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作者：weixin_34037977
来源：CSDN
原文：https://blog.csdn.net/weixin_34037977/article/details/87058105
在Kubernetes源码分析-- API Server之API Install篇中，我们了解到K8S可以支持多版本的API，但是Rest API的不同版本中接口的输入输出参数的格式是有差别的，Kubernetes是怎么处理这个问题的呢？另外Kubernetes支持yaml、json两个格式的配置，同时又能够支持json、yaml和pb等格式的编解码进行协议传输，那么Kubernetes又是如何实现各种数据对象的序列化、反序列化的呢？
runtime.Scheme
为了同时解决数据对象的序列化、反序列化与多版本数据对象的兼容和转换问题，Kubernetes设计了一套复杂的机制，首先，它设计了runtime.Scheme这个结构体(k8s.io/apimachinery/pkg/runtime/schema.go)，以下是对它的定义。
// Scheme defines methods for serializing and deserializing API objects, a type
// registry for converting group, version, and kind information to and from Go
// schemas, and mappings between Go schemas of different versions. A scheme is the
// foundation for a versioned API and versioned configuration over time.
//
// In a Scheme, a Type is a particular Go struct, a Version is a point-in-time
// identifier for a particular representation of that Type (typically backwards
// compatible), a Kind is the unique name for that Type within the Version, and a
// Group identifies a set of Versions, Kinds, and Types that evolve over time. An
// Unversioned Type is one that is not yet formally bound to a type and is promised
// to be backwards compatible (effectively a "v1" of a Type that does not expect
// to break in the future).
//
// Schemes are not expected to change at runtime and are only threadsafe after
// registration is complete.
type Scheme struct {
// versionMap allows one to figure out the go type of an object with
// the given version and name.
gvkToType map[schema.GroupVersionKind]reflect.Type
// typeToGroupVersion allows one to find metadata for a given go object.
// The reflect.Type we index by should *not* be a pointer.
typeToGVK map[reflect.Type][]schema.GroupVersionKind
// unversionedTypes are transformed without conversion in ConvertToVersion.
unversionedTypes map[reflect.Type]schema.GroupVersionKind
// unversionedKinds are the names of kinds that can be created in the context of any group
// or version
// TODO: resolve the status of unversioned types.
unversionedKinds map[string]reflect.Type
// Map from version and resource to the corresponding func to convert
// resource field labels in that version to internal version.
fieldLabelConversionFuncs map[schema.GroupVersionKind]FieldLabelConversionFunc
// defaulterFuncs is an array of interfaces to be called with an object to provide defaulting
// the provided object must be a pointer.
defaulterFuncs map[reflect.Type]func(interface{})
// converter stores all registered conversion functions. It also has
// default converting behavior.
converter *conversion.Converter
// versionPriority is a map of groups to ordered lists of versions for those groups indicating the
// default priorities of these versions as registered in the scheme
versionPriority map[string][]string
// observedVersions keeps track of the order we‘ve seen versions during type registration
observedVersions []schema.GroupVersion
// schemeName is the name of this scheme. If you don‘t specify a name, the stack of the NewScheme caller will be used.
// This is useful for error reporting to indicate the origin of the scheme.
schemeName string
}
runtime.Scheme是带版本的API与带版本的配置文件的基础。
runtime.Scheme定义了以下内容：
序列化和反序列化API对象的方法
类型登记处：用于在不同版本的Go shemas之间转换group 、version和kind信息
从上述代码中可以看到，typeToGVK与gkvToType属性就是为了解决数据对象的序列化与反序列化问题，converter属性则负责不同版本的数据对象转换问题；unversionedKind用于映射哪些能够在任意group和version情况下的类型，key是一个string，也就是kind；fieldLabelConversionFuncs：用于解决数据对象的属性名称的兼容性转换和检验，比如讲需要兼容Pod的spec.Host属性改为spec.nodeName的情况。
Kubernetes这个设计思路简单方便地建解决多版本的序列化和数据转换问题，下面是runtime.Scheme里序列化、反序列化的核心方法New()的代码：通过查找gkvToType里匹配的诸多类型，以反射方法生成一个空的数据对象：
// New returns a new API object of the given version and name, or an error if it hasn‘t
// been registered. The version and kind fields must be specified.
func (s *Scheme) New(kind schema.GroupVersionKind) (Object, error) {
if t, exists := s.gvkToType[kind]; exists {
return reflect.New(t).Interface().(Object), nil
}
if t, exists := s.unversionedKinds[kind.Kind]; exists {
return reflect.New(t).Interface().(Object), nil
}
return nil, NewNotRegisteredErrForKind(s.schemeName, kind)
}
由于这个方法的实现，也让Scheme实现了ObjectCreater接口。
注意到runtime.Scheme只是实现了一个序列化与类型转换的框架API，提供了注册资源数据类型与转换函数的功能，那么具体的资源数据对象、转换函数又是在哪个包里实现的呢？答案是k8s.io/api/{resource}/{version}/register.go，而核心资源在k8s.io/api/core/v1/register.go中完成注册，以核心资源为例说明一下目录下的关键的代码
types.go：k8s.io/api/core/v1/types.go
定义了Rest API接口中设计的所有核心的数据类型
register.go 负责将types.go里定义的数据类型注册到runtime.Scheme里。
在register.go中，我们看到这里可以看到两个定义：
var ( // TODO: move SchemeBuilder with zz_generated.deepcopy.go to k8s.io/api. // localSchemeBuilder and AddToScheme will stay in k8s.io/kubernetes. SchemeBuilder = runtime.NewSchemeBuilder(addKnownTypes) localSchemeBuilder = &SchemeBuilder AddToScheme = localSchemeBuilder.AddToScheme )
但是只提供了注册的方法，其实还没有执行注册的过程。什么时候执行这个过程呢？
待抄。。。
明天继续。。。
原文地址：https://www.cnblogs.com/waken-captain/p/10560862.html