRun(delayedStopCh) if err != nil { return err } // 收到关闭信号 <-stopCh // 运行关闭前钩子 err = s.RunPreShutdownHooks() if err != nil { return err } // 等待延迟关闭信号 <-delayedStopCh // 等待现有请求完毕,然后关闭 s.HandlerChainWaitGroup.Wait() return nil } |
NonBlockingRun是启动APIServer的核心代码。它会启动一个HTTPS服务器:
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func (s preparedGenericAPIServer) NonBlockingRun(stopCh <-chan struct{}) error { // 这个通道用于保证HTTP Server优雅关闭,不会导致丢失审计事件 auditStopCh := make(chan struct{}) // 首先启动审计后端,这时任何请求都进不来 if s.AuditBackend != nil { if err := s.AuditBackend.Run(auditStopCh); err != nil { return fmt.Errorf("failed to run the audit backend: %v", err) } } // 下面的通道用于出错时清理listener internalStopCh := make(chan struct{}) var stoppedCh <-chan struct{} if s.SecureServingInfo != nil && s.Handler != nil { var err error // 启动HTTPS服务器,仅当证书错误或内部listen调用出错时会失败 // server loop在一个Goroutine中运行 // 可以看到,这里的s.Handler是可以被我们访问到的,因此建立HTTP(非HTTPS)服务器应该很方便 stoppedCh, err = s.SecureServingInfo.Serve(s.Handler, s.ShutdownTimeout, internalStopCh) if err != nil { close(internalStopCh) close(auditStopCh) return err } } // 清理 go func() { <-stopCh close(internalStopCh) if stoppedCh != nil { <-stoppedCh } s.HandlerChainWaitGroup.Wait() close(auditStopCh) }() // 启动后钩子 s.RunPostStartHooks(stopCh) if _, err := systemd.SdNotify(true, "READY=1\n"); err != nil { klog.Errorf("Unable to send systemd daemon successful start message: %v\n", err) } return nil } |
apis/wardle包,以及它的子包,定义了wardle.example.com组的API。
wardle包的register.go中定义了组,以及从GV获得GVK、GVR的函数:
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const GroupName = "wardle.example.com" // 没有正式(formal)类型则使用此常量 var SchemeGroupVersion = schema.GroupVersion{Group: GroupName, Version: runtime.APIVersionInternal} func Kind(kind string) schema.GroupKind { return SchemeGroupVersion.WithKind(kind).GroupKind() } func Resource(resource string) schema.GroupResource { return SchemeGroupVersion.WithResource(resource).GroupResource() } |
API包通常都要提供AddToScheme变量,用于将API注册到指定的scheme:
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var ( SchemeBuilder = runtime.NewSchemeBuilder(addKnownTypes) AddToScheme = SchemeBuilder.AddToScheme ) func addKnownTypes(scheme *runtime.Scheme) error { // 注册API的核心,添加GV中的若干API类型 scheme.AddKnownTypes(SchemeGroupVersion, &Flunder{}, // 必须提供指针类型,Go反射得到类型在编码时作为Kind &FlunderList{}, &Fischer{}, &FischerList{}, ) return nil } // 所谓SchemeBuilder其实就是切片 type SchemeBuilder []func(*Scheme) error // NewSchemeBuilder方法支持多个回调函数,对这些函数调用SchemeBuilder.Register func NewSchemeBuilder(funcs ...func(*Scheme) error) SchemeBuilder { var sb SchemeBuilder sb.Register(funcs...) return sb } // 所谓Register就是添加到切片中 func (sb *SchemeBuilder) Register(funcs ...func(*Scheme) error) { for _, f := range funcs { *sb = append(*sb, f) } } // 所谓AddToScheme就是遍历回调,Go方法可以作为变量传递 func (sb *SchemeBuilder) AddToScheme(s *Scheme) error { for _, f := range *sb { if err := f(s); err != nil { return err } } return nil } |
wardle包的types.go则定义了API类型对应的Go结构体。
子包v1alpha1、v1beta1定义了API的两个版本。它们包含和wardle包类似的GroupName、SchemeGroupVersion、SchemeBuilder、AddToScheme…等变量/函数,以及对应的API类型结构体。还包括自动生成的、与APIVersionInternal版本API进行转换的函数。
回到wardle包,Install方法支持将APIVersionInternal、v1alpha1、v1beta1这些版本都注册到scheme:
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func Install(scheme *runtime.Scheme) { utilruntime.Must(wardle.AddToScheme(scheme)) utilruntime.Must(v1beta1.AddToScheme(scheme)) utilruntime.Must(v1alpha1.AddToScheme(scheme)) utilruntime.Must(scheme.SetVersionPriority(v1beta1.SchemeGroupVersion, v1alpha1.SchemeGroupVersion)) } |
而在apiserver包中,在init时会调用上面的Install函数:
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var ( // API注册表 Scheme = runtime.NewScheme() // 编解码器工厂 Codecs = serializer.NewCodecFactory(Scheme) ) func init() { // 安装sample-apiserver提供的API install.Install(Scheme) // 将k8s.io/apimachinery/pkg/apis/meta/v1"注册到v1组,为什么? // we need to add the options to empty v1 // TODO fix the server code to avoid this metav1.AddToGroupVersion(Scheme, schema.GroupVersion{Version: "v1"}) // TODO: keep the generic API server from wanting this unversioned := schema.GroupVersion{Group: "", Version: "v1"} Scheme.AddUnversionedTypes(unversioned, &metav1.Status{}, &metav1.APIVersions{}, &metav1.APIGroupList{}, &metav1.APIGroup{}, &metav1.APIResourceList{}, ) } |
Codecs是API资源编解码器的工厂,RecommendedOptions需要此工厂:
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// ... RecommendedOptions: genericoptions.NewRecommendedOptions( defaultEtcdPathPrefix, // 得到v1alpha1版本的LegacyCodec,遗留编解码器(runtime.Codec) // LegacyCodec编码到指定的API版本,解码(从任何支持的源)到内部形式 // 此编码器总是编码为JSON // // LegacyCodec方法已经废弃,客户端/服务器应该根据MIME类型协商serializer // 并调用CodecForVersions apiserver.Codecs.LegacyCodec(v1alpha1.SchemeGroupVersion), genericoptions.NewProcessInfo("wardle-apiserver", "wardle"), ), func NewRecommendedOptions(prefix string, codec runtime.Codec, processInfo *ProcessInfo) *RecommendedOptions { return &RecommendedOptions{ // 不过这里的runtime.Codec用于将AP对象转换为JSON并存放到Etcd,而不是发给客户端 Etcd: NewEtcdOptions(storagebackend.NewDefaultConfig(prefix, codec)), // ... |
APIGroupInfo也需要此工厂:
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apiGroupInfo := genericapiserver.NewDefaultAPIGroupInfo(wardle.GroupName, Scheme, metav1.ParameterCodec, Codecs) func NewDefaultAPIGroupInfo(group string, scheme *runtime.Scheme, parameterCodec runtime.ParameterCodec, codecs serializer.CodecFactory) APIGroupInfo { return APIGroupInfo{ // ... Scheme: scheme, ParameterCodec: parameterCodec, NegotiatedSerializer: codecs, } } |
在APIServer实例化期间,Scheme会传递给APIGroupInfo,从而实现资源 - Go类型之间的映射。
sample-server也示例了如何集成自己的Admission控制器到API Server中。
在选项中,需要注册一个Admission初始化器
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o.RecommendedOptions.ExtraAdmissionInitializers = func(c *genericapiserver.RecommendedConfig) ([]admission.PluginInitializer, error) { client, err := clientset.NewForConfig(c.LoopbackClientConfig) if err != nil { return nil, err } informerFactory := informers.NewSharedInformerFactory(client, c.LoopbackClientConfig.Timeout) o.SharedInformerFactory = informerFactory // 初始化函数 return []admission.PluginInitializer{wardleinitializer.New(informerFactory)}, nil } |
初始化器是一个函数,会在选项转为配置的时候执行:
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// 调用上面的函数 if initializers, err := o.ExtraAdmissionInitializers(config); err != nil { return err // 初始化Admission控制器 } else if err := o.Admission.ApplyTo(&config.Config, config.SharedInformerFactory, config.ClientConfig, o.FeatureGate, initializers...); err != nil { return err } |
上面的ApplyTo方法,会组建一个Admission控制器的初始化函数链,并逐个调用,以初始化所有Admission控制器。
此外,在PostStart钩子中,会启动Admission控制器所依赖的SharedInformerFactory:
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server.GenericAPIServer.AddPostStartHookOrDie("start-sample-server-informers", func(context genericapiserver.PostStartHookContext) error { // 主kube-apiserver的InformerFactory,貌似没什么用 config.GenericConfig.SharedInformerFactory.Start(context.StopCh) // 次级kube-apiserver的InformerFactory,Admission控制器需要使用 o.SharedInformerFactory.Start(context.StopCh) return nil }) |
我们看一下sample-apiserver的Admission相关代码。
位于pkg/admission/wardleinitializer包中的是Admission初始化器,它能够为任何WantsInternalWardleInformerFactory类型的Admission控制器注入InformerFactory:
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type pluginInitializer struct { informers informers.SharedInformerFactory } var _ admission.PluginInitializer = pluginInitializer{} // 该函数在ExtraAdmissionInitializers函数中调用 func New(informers informers.SharedInformerFactory) pluginInitializer { return pluginInitializer{ informers: informers, } } // 该函数在o.Admission.ApplyTo中调用 func (i pluginInitializer) Initialize(plugin admission.Interface) { if wants, ok := plugin.(WantsInternalWardleInformerFactory); ok { wants.SetInternalWardleInformerFactory(i.informers) } } |
位于pkg/admission/plugin/banflunder包中的是为了的Admission控制器BanFlunder。函数:
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func Register(plugins *admission.Plugins) { plugins.Register("BanFlunder", func(config io.Reader) (admission.Interface, error) { return New() }) } |
会在程序运行的很早期调用,以注册Admission控制器到API Server:
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func (o *WardleServerOptions) Complete() error { // 注册插件 banflunder.Register(o.RecommendedOptions.Admission.Plugins) // 配置顺序 o.RecommendedOptions.Admission.RecommendedPluginOrder = append(o.RecommendedOptions.Admission.RecommendedPluginOrder, "BanFlunder") return nil } |
Admission控制器的核心是Admit函数,它可以修改或否决一个API Server请求:
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func (d *DisallowFlunder) Admit(ctx context.Context, a admission.Attributes, o admission.ObjectInterfaces) error { // 仅仅对特定类型的API感兴趣 if a.GetKind().GroupKind() != wardle.Kind("Flunder") { return nil } if !d.WaitForReady() { return admission.NewForbidden(a, fmt.Errorf("not yet ready to handle request")) } // 用于获取元数据 metaAccessor, err := meta.Accessor(a.GetObject()) if err != nil { return err } flunderName := metaAccessor.GetName() fischers, err := d.lister.List(labels.Everything()) if err != nil { return err } for _, fischer := range fischers { for _, disallowedFlunder := range fischer.DisallowedFlunders { if flunderName == disallowedFlunder { return errors.NewForbidden( a.GetResource().GroupResource(), a.GetName(), // 拒绝请求 fmt.Errorf("this name may not be used, please change the resource name"), ) } } } return nil } |
通过上文的分析,我们知道资源的增删改查是由registry.REST(空壳,实际是genericregistry.Store)负责的,那么HTTP请求是如何传递给它的呢?
回顾一下向APIGroupInfo中添加资源的代码:
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// 资源类型 v1alpha1storage["flunders"] = wardleregistry.RESTInPeace( // 创建registry.REST flunderstorage.NewREST(Scheme, c.GenericConfig.RESTOptionsGetter) ) func NewREST(scheme *runtime.Scheme, optsGetter generic.RESTOptionsGetter) (*registry.REST, error) { // 策略,参考下文 strategy := NewStrategy(scheme) store := &genericregistry.Store{ // 实例化资源的函数 NewFunc: func() runtime.Object { // 每次增删改查,都牵涉到结构的创建,因此在此打断点可以拦截所有请求 return &wardle.Flunder{} }, // 实例化资源列表的函数 NewListFunc: func() runtime.Object { return &wardle.FlunderList{} }, // 判断对象是否可以被该存储处理 PredicateFunc: func(label labels.Selector, field fields.Selector) storage.SelectionPredicate { return storage.SelectionPredicate{ Label: label, Field: field, GetAttrs: func(obj runtime.Object) (labels.Set, fields.Set, error) { apiserver, ok := obj.(*wardle.Flunder) if !ok { return nil, nil, fmt.Errorf("given object is not a Flunder") } return apiserver.ObjectMeta.Labels, SelectableFields(apiserver), nil }, } }, // 资源的复数名称,当上下文中缺少必要的请求信息时使用 DefaultQualifiedResource: wardle.Resource("flunders"), // 增删改的策略 CreateStrategy: strategy, UpdateStrategy: strategy, DeleteStrategy: strategy, } options := &generic.StoreOptions{RESTOptions: optsGetter, AttrFunc: GetAttrs} // 填充默认字段 if err := store.CompleteWithOptions(options); err != nil { return nil, err } return ®istry.REST{store}, nil } |
为了创建genericregistry.Store,需要两个信息:
- Scheme,它提供的信息是Go类型和GVK之间的映射关系。其中Kind是根据Go结构的类型名反射得到的
- generic.RESTOptionsGetter
RESTOptionsGetter用于获得RESTOptions:
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type RESTOptionsGetter interface { GetRESTOptions(resource schema.GroupResource) (RESTOptions, error) } |
RESTOptions包含了关于存储的信息,尽管这个职责和名字好像没什么关系:
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type RESTOptions struct { // 创建一个存储后端所需的配置信息 StorageConfig *storagebackend.Config // 这是一个函数,能够提供storage.Interface和factory.DestroyFunc Decorator StorageDecorator EnableGarbageCollection bool DeleteCollectionWorkers int ResourcePrefix string CountMetricPollPeriod time.Duration } // type Config struct { // 存储后端的类型,默认etcd3 Type string // 传递给storage.Interface的所有方法的前缀,对应etcd存储前缀 Prefix string // 连接到Etcd服务器的相关信息 Transport TransportConfig // 提示APIServer是否应该支持分页 Paging bool // 负责(反)串行化 Codec runtime.Codec // 在持久化到Etcd之前,该对象输出目标将被转换为的GVK Transformer value.Transformer CompactionInterval time.Duration CountMetricPollPeriod time.Duration LeaseManagerConfig etcd3.LeaseManagerConfig } // 利用入参函数,构造storage.Interface type StorageDecorator func( config *storagebackend.Config, resourcePrefix string, keyFunc func(obj runtime.Object) (string, error), newFunc func() runtime.Object, newListFunc func() runtime.Object, getAttrsFunc storage.AttrFunc, trigger storage.IndexerFuncs, indexers *cache.Indexers) (storage.Interface, factory.DestroyFunc, error) // CRUD type Interface interface { Versioner() Versioner Create(ctx context.Context, key string, obj, out runtime.Object, ttl uint64) error Delete(ctx context.Context, key string, out runtime.Object, preconditions *Preconditions, validateDeletion ValidateObjectFunc) error Watch(ctx context.Context, key string, resourceVersion string, p SelectionPredicate) (watch.Interface, error) WatchList(ctx context.Context, key string, resourceVersion string, p SelectionPredicate) (watch.Interface, error) Get(ctx context.Context, key string, resourceVersion string, objPtr runtime.Object, ignoreNotFound bool) error GetToList(ctx context.Context, key string, resourceVersion string, p SelectionPredicate, listObj runtime.Object) error List(ctx context.Context, key string, resourceVersion string, p SelectionPredicate, listObj runtime.Object) error GuaranteedUpdate( ctx context.Context, key string, ptrToType runtime.Object, ignoreNotFound bool, precondtions *Preconditions, tryUpdate UpdateFunc, suggestion ...runtime.Object) error Count(key string) (int64, error) } // 这个函数用于一次性销毁任何Create()创建的、当前Storage使用的对象 type DestroyFunc func() |
在这里我们可以注意到storagebackend.Config和Etcd是有耦合的,因此想支持其它存储后端,需要在更早的节点介入。
genericregistry.Store还包含了三个Strategy字段:
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type Store struct { // ... CreateStrategy rest.RESTCreateStrategy UpdateStrategy rest.RESTUpdateStrategy DeleteStrategy rest.RESTDeleteStrategy // ... } type RESTCreateStrategy interface { runtime.ObjectTyper // 用于生成名称 names.NameGenerator // 对象是否必须在命名空间中 NamespaceScoped() bool // 在Validate、Canonicalize之前调用,进行对象的normalize // 例如删除不需要持久化的字段、对顺序不敏感的列表字段进行重新排序 // 不得移除这样的字段:它不能通过校验 PrepareForCreate(ctx context.Context, obj runtime.Object) // 校验,在对象的默认字段被填充后调用 Validate(ctx context.Context, obj runtime.Object) field.ErrorList // 在校验之后,持久化之前调用。正规化对象,通常实现为类型检查,或空函数 Canonicalize(obj runtime.Object) } type RESTUpdateStrategy interface { runtime.ObjectTyper NamespaceScoped() bool // 对象是否可以被PUT请求创建 AllowCreateOnUpdate() bool // 准备更新 PrepareForUpdate(ctx context.Context, obj, old runtime.Object) // 校验 ValidateUpdate(ctx context.Context, obj, old runtime.Object) field.ErrorList // 正规化 Canonicalize(obj runtime.Object) // 当对象上没有指定版本时,是否允许无条件的更新,也就是不管最新的资源版本(禁用乐观并发控制) AllowUnconditionalUpdate() bool } type RESTDeleteStrategy interface { runtime.ObjectTyper } type ObjectTyper interface { // 得到对象可能的GVK信息 ObjectKinds(Object) ([]schema.GroupVersionKind, bool, error) // Scheme是否支持指定的GVK Recognizes(gvk schema.GroupVersionKind) bool } |
可以看到,策略能够影响增删改的行为,它能够生成对象名称,校验对象合法性,甚至修改对象。 我们看一下sample-apiserver提供的策略实现:
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func NewStrategy(typer runtime.ObjectTyper) flunderStrategy { // 简单命名策略:返回请求的basename外加5位字母数字的随即后缀 return flunderStrategy{typer, names.SimpleNameGenerator} } type flunderStrategy struct { runtime.ObjectTyper names.NameGenerator } func (flunderStrategy) NamespaceScoped() bool { return true } func (flunderStrategy) PrepareForCreate(ctx context.Context, obj runtime.Object) { } func (flunderStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object) { } func (flunderStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList { flunder := obj.(*wardle.Flunder) return validation.ValidateFlunder(flunder) } func (flunderStrategy) AllowCreateOnUpdate() bool { return false } func (flunderStrategy) AllowUnconditionalUpdate() bool { return false } func (flunderStrategy) Canonicalize(obj runtime.Object) { } func (flunderStrategy) ValidateUpdate(ctx context.Context, obj, old runtime.Object) field.ErrorList { return field.ErrorList{} } package validation // ValidateFlunder validates a Flunder. func ValidateFlunder(f *wardle.Flunder) field.ErrorList { allErrs := field.ErrorList{} allErrs = append(allErrs, ValidateFlunderSpec(&f.Spec, field.NewPath("spec"))...) return allErrs } // ValidateFlunderSpec validates a FlunderSpec. func ValidateFlunderSpec(s *wardle.FlunderSpec, fldPath *field.Path) field.ErrorList { allErrs := field.ErrorList{} if len(s.FlunderReference) != 0 && len(s.FischerReference) != 0 { allErrs = append(allErrs, field.Invalid(fldPath.Child("fischerReference"), s.FischerReference, "cannot be set with flunderReference at the same time")) } else if len(s.FlunderReference) != 0 && s.ReferenceType != wardle.FlunderReferenceType { allErrs = append(allErrs, field.Invalid(fldPath.Child("flunderReference"), s.FlunderReference, "cannot be set if referenceType is not Flunder")) } else if len(s.FischerReference) != 0 && s.ReferenceType != wardle.FischerReferenceType { allErrs = append(allErrs, field.Invalid(fldPath.Child("fischerReference"), s.FischerReference, "cannot be set if referenceType is not Fischer")) } else if len(s.FischerReference) == 0 && s.ReferenceType == wardle.FischerReferenceType { allErrs = append(allErrs, field.Invalid(fldPath.Child("fischerReference"), s.FischerReference, "cannot be empty if referenceType is Fischer")) } else if len(s.FlunderReference) == 0 && s.ReferenceType == wardle.FlunderReferenceType { allErrs = append(allErrs, field.Invalid(fldPath.Child("flunderReference"), s.FlunderReference, "cannot be empty if referenceType is Flunder")) } if len(s.ReferenceType) != 0 && s.ReferenceType != wardle.FischerReferenceType && s.ReferenceType != wardle.FlunderReferenceType { allErrs = append(allErrs, field.Invalid(fldPath.Child("referenceType"), s.ReferenceType, "must be Flunder or Fischer")) } return allErrs } |
分析到这里,我们可以猜测到Create请求被genericregistry.Store处理的过程:
- 读取请求体,调用NewFunc反串行化为runtime.Obejct
- 调用PredicateFunc判断是否能够处理该对象
- 调用CreateStrategy,校验、正规化对象
- 调用RESTOptions,存储到Etcd
那么,请求是如何传递过来的,上述处理的细节又是怎样的?上文中我们已经定位到关键代码路径,通过断点很容易跟踪到完整处理流程。
在上文分析的GenericAPIServer实例过程中,它的Handler字段是这样创建的:
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apiServerHandler := NewAPIServerHandler(name, c.Serializer, handlerChainBuilder, delegationTarget.UnprotectedHandler()) // 处理器链的构建器,注意出入参类型一样。这是因为处理器链是一层层包裹的,而不是链表那样的结构 type HandlerChainBuilderFn func(apiHandler http.Handler) http.Handler func NewAPIServerHandler(name string, s runtime.NegotiatedSerializer, handlerChainBuilder HandlerChainBuilderFn, notFoundHandler http.Handler) *APIServerHandler { // 配置go-restful,go-restful是一个构建REST风格WebService的框架 nonGoRestfulMux := mux.NewPathRecorderMux(name) if notFoundHandler != nil { nonGoRestfulMux.NotFoundHandler(notFoundHandler) } // 容器,是一组WebService的集合 gorestfulContainer := restful.NewContainer() // 容器包含一个用户HTTP请求多路复用的ServeMux gorestfulContainer.ServeMux = http.NewServeMux() // 路由器 gorestfulContainer.Router(restful.CurlyRouter{}) // e.g. for proxy/{kind}/{name}/{*} // panic处理器 gorestfulContainer.RecoverHandler(func(panicReason interface{}, httpWriter http.ResponseWriter) { logStackOnRecover(s, panicReason, httpWriter) }) // 错误处理器 gorestfulContainer.ServiceErrorHandler(func(serviceErr restful.ServiceError, request *restful.Request, response *restful.Response) { serviceErrorHandler(s, serviceErr, request, response) }) director := director{ name: name, goRestfulContainer: gorestfulContainer, nonGoRestfulMux: nonGoRestfulMux, } return &APIServerHandler{ // 构建处理器链, 注意传入的director FullHandlerChain: handlerChainBuilder(director), GoRestfulContainer: gorestfulContainer, NonGoRestfulMux: nonGoRestfulMux, Director: director, } } type APIServerHandler struct { // 处理器链,接口是http包中标准的: // type Handler interface { // ServeHTTP(ResponseWriter, *Request) // } // 它组织一系列的过滤器,并在请求通过过滤器链后,调用Director FullHandlerChain http.Handler // 所有注册的API由此容器处理 // InstallAPIs使用该字段,其他server不应该直接访问 GoRestfulContainer *restful.Container // 链中最后一个处理器。这个类型包装一个mux对象,并且记录下注册了哪些URL路径 NonGoRestfulMux *mux.PathRecorderMux // Director用于处理fall through和proxy Director http.Handler } |
这个Handler实现了http.Handler,简单的把请求委托给FullHandlerChain处理:
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func (a *APIServerHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) { a.FullHandlerChain.ServeHTTP(w, r) } |
上面这个函数,就是所有HTTP请求处理的入口点。
FullHandlerChain是handlerChainBuilder()调用得到的:
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var c completedConfig handlerChainBuilder := func(handler http.Handler) http.Handler { return c.BuildHandlerChainFunc(handler, c.Config) } apiServerHandler := NewAPIServerHandler(name, c.Serializer, handlerChainBuilder, delegationTarget.UnprotectedHandler()) |
completedConfig.BuildHandlerChainFunc则来自于它内嵌的Config:
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serverConfig := genericapiserver.NewRecommendedConfig(apiserver.Codecs) func NewRecommendedConfig(codecs serializer.CodecFactory) *RecommendedConfig { return &RecommendedConfig{ Config: *NewConfig(codecs), } } func NewConfig(codecs serializer.CodecFactory) *Config { defaultHealthChecks := []healthz.HealthChecker{healthz.PingHealthz, healthz.LogHealthz} return &Config{ Serializer: codecs, BuildHandlerChainFunc: DefaultBuildHandlerChain, // ... } func DefaultBuildHandlerChain(apiHandler http.Handler, c *Config) http.Handler { // 最内层:传入的apiHandler,也就是上文中的director // 访问控制 handler := genericapifilters.WithAuthorization(apiHandler, c.Authorization.Authorizer, c.Serializer) // 访问速率控制 if c.FlowControl != nil { handler = genericfilters.WithPriorityAndFairness(handler, c.LongRunningFunc, c.FlowControl) } else { handler = genericfilters.WithMaxInFlightLimit(handler, c.MaxRequestsInFlight, c.MaxMutatingRequestsInFlight, c.LongRunningFunc) } // 身份扮演 handler = genericapifilters.WithImpersonation(handler, c.Authorization.Authorizer, c.Serializer) // 审计 handler = genericapifilters.WithAudit(handler, c.AuditBackend, c.AuditPolicyChecker, c.LongRunningFunc) // 处理身份认证失败 failedHandler := genericapifilters.Unauthorized(c.Serializer, c.Authentication.SupportsBasicAuth) failedHandler = genericapifilters.WithFailedAuthenticationAudit(failedHandler, c.AuditBackend, c.AuditPolicyChecker) // 身份验证 handler = genericapifilters.WithAuthentication(handler, c.Authentication.Authenticator, failedHandler, c.Authentication.APIAudiences) // 处理CORS请求 handler = genericfilters.WithCORS(handler, c.CorsAllowedOriginList, nil, nil, nil, "true") // 超时处理 handler = genericfilters.WithTimeoutForNonLongRunningRequests(handler, c.LongRunningFunc, c.RequestTimeout) // 所有长时间运行请求被添加到等待组,用于优雅关机 handler = genericfilters.WithWaitGroup(handler, c.LongRunningFunc, c.HandlerChainWaitGroup) // 将RequestInfo附加到Context对象 handler = genericapifilters.WithRequestInfo(handler, c.RequestInfoResolver) // HTTP Goway处理 if c.SecureServing != nil && !c.SecureServing.DisableHTTP2 && c.GoawayChance > 0 { handler = genericfilters.WithProbabilisticGoaway(handler, c.GoawayChance) } // 设置Cache-Control头为"no-cache, private",因为所有server被authn/authz保护 handler = genericapifilters.WithCacheControl(handler) // 崩溃恢复 handler = genericfilters.WithPanicRecovery(handler) return handler } |
我们可以清楚的看到默认的处理器链包含的大量过滤器,以及处理器是一层层包裹而非链表结构。
最后,我们来从头跟踪一下请求处理过程,首先看看处理器链中的过滤器们:
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func (a *APIServerHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) { a.FullHandlerChain.ServeHTTP(w, r) } // FullHandlerChain是这个类型 type HandlerFunc func(ResponseWriter, *Request) // 巧妙的设计,实现了 // type Handler interface { // ServeHTTP(ResponseWriter, *Request) // } // 接口,但是这个实现,直接委托给类型对应的函数 func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) { f(w, r) } // 进入处理器链的最外层 func withPanicRecovery(handler http.Handler, crashHandler func(http.ResponseWriter, *http.Request, interface{})) http.Handler { handler = httplog.WithLogging(handler, httplog.DefaultStacktracePred) // 处理函数 return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) { defer runtime.HandleCrash(func(err interface{}) { crashHandler(w, req, err) }) // 转发给内层处理器,内层处理器通过闭包捕获 handler.ServeHTTP(w, req) }) } // 省略若干中间的处理器... // 这个处理器值得注意,它将请求信息存放到context中,内层处理器可以直接使用这些信息 // 信息包括: type RequestInfo struct { // 是否针对资源/子资源的请求 IsResourceRequest bool // URL的路径部分 Path string // 小写的HTTP动词 Verb string // API前缀 APIPrefix string // API组 APIGroup string // API版本 APIVersion string // 命名空间 Namespace string // 资源类型名,通常是小写的复数形式,而不是Kind Resource string // 请求的子资源,子资源是scoped to父资源的另外一个资源,可以具有不同的Kind // 例如 /pods对应资源"pods",对应Kind为"Pod" // /pods/foo/status对应资源"pods",对应子资源 "status",对应Kind为"Pod" // 然而 /pods/foo/binding对应资源"pods",对应子资源 "binding", 而对应Kind为"Binding" Subresource string // 对于某些资源,名字是空的。如果请求指示一个名字(不在请求体中)则填写在该字段 // Parts are the path parts for the request, always starting with /{resource}/{name} Parts []string } func WithRequestInfo(handler http.Handler, resolver request.RequestInfoResolver) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) { ctx := req.Context() info, err := resolver.NewRequestInfo(req) if err != nil { responsewriters.InternalError(w, req, fmt.Errorf("failed to create RequestInfo: %v", err)) return } req = req.WithContext(request.WithRequestInfo(ctx, info)) handler.ServeHTTP(w, req) }) } // 省略若干中间的处理器... |
遍历所有过滤器后,来到处理器链的最后一环,也就是director。从名字上可以看到,它在整体上负责请求的分发:
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func (d director) ServeHTTP(w http.ResponseWriter, req *http.Request) { path := req.URL.Path // 遍历已经注册的所有WebService,看看有没有负责当前URL路径的 for _, ws := range d.goRestfulContainer.RegisteredWebServices() { switch { case ws.RootPath() == "/apis": // 如果URL路径是 /apis或/apis/需要特殊处理。通常情况下,应该交由nonGoRestfulMux // 但是在启用descovery的情况下,需要直接由goRestfulContainer处理 if path == "/apis" || path == "/apis/" { klog.V(5).Infof("%v: %v %q satisfied by gorestful with webservice %v", d.name, req.Method, path, ws.RootPath()) d.goRestfulContainer.Dispatch(w, req) return } // 如果前缀匹配 case strings.HasPrefix(path, ws.RootPath()): if len(path) == len(ws.RootPath()) || path[len(ws.RootPath())] == '/' { klog.V(5).Infof("%v: %v %q satisfied by gorestful with webservice %v", d.name, req.Method, path, ws.RootPath()) // don't use servemux here because gorestful servemuxes get messed up when removing webservices // TODO fix gorestful, remove TPRs, or stop using gorestful d.goRestfulContainer.Dispatch(w, req) return } } } // 无法找到匹配,跳过 gorestful 容器 d.nonGoRestfulMux.ServeHTTP(w, req) } |
对于非API资源请求,由PathRecorderMux处理:
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func (m *PathRecorderMux) ServeHTTP(w http.ResponseWriter, r *http.Request) { m.mux.Load().(*pathHandler).ServeHTTP(w, r) } func (h *pathHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) { // pathToHandler 记录了所有精确匹配路径的处理器 // 0 = /healthz/etcd -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 1 = /livez/etcd -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 2 = /metrics -> k8s.io/apiserver/pkg/server/routes.MetricsWithReset.Install.func1 // 3 = /readyz/shutdown -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 4 = /readyz/ping -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 5 = /debug/pprof/profile -> net/http/pprof.Profile // 6 = /healthz/log -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 7 = /livez/log -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 8 = /healthz/ping -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 9 = / -> // 10 = /healthz -> k8s.io/apiserver/pkg/endpoints/metrics.InstrumentHandlerFunc.func1 // 11 = /debug/flags -> k8s.io/apiserver/pkg/server/routes.DebugFlags.Index-fm // 12 = /livez/ping -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 13 = /readyz/log -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 14 = /debug/pprof -> k8s.io/apiserver/pkg/server/routes.redirectTo.func1 // 15 = /debug/pprof/trace -> net/http/pprof.Trace // 16 = /debug/flags/v -> k8s.io/apiserver/pkg/server/routes.StringFlagPutHandler.func1 // 17 = /readyz/poststarthook/start-sample-server-informers -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 18 = /livez/poststarthook/start-sample-server-informers -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 19 = /openapi/v2 -> github.com/NYTimes/gziphandler.NewGzipLevelAndMinSize.func1.1 // 20 = /healthz/poststarthook/start-sample-server-informers -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 21 = /readyz/etcd -> k8s.io/apiserver/pkg/server/healthz.adaptCheckToHandler.func1 // 22 = /index.html -> // 23 = /debug/pprof/symbol -> net/http/pprof.Symbol // 24 = /livez -> k8s.io/apiserver/pkg/endpoints/metrics.InstrumentHandlerFunc.func1 // 25 = /readyz -> k8s.io/apiserver/pkg/endpoints/metrics.InstrumentHandlerFunc.func1 if exactHandler, ok := h.pathToHandler[r.URL.Path]; ok { klog.V(5).Infof("%v: %q satisfied by exact match", h.muxName, r.URL.Path) exactHandler.ServeHTTP(w, r) return } // 前缀匹配路径的处理器,默认有/debug/flags/ 和 /debug/pprof/ for _, prefixHandler := range h.prefixHandlers { if strings.HasPrefix(r.URL.Path, prefixHandler.prefix) { klog.V(5).Infof("%v: %q satisfied by prefix %v", h.muxName, r.URL.Path, prefixHandler.prefix) prefixHandler.handler.ServeHTTP(w, r) return } } // 找不到处理器,404 klog.V(5).Infof("%v: %q satisfied by NotFoundHandler", h.muxName, r.URL.Path) h.notFoundHandler.ServeHTTP(w, r) } |
对于API资源请求,例如路径 /apis/wardle.example.com/v1beta1,则由go-restful处理。go-restful框架内部处理细节我们就忽略了,我们主要深入探讨上文中提到的安装APIGroup,每种资源的go-restful Handler都是由它注册的:
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func (s *GenericAPIServer) InstallAPIGroup(apiGroupInfo *APIGroupInfo) error { return s.InstallAPIGroups(apiGroupInfo) } func (s *GenericAPIServer) InstallAPIGroups(apiGroupInfos ...*APIGroupInfo) error { // 遍历API组 for _, apiGroupInfo := range apiGroupInfos { // 安装API资源 常量 /apis if err := s.installAPIResources(APIGroupPrefix, apiGroupInfo, openAPIModels); err != nil { return fmt.Errorf("unable to install api resources: %v", err) } // setup discovery // Install the version handler. // Add a handler at /apis/<groupName> to enumerate all versions supported by this group. apiVersionsForDiscovery := []metav1.GroupVersionForDiscovery{} for _, groupVersion := range apiGroupInfo.PrioritizedVersions { // Check the config to make sure that we elide versions that don't have any resources if len(apiGroupInfo.VersionedResourcesStorageMap[groupVersion.Version]) == 0 { continue } apiVersionsForDiscovery = append(apiVersionsForDiscovery, metav1.GroupVersionForDiscovery{ GroupVersion: groupVersion.String(), Version: groupVersion.Version, }) } preferredVersionForDiscovery := metav1.GroupVersionForDiscovery{ GroupVersion: apiGroupInfo.PrioritizedVersions[0].String(), Version: apiGroupInfo.PrioritizedVersions[0].Version, } apiGroup := metav1.APIGroup{ Name: apiGroupInfo.PrioritizedVersions[0].Group, Versions: apiVersionsForDiscovery, PreferredVersion: preferredVersionForDiscovery, } s.DiscoveryGroupManager.AddGroup(apiGroup) s.Handler.GoRestfulContainer.Add(discovery.NewAPIGroupHandler(s.Serializer, apiGroup).WebService()) } return nil } // 安装API资源 func (s *GenericAPIServer) installAPIResources(apiPrefix string, apiGroupInfo *APIGroupInfo, openAPIModels openapiproto.Models) error { // 遍历版本 for _, groupVersion := range apiGroupInfo.PrioritizedVersions { // 跳过没有资源的组 if len(apiGroupInfo.VersionedResourcesStorageMap[groupVersion.Version]) == 0 { klog.Warningf("Skipping API %v because it has no resources.", groupVersion) continue } apiGroupVersion := s.getAPIGroupVersion(apiGroupInfo, groupVersion, apiPrefix) if apiGroupInfo.OptionsExternalVersion != nil { apiGroupVersion.OptionsExternalVersion = apiGroupInfo.OptionsExternalVersion } apiGroupVersion.OpenAPIModels = openAPIModels apiGroupVersion.MaxRequestBodyBytes = s.maxRequestBodyBytes // 安装为go-restful的Handler if err := apiGroupVersion.InstallREST(s.Handler.GoRestfulContainer); err != nil { return fmt.Errorf("unable to setup API %v: %v", apiGroupInfo, err) } } return nil } // 注册一系列REST Handler( storage, watch, proxy, redirect)到restful容器 func (g *APIGroupVersion) InstallREST(container *restful.Container) error { // 例如/apis/wardle.example.com/v1beta1 prefix := path.Join(g.Root, g.GroupVersion.Group, g.GroupVersion.Version) installer := &APIInstaller{ group: g, prefix: prefix, minRequestTimeout: g.MinRequestTimeout, } // 执行API资源处理器的安装 apiResources, ws, registrationErrors := installer.Install() // 执行资源发现处理器的安装 versionDiscoveryHandler := discovery.NewAPIVersionHandler(g.Serializer, g.GroupVersion, staticLister{apiResources}) versionDiscoveryHandler.AddToWebService(ws) // 添加WebService到容器 container.Add(ws) return utilerrors.NewAggregate(registrationErrors) } func (a *APIInstaller) Install() ([]metav1.APIResource, *restful.WebService, []error) { var apiResources []metav1.APIResource var errors []error // 创建一个针对特定GV的WebService ws := a.newWebService() // Register the paths in a deterministic (sorted) order to get a deterministic swagger spec. 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 { // 遍历资源,注册处理器,例如flunders apiResource, err := a.registerResourceHandlers(path, a.group.Storage[path], ws) if err != nil { errors = append(errors, fmt.Errorf("error in registering resource: %s, %v", path, err)) } if apiResource != nil { apiResources = append(apiResources, *apiResource) } } return apiResources, ws, errors } func (a *APIInstaller) newWebService() *restful.WebService { ws := new(restful.WebService) // 此WebService的路径模板 ws.Path(a.prefix) // a.prefix contains "prefix/group/version" ws.Doc("API at " + a.prefix) // 向后兼容的考虑,支持没有MIME类型 ws.Consumes("*/*") // 根据API组使用的编解码器来确定响应支持的MIME类型 // 0 = {string} "application/json" // 1 = {string} "application/yaml" // 2 = {string} "application/vnd.kubernetes.protobuf" mediaTypes, streamMediaTypes := negotiation.MediaTypesForSerializer(a.group.Serializer) ws.Produces(append(mediaTypes, streamMediaTypes...)...) // 例如 wardle.example.com/v1beta1 ws.ApiVersion(a.group.GroupVersion.String()) return ws } // 注册资源处理器,过于冗长,仅仅贴片段 func (a *APIInstaller) registerResourceHandlers(path string, storage rest.Storage, ws *restful.WebService) (*metav1.APIResource, error) { // ... // creater就是Handler的核心逻辑所在,它来自rest.Storage,对接Etcd creater, isCreater := storage.(rest.Creater) // ... actions = appendIf(actions, action{"POST", resourcePath, resourceParams, namer, false}, isCreater) switch action.Verb { case "POST": handler = restfulCreateResource(creater, reqScope, admit) route := ws.POST(action.Path).To(handler). Doc(doc). Param(ws.QueryParameter("pretty", "If 'true', then the output is pretty printed.")). Operation("create"+namespaced+kind+strings.Title(subresource)+operationSuffix). Produces(append(storageMeta.ProducesMIMETypes(action.Verb), mediaTypes...)...). Returns(http.StatusOK, "OK", producedObject). // TODO: in some cases, the API may return a v1.Status instead of the versioned object // but currently go-restful can't handle multiple different objects being returned. Returns(http.StatusCreated, "Created", producedObject). Returns(http.StatusAccepted, "Accepted", producedObject). Reads(defaultVersionedObject). Writes(producedObject) if err := AddObjectParams(ws, route, versionedCreateOptions); err != nil { return nil, err } addParams(route, action.Params) routes = append(routes, route) // ... } func restfulCreateResource(r rest.Creater, scope handlers.RequestScope, admit admission.Interface) restful.RouteFunction { return func(req *restful.Request, res *restful.Response) { handlers.CreateResource(r, &scope, admit)(res.ResponseWriter, req.Request) } } func CreateResource(r rest.Creater, scope *RequestScope, admission admission.Interface) http.HandlerFunc { return createHandler(&namedCreaterAdapter{r}, scope, admission, false) } // 创建资源处理器核心 func createHandler(r rest.NamedCreater, scope *RequestScope, admit admission.Interface, includeName bool) http.HandlerFunc { return func(w http.ResponseWriter, req *http.Request) { // For performance tracking purposes. trace := utiltrace.New("Create", utiltrace.Field{Key: "url", Value: req.URL.Path}, utiltrace.Field{Key: "user-agent", Value: &lazyTruncatedUserAgent{req}}, utiltrace.Field{Key: "client", Value: &lazyClientIP{req}}) defer trace.LogIfLong(500 * time.Millisecond) // 处理Dryrun if isDryRun(req.URL) && !utilfeature.DefaultFeatureGate.Enabled(features.DryRun) { scope.err(errors.NewBadRequest("the dryRun feature is disabled"), w, req) return } // TODO: we either want to remove timeout or document it (if we document, move timeout out of this function and declare it in api_installer) timeout := parseTimeout(req.URL.Query().Get("timeout")) // 命名空间和资源名字处理 namespace, name, err := scope.Namer.Name(req) if err != nil { if includeName { // name was required, return scope.err(err, w, req) return } // otherwise attempt to look up the namespace namespace, err = scope.Namer.Namespace(req) if err != nil { scope.err(err, w, req) return } } ctx, cancel := context.WithTimeout(req.Context(), timeout) defer cancel() ctx = request.WithNamespace(ctx, namespace) // 协商输出MIME类型 outputMediaType, _, err := negotiation.NegotiateOutputMediaType(req, scope.Serializer, scope) if err != nil { scope.err(err, w, req) return } gv := scope.Kind.GroupVersion() // 协商输入如何反串行化 s, err := negotiation.NegotiateInputSerializer(req, false, scope.Serializer) if err != nil { scope.err(err, w, req) return } // 从串行化器得到能将请求解码为特定版本的解码器 decoder := scope.Serializer.DecoderToVersion(s.Serializer, scope.HubGroupVersion) // 读取请求体 body, err := limitedReadBody(req, scope.MaxRequestBodyBytes) if err != nil { scope.err(err, w, req) return } options := &metav1.CreateOptions{} values := req.URL.Query() if err := metainternalversionscheme.ParameterCodec.DecodeParameters(values, scope.MetaGroupVersion, options); err != nil { err = errors.NewBadRequest(err.Error()) scope.err(err, w, req) return } if errs := validation.ValidateCreateOptions(options); len(errs) > 0 { err := errors.NewInvalid(schema.GroupKind{Group: metav1.GroupName, Kind: "CreateOptions"}, "", errs) scope.err(err, w, req) return } options.TypeMeta.SetGroupVersionKind(metav1.SchemeGroupVersion.WithKind("CreateOptions")) defaultGVK := scope.Kind // 实例化资源的Go结构 original := r.New() trace.Step("About to convert to expected version") // 将请求体解码到Go结构中 obj, gvk, err := decoder.Decode(body, &defaultGVK, original) if err != nil { err = transformDecodeError(scope.Typer, err, original, gvk, body) scope.err(err, w, req) return } if gvk.GroupVersion() != gv { err = errors.NewBadRequest(fmt.Sprintf("the API version in the data (%s) does not match the expected API version (%v)", gvk.GroupVersion().String(), gv.String())) scope.err(err, w, req) return } trace.Step("Conversion done") // 审计和Admission控制 ae := request.AuditEventFrom(ctx) admit = admission.WithAudit(admit, ae) audit.LogRequestObject(ae, obj, scope.Resource, scope.Subresource, scope.Serializer) userInfo, _ := request.UserFrom(ctx) // On create, get name from new object if unset if len(name) == 0 { _, name, _ = scope.Namer.ObjectName(obj) } trace.Step("About to store object in database") admissionAttributes := admission.NewAttributesRecord(obj, nil, scope.Kind, namespace, name, scope.Resource, scope.Subresource, admission.Create, options, dryrun.IsDryRun(options.DryRun), userInfo) // 构建入库函数 requestFunc := func() (runtime.Object, error) { // 调用rest.Storage进行入库 return r.Create( ctx, name, obj, rest.AdmissionToValidateObjectFunc(admit, admissionAttributes, scope), options, ) } // finishRequest能够异步执行回调,并且处理响应返回的错误 result, err := finishRequest(timeout, func() (runtime.Object, error) { if scope.FieldManager != nil { liveObj, err := scope.Creater.New(scope.Kind) if err != nil { return nil, fmt.Errorf("failed to create new object (Create for %v): %v", scope.Kind, err) } obj = scope.FieldManager.UpdateNoErrors(liveObj, obj, managerOrUserAgent(options.FieldManager, req.UserAgent())) } if mutatingAdmission, ok := admit.(admission.MutationInterface); ok && mutatingAdmission.Handles(admission.Create) { if err := mutatingAdmission.Admit(ctx, admissionAttributes, scope); err != nil { return nil, err } } result, err := requestFunc() // If the object wasn't committed to storage because it's serialized size was too large, // it is safe to remove managedFields (which can be large) and try again. if isTooLargeError(err) { if accessor, accessorErr := meta.Accessor(obj); accessorErr == nil { accessor.SetManagedFields(nil) result, err = requestFunc() } } return result, err }) if err != nil { scope.err(err, w, req) return } trace.Step("Object stored in database") code := http.StatusCreated status, ok := result.(*metav1.Status) if ok && err == nil && status.Code == 0 { status.Code = int32(code) } transformResponseObject(ctx, scope, trace, req, w, code, outputMediaType, result) } } |
回顾一下请求处理的整体逻辑:
- GenericAPIServer.Handler就是http.Handler,可以注册给任何HTTP服务器。因此我们想绕开HTTPS的限制应该很容易
- GenericAPIServer.Handler是一个层层包裹的处理器链,外层是一系列过滤器,最里面是director
- director负责整体的请求分发:
- 对于非API资源请求,分发给nonGoRestfulMux。我们可以利用这个扩展点,扩展任意形式的HTTP接口
- 对于API资源请求,分发给gorestfulContainer
- 在GenericAPIServer.InstallAPIGroup中,所有支持的API资源的所有版本,都注册为go-restful的一个WebService
- 这些WebService的逻辑包括(依赖于rest.Storage):
- 将请求解码为资源对应的Go结构
- 将Go结构编码为JSON
- 将JSON存储到Etcd
通过对sample-apiserver的代码分析,我们理解了构建自己的API Server的各种关键要素。
APIServer的核心类型是 GenericAPIServer,它是由 genericapiserver.CompletedConfig的 New()方法生成的。后者则是 genericapiserver.RecommendedConfig的 Complete()方法生成的。而RecommendedConfig又是从 genericoptions.RecommendedOptions得到的。sample-apiserver对Config、Option、Server等对象都做了一层包装,我们不关注这些wrapper。
RecommendedOptions对应了用户提供的各类选项(外加所谓推荐选项,降低使用时的复杂度),例如Etcd地址、Etcd存储前缀、APIServer的基本信息等等。调用RecommendedOptions的 ApplyTo方法,会根据选项,推导出APIServer所需的,完整的配置信息。在这个方法中,甚至会进行自签名证书等重操作,而不是简单的将信息从Option复制给Config。RecommendedOptions会依次调用它的各个字段的ApplyTo方法,从而推导出RecommendedConfig的各个字段。
RecommendedConfig的Complete方法,再一次进行配置信息的推导,主要牵涉到OpenAPI相关的配置。
CompletedConfig的New方法实例化GenericAPIServer,这一步最关键的逻辑是安装API组。API组定义了如何实现GroupVersion中API的增删改查,它将GroupVersion的每种资源映射到registry.REST,后者具有处理REST风格请求的能力,并(默认)存储到Etcd。
GenericAPIServer提供了一些钩子来处理Admission控制器的注册、初始化。以及另外一些钩子来对API Server的生命周期事件做出响应。
想实现sample-apiserver的独立运行,RecommendedOptions有三个字段必须处理:Authentication、Authorization、CoreAPI,它们都隐含了对主kube-apiserver的依赖。
Authentication依赖主kube-apiserver,是因为它需要访问TokenReviewInterface,访问kube-system中的ConfigMap。Authorization依赖主kube-apiserver,是因为它需要访问SubjectAccessReviewInterface。CoreAPI则是直接为Config提供了两个字段:ClientConfig、SharedInformerFactory。
将这些字段置空,可以解除对主kube-apiserver的依赖。这样启动sample-apiserver时就不需要提供这三个命令行选项:
--kubeconfig=/home/alex/.kube/config
--authentication-kubeconfig=/home/alex/.kube/config
--authorization-kubeconfig=/home/alex/.kube/config
但是,置空CoreAPI会导致报错:admission depends on a Kubernetes core API shared informer, it cannot be nil。这提示我们不能在不依赖主kube-apiserver的情况下使用Admission控制器这一特性,需要将Admission也置空:
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o.RecommendedOptions.Authentication = nil o.RecommendedOptions.Authorization = nil o.RecommendedOptions.CoreAPI = nil o.RecommendedOptions.Admission = nil |
清空上述四个字段后,sample-server还会在PostStart钩子中崩溃:
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// panic,这个SharedInformerFactory是CoreAPI选项提供的 config.GenericConfig.SharedInformerFactory.Start(context.StopCh) // 仅仅Admission控制器使用该InformerFactory o.SharedInformerFactory.Start(context.StopCh) |
由于注释中给出的原因,这个PostStart钩子已经没有意义,删除即可正常启动服务器。
GenericAPIServer的 Run方法的默认实现,是调用 s.SecureServingInfo.Serve,因而强制使用HTTPS:
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stoppedCh, err = s.SecureServingInfo.Serve(s.Handler, s.ShutdownTimeout, internalStopCh) |
不过,很明显的,我们只需要将s.Handler传递给自己的http.Server即可使用HTTP。
我们的迁移工具还提供一些非Kubernetes风格的HTTP接口,那么如何集成到APIServer中呢?
在启动服务器之前,可以直接访问 GenericAPIServer.Handler.NonGoRestfulMux,NonGoRestfulMux实现了:
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type mux interface { Handle(pattern string, handler http.Handler) } |
调用Handle即可为任何路径注册处理器。
通过对sample-apiserver代码的分析,我们了解到构建自己的API Server有大量繁琐的工作需要做。幸运的是,K8S提供了apiserver-builder-alpha简化这一过程。
apiserver-builder-alpha是一系列工具和库的集合,它能够:
- 为新的API资源创建Go类型、控制器(基于controller-runtime)、测试用例、文档
- 构建、(独立、在Minikube或者在K8S中)运行扩展的控制平面组件(APIServer)
- 让在控制器中watch/update资源更简单
- 让创建新的资源/子资源更简单
- 提供大部分合理的默认值
下载压缩包,解压并存放到目录,然后设置环境变量:
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export PATH=$HOME/.local/kubernetes/apiserver-builder/bin/:$PATH |
你需要在$GOPATH下创建一个项目,创建一个boilerplate.go.txt文件。然后执行:
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apiserver-boot init repo --domain cloud.gmem.cc |
该命令会生成如下目录结构:
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. ├── bin ├── boilerplate.go.txt ├── BUILD.bazel ├── cmd │ ├── apiserver │ │ └── main.go │ └── manager │ └── main.go ├── go.mod ├── go.sum ├── pkg │ ├── apis │ │ └── doc.go │ ├── controller │ │ └── doc.go │ ├── doc.go │ ├── openapi │ │ └── doc.go │ └── webhook │ └── webhook.go ├── PROJECT └── WORKSPAC |
cmd/apiserver/main.go,是APIServer的入口点:
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import "sigs.k8s.io/apiserver-builder-alpha/pkg/cmd/server" func main() { version := "v0" err := server.StartApiServerWithOptions(&server.StartOptions{ EtcdPath: "/registry/cloud.gmem.cc", // 无法运行,这个函数不存在 Apis: apis.GetAllApiBuilders(), Openapidefs: openapi.GetOpenAPIDefinitions, Title: "Api", Version: version, // TweakConfigFuncs []func(apiServer *apiserver.Config) error // FlagConfigFuncs []func(*cobra.Command) error }) if err != nil { panic(err) } } |
可以看到apiserver-builder-alpha进行了一些封装。
执行下面的命令,添加一个新的API资源:
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apiserver-boot create group version resource --group tcm --version v1 --kind Flunder |
最后,执行命令可以在本地启动APIServer:
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apiserver-boot run local |
本文提及的工具项目,最初架构是基于CRD,使用kubebuilder进行代码生成。kubebuilder的目录结构和apiserver-builder并不兼容。
此外apiserver-builder项目仍然处于Alpha阶段,并且经过测试,发现生成代码无法运行。为了避免不必要的麻烦,我们不打算使用它。
由于apiserver-builder不成熟,而且我们已经基于kubebuilder完成了大部分开发工作。因此打算基于分析sample-apiserver获得的经验,手工编写一个独立运行、使用HTTP协议的APIServer。
kubebuilder并不会生成zz_generated.openapi.go文件,因为该文件对于CRD没有意义。但是这个文件对于独立API Server是必须的。
我们需要为资源类型所在包添加注解:
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// +k8s:openapi-gen=true package v1 |
并调用openapi-gen生成此文件:
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openapi-gen \ --input-dirs "k8s.io/apimachinery/pkg/apis/meta/v1,k8s.io/apimachinery/pkg/runtime,k8s.io/apimachinery/pkg/version" \ --input-dirs cloud.gmem.cc/teleport/api/v1 -p cloud.gmem.cc/teleport/api/v1 -O zz_generated.openapi |
下面是完整的quick&dirty的代码:
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package main import ( v1 "cloud.gmem.cc/teleport/api/v1" "context" "fmt" metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" "k8s.io/apimachinery/pkg/fields" "k8s.io/apimachinery/pkg/labels" "k8s.io/apimachinery/pkg/runtime" "k8s.io/apimachinery/pkg/runtime/schema" "k8s.io/apimachinery/pkg/runtime/serializer" utilruntime "k8s.io/apimachinery/pkg/util/runtime" "k8s.io/apimachinery/pkg/util/validation/field" "k8s.io/apiserver/pkg/endpoints/openapi" "k8s.io/apiserver/pkg/features" "k8s.io/apiserver/pkg/registry/generic" genericregistry "k8s.io/apiserver/pkg/registry/generic/registry" "k8s.io/apiserver/pkg/registry/rest" genericapiserver "k8s.io/apiserver/pkg/server" genericoptions "k8s.io/apiserver/pkg/server/options" "k8s.io/apiserver/pkg/storage" "k8s.io/apiserver/pkg/storage/names" "k8s.io/apiserver/pkg/util/feature" utilfeature "k8s.io/apiserver/pkg/util/feature" "net" "net/http" "os" "reflect" ctrl "sigs.k8s.io/controller-runtime" ) var ( setupLog = ctrl.Log.WithName("setup") ) func main() { s := runtime.NewScheme() utilruntime.Must(v1.AddToScheme(s)) gv := v1.GroupVersion utilruntime.Must(s.SetVersionPriority(gv)) metav1.AddToGroupVersion(s, schema.GroupVersion{Version: "v1"}) unversioned := schema.GroupVersion{Group: "", Version: "v1"} s.AddUnversionedTypes(unversioned, &metav1.Status{}, &metav1.APIVersions{}, &metav1.APIGroupList{}, &metav1.APIGroup{}, &metav1.APIResourceList{}, ) // 必须注册一个__internal版本,否则报错 // failed to prepare current and previous objects: no kind "Flunder" is registered for the internal version of group "tcm.cloud.gmem.cc" in scheme gvi := gv gvi.Version = runtime.APIVersionInternal s.AddKnownTypes(gvi, &v1.Flunder{}, &v1.FlunderList{}) codecFactory := serializer.NewCodecFactory(s) codec := codecFactory.LegacyCodec(gv) options := genericoptions.NewRecommendedOptions( "/teleport/cloud.gmem.cc", codec, ) options.Etcd.StorageConfig.EncodeVersioner = runtime.NewMultiGroupVersioner(gv, schema.GroupKind{Group: gv.Group}) ips := []net.IP{net.ParseIP("127.0.0.1")} if err := options.SecureServing.MaybeDefaultWithSelfSignedCerts("localhost", nil, ips); err != nil { setupLog.Error(err, "error creating self-signed certificates") os.Exit(1) } options.Etcd.StorageConfig.Paging = utilfeature.DefaultFeatureGate.Enabled(features.APIListChunking) options.Etcd.StorageConfig.Transport.ServerList = []string{"http://etcd.gmem.cc:2379"} options.Authentication = nil options.Authorization = nil options.CoreAPI = nil options.Admission = nil options.SecureServing.BindPort = 6443 config := genericapiserver.NewRecommendedConfig(codecFactory) config.OpenAPIConfig = genericapiserver.DefaultOpenAPIConfig(v1.GetOpenAPIDefinitions, openapi.NewDefinitionNamer(s)) config.OpenAPIConfig.Info.Title = "Teleport" config.OpenAPIConfig.Info.Version = "1.0" feature.DefaultMutableFeatureGate.SetFromMap(map[string]bool{ string(features.APIPriorityAndFairness): false, }) if err := options.ApplyTo(config); err != nil { panic(err) } completedConfig := config.Complete() server, err := completedConfig.New("teleport-apiserver", genericapiserver.NewEmptyDelegate()) if err != nil { panic(err) } apiGroupInfo := genericapiserver.NewDefaultAPIGroupInfo(gv.Group, s, metav1.ParameterCodec, codecFactory) v1storage := map[string]rest.Storage{} resource := v1.ResourceFlunders v1storage[resource] = createStore( s, gv.WithResource(resource).GroupResource(), func() runtime.Object { return &v1.Flunder{} }, func() runtime.Object { return &v1.FlunderList{} }, completedConfig.RESTOptionsGetter, ) apiGroupInfo.VersionedResourcesStorageMap[gv.Version] = v1storage if err := server.InstallAPIGroups(&apiGroupInfo); err != nil { panic(err) } server.AddPostStartHookOrDie("teleport-post-start", func(context genericapiserver.PostStartHookContext) error { return nil }) preparedServer := server.PrepareRun() http.ListenAndServe(":6080", preparedServer.Handler) } func createStore(scheme *runtime.Scheme, gr schema.GroupResource, newFunc, newListFunc func() runtime.Object, optsGetter generic.RESTOptionsGetter) rest.Storage { attrs := func(obj runtime.Object) (labels.Set, fields.Set, error) { typ := reflect.TypeOf(newFunc()) if reflect.TypeOf(obj) != typ { return nil, nil, fmt.Errorf("given object is not a %s", typ.Name()) } oma := obj.(metav1.ObjectMetaAccessor) meta := oma.GetObjectMeta() return meta.GetLabels(), fields.Set{ "metadata.name": meta.GetName(), "metadata.namespace": meta.GetNamespace(), }, nil } s := strategy{ scheme, names.SimpleNameGenerator, } store := &genericregistry.Store{ NewFunc: newFunc, NewListFunc: newListFunc, PredicateFunc: func(label labels.Selector, field fields.Selector) storage.SelectionPredicate { return storage.SelectionPredicate{ Label: label, Field: field, GetAttrs: attrs, } }, DefaultQualifiedResource: gr, CreateStrategy: s, UpdateStrategy: s, DeleteStrategy: s, TableConvertor: rest.NewDefaultTableConvertor(gr), } options := &generic.StoreOptions{RESTOptions: optsGetter, AttrFunc: attrs} if err := store.CompleteWithOptions(options); err != nil { panic(err) } return store } type strategy struct { runtime.ObjectTyper names.NameGenerator } func (strategy) NamespaceScoped() bool { return true } func (strategy) PrepareForCreate(ctx context.Context, obj runtime.Object) { } func (strategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object) { } func (strategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList { return field.ErrorList{} } func (strategy) AllowCreateOnUpdate() bool { return false } func (strategy) AllowUnconditionalUpdate() bool { return false } func (strategy) Canonicalize(obj runtime.Object) { } func (strategy) ValidateUpdate(ctx context.Context, obj, old runtime.Object) field.ErrorList { return field.ErrorList{} } |
在安装APIGroup的时候,我们需要为每API组的每个版本的每种资源,指定存储后端:
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// 每个组 apiGroupInfo := genericapiserver.NewDefaultAPIGroupInfo(wardle.GroupName, Scheme, metav1.ParameterCodec, Codecs) // 每个版本 v1alpha1storage := map[stcongring]rest.Storage{} // 每种资源提供一个rest.Storage v1alpha1storage["flunders"] = wardleregistry.RESTInPeace(flunderstorage.NewREST(Scheme, c.GenericConfig.RESTOptionsGetter)) // 安装APIGroup s.GenericAPIServer.InstallAPIGroup(&apiGroupInfo) |
默认情况下,使用的是genericregistry.Store,它对接到Etcd。要实现自己的存储后端,实现相关接口即可。
注意:关于存储后端,有很多细节需要处理。
下面贴一个在文件系统中,以YAML形式存储API资源的例子:
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package file import ( "bytes" "context" |