【K8s源码品读】007：Phase 1 - kube-apiserver - Pod数据的保存

聚焦目标

理解Pod发送到kube-apiserver后是怎么保存的

目录

1. RESTCreateStrategy创建的预处理
2. REST Pod数据的存储
3. 存储的底层实现
4. kube-apiserver第一阶段源码阅读总结

RESTCreateStrategy

// podStrategy 是封装了 Pod 的各类动作，这里我们先关注create这个操作
type podStrategy struct {
   
    runtime.ObjectTyper
    names.NameGenerator
}

// podStrategy 的接口
type RESTCreateStrategy interface {
   
    runtime.ObjectTyper
    names.NameGenerator
  // 是否属于当前的 namespace
    NamespaceScoped() bool
  // 准备创建前的检查
    PrepareForCreate(ctx context.Context, obj runtime.Object)
  // 验证资源对象
    Validate(ctx context.Context, obj runtime.Object) field.ErrorList
  // 规范化
    Canonicalize(obj runtime.Object)
}

// 完成了检查，我们就要保存数据了

Storage

// PodStorage 是 Pod 存储的实现，里面包含了多个存储的定义
type PodStorage struct {
   
  // REST implements a RESTStorage for pods
    Pod                 *REST
  // BindingREST implements the REST endpoint for binding pods to nodes when etcd is in use.
    Binding             *BindingREST
  // LegacyBindingREST implements the REST endpoint for binding pods to nodes when etcd is in use.
    LegacyBinding       *LegacyBindingREST
    Eviction            *EvictionREST
  // StatusREST implements the REST endpoint for changing the status of a pod.
    Status              *StatusREST
  // EphemeralContainersREST implements the REST endpoint for adding EphemeralContainers
    EphemeralContainers *EphemeralContainersREST
    Log                 *podrest.LogREST
    Proxy               *podrest.ProxyREST
    Exec                *podrest.ExecREST
    Attach              *podrest.AttachREST
    PortForward         *podrest.PortForwardREST
}

/*
从上一节的map关系中，保存在REST中
restStorageMap := map[string]rest.Storage{
        "pods":             podStorage.Pod,
}
*/
type REST struct {
   
    *genericregistry.Store
    proxyTransport http.RoundTripper
}

// Store是一个通用的数据结构
type Store struct {
   
    // Storage定义
    Storage DryRunnableStorage
}

// DryRunnableStorage中的Storage是一个Interface
type DryRunnableStorage struct {
   
    Storage storage.Interface
    Codec   runtime.Codec
}

func (s *DryRunnableStorage) Create(ctx context.Context, key string, obj, out runtime.Object, ttl uint64, dryRun bool) error {
   
    if dryRun {
   
        if err := s.Storage.Get(ctx, key, storage.GetOptions{
   }, out); err == nil {
   
            return storage.NewKeyExistsError(key, 0)
        }
        return s.copyInto(obj, out)
    }
  // 这里，就是Create的真正调用
    return s.Storage.Create(ctx, key, obj, out, ttl)
}

Storage Implement

// Storage Interface 的定义，包括基本的增删改查，以及watch等等进阶操作
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, opts ListOptions) (watch.Interface, error)
    WatchList(ctx context.Context, key string, opts ListOptions) (watch.Interface, error)
    Get(ctx context.Context, key string, opts GetOptions, objPtr runtime.Object) error
    GetToList(ctx context.Context, key string, opts ListOptions, listObj runtime.Object) error
    List(ctx context.Context, key string, opts ListOptions, 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)
}

func NewRawStorage(config *storagebackend.Config) (storage.Interface, factory.DestroyFunc, error) {
   
    return factory.Create(*config)
}

func Create(c storagebackend.Config) (storage.Interface, DestroyFunc, error) {
   
    switch c.Type {
   
  // 已经不支持etcd2
    case "etcd2":
        return nil, nil, fmt.Errorf("%v is no longer a supported storage backend", c.Type)
  // 默认为etcd3版本
    case storagebackend.StorageTypeUnset, storagebackend.StorageTypeETCD3:
        return newETCD3Storage(c)
    default:
        return nil, nil, fmt.Errorf("unknown storage type: %s", c.Type)
    }
}

Summary

我们对第一阶段学习kube-apiserver的知识点进行总结：

1. kube-apiserver 包含三个apiserverAPIExtensionsServer、KubeAPIServer和AggregatorServer
   1. 三个APIServer底层均依赖通用的GenericServer，使用go-restful对外提供RESTful风格的API服务
2. kube-apiserver 对请求进行 Authentication、Authorization和Admission三层验证
3. 完成验证后，请求会根据路由规则，触发到对应资源的handler，主要包括数据的预处理和保存
4. kube-apiserver 的底层存储为etcd v3，它被抽象为一种RESTStorage，使请求和存储操作一一对应