FoghostCn commented on issue #2432:
URL: https://github.com/apache/dubbo-go/issues/2432#issuecomment-1786377625
# Metadata模块优化 draft
- MetadataService 本地及对外暴露元数据接口
```go
// 从 ServiceDiscovery 列表中获取元数据信息
type MetadataService interface {
// 服务段暴露的接口 url
GetExportedServiceURLs() ([]*common.URL, error)
// 客户端订阅的接口 url
GetSubscribedURLs() ([]*common.URL, error)
// metadata 版本号
Version() (string, error)
// 获取本地服务发现的 metadataInfo，用于对外暴露，客户端可以通过这个接口获取应用 metadataInfo
GetMetadataInfo(revision string) (*MetadataInfo, error)
// 获取本地所有的服务发现的 metadataInfo 列表
getMetadataInfos()[]*MetadataInfo
// 获取 metadataService 服务的 url 参数
GetMetadataServiceURL() (*common.URL, error)
}
```
- MetadataInfo 存储 servicediscovery 相关元数据容器
```go
type MetadataInfo struct {
Reported bool `json:"-"`
App string `json:"app,omitempty"`
Revision string
`json:"revision,omitempty"`
Services map[string]*ServiceInfo
`json:"services,omitempty"`
exportedServiceURLs map[string]gxset.HashSet
subscribedServiceURLs map[string]gxset.HashSet
}
// 服务端 添加一个service 的 url，一个应用可以有多个服务暴露，一个接口可以有多个协议暴露
func (info *MetadataInfo) AddService(url *common.URL) (bool, error) {
}
// 服务端 删除一个 service 的 url 元数据
func (info *MetadataInfo) RemoveService(url *common.URL) error {
}
// 客户端 订阅一个 服务的 url 元数据
func (info *MetadataInfo) AddSubscribeURL(url *common.URL) (bool, error) {
}
// 客户端 删除一个订阅的服务 url 元数据
func (info *MetadataInfo) RemoveSubscribeURL(url *common.URL) error{
}
```
- ServiceDiscovery 的 metadata 接口
```go
// register/subscribe 时将元数据写入自身 metadataInfo，
// unregister/unsubscribe 时移除 metadataInfo 中相关内容
type ServiceDiscovery interface {
// 返回本地服务元数据
GetLocalMetadata() *MetadataInfo;
// 从本地缓存获取，否则从 MetadataReport 获取，否则从 rpc MetadataService 获取
GetRemoteMetadata(revision string) *MetadataInfo
}
```
- MetadataReport 接口
```go
// 接口均为应用级服务发现使用
type MetadataReport interface {
// GetAppMetadata get metadata info from report
// zookeeper: /dubbo/metadata/dubbo.io/${revision}
GetAppMetadata(*identifier.SubscriberMetadataIdentifier)
(*MetadataInfo, error)
// PublishAppMetadata publish metadata info to reportss
// zookeeper: /dubbo/metadata/dubbo.io/${revision}
PublishAppMetadata(*identifier.SubscriberMetadataIdentifier,
*MetadataInfo) error
// RegisterServiceAppMapping map the specified Dubbo service interface
to current Dubbo app name
// zookeeper:
/dubbo/mapping/org.apache.dubbo.samples.api.GreetingsService
RegisterServiceAppMapping(key string, group string, content string)
error
// GetServiceAppMapping get the app names from the specified Dubbo
service interface
// zookeeper:
/dubbo/mapping/org.apache.dubbo.samples.api.GreetingsService
GetServiceAppMapping(key string, group string, MappingListener)
(*gxset.HashSet, error)
// RemoveServiceAppMappingListener remove the serviceMapping listener
by key and group
// zookeeper:
/dubbo/mapping/org.apache.dubbo.samples.api.GreetingsService
RemoveServiceAppMappingListener(key string, group string) error
}
```
- 元数据中心数据维护流程
```go
Server:
start -> export -> register -> PublishAppMetadata &&
RegisterServiceAppMapping
Client:
start -> refer -> subscribe -> GetServiceAppMapping && GetAppMetadata
->
stop -> unsubscribe -> RemoveServiceAppMappingListener
```
- 目录调整：
```
common
├── extension
│ ├── metadata_remote.go // 取消扩展接口，操作远程 Metadata
│ ├── metadata_report_factory.go
│ ├── metadata_service.go // 取消扩展接口， MetadataService 本身
│ ├── metadata_service_exporter.go // 取消扩展接口 MetadataService 暴露方式
│ ├── metadata_service_proxy_factory.go // 取消扩展接口，rpc 调用 MetadataService
├── metadata_info.go // move to metadata 目录
config
├── instance // move to metadata 目录
│ ├── metadata_report.go // MetadataReport 实例化，全局缓存
│ ├── registry_metadata_report.go // registry 相关 MetadataReport 缓存
├── metadata_report_config.go // 配置相关实体
metadata
├── definition // 删除，不再需要
│ ├── definition.go // 实体定义 provider metadata
│ └── mock.go
├── identifier // move to metadata/report metadataReport 接口参数定义
│ ├── base_metadata_identifier.go
│ ├── metadata_identifier.go
│ ├── service_metadata_identifier.go
│ ├── subscribe_metadata_identifier.go
├── mapping
│ ├── memory
│ │ └── service_name_mapping.go
│ ├── metadata
│ │ └── service_name_mapping.go
│ ├── mock_service_name_mapping.go
│ └── service_name_mapping.go
├── report // MetadataReport 各种实现
│ ├── delegate
│ │ ├── delegate_report.go
│ ├── etcd
│ │ ├── report.go
│ ├── factory
│ │ └── report_factory.go
│ ├── nacos
│ │ ├── report.go
│ ├── report.go
│ ├── reporter_metric.go
│ └── zookeeper
│ └── report.go
└── service // 整体上移到 metadata 目录
├── exporter // MetadataService export as service
│ ├── configurable
│ │ ├── exporter.go
│ └── exporter.go // MetadataService 暴露接口定义，可扩展自定义实现？
├── local
│ ├── metadata_service_proxy_factory.go
│ ├── service.go
│ ├── service_proxy.go // rpc 获取 metadataInfo，可以简化实现，
│── service_test.go
├── local_service.go
├── remote
│ ├── service.go
└── remote_service.go // 应用级服务发现使用
```
- 调整后目录：
```
common
├── extension
│ ├── metadata_report_factory.go
config
├── metadata_report_config.go
metadata
├── metadata_info.go
├── configurableExporter.go // MetadataService 暴露接口定义，取消 extension 扩展
├── service.go // MetadataService 实现类
├── service_proxy.go // rpc 式调用 metadataService 接口，取消 extension 扩展
├── metadata_service.go // MetadataService 接口定义
├── mapping
│ ├── metadata
│ │ └── service_name_mapping.go
│ └── service_name_mapping.go
├── report
| ├── identifier
| │ ├── base_metadata_identifier.go
| │ ├── metadata_identifier.go
| │ ├── service_metadata_identifier.go
| │ ├── subscribe_metadata_identifier.go
│ ├── etcd
│ │ ├── report.go
│ ├── factory
│ │ └── report_factory.go
│ ├── nacos
│ │ └── report.go
| ├── zookeeper
| │ └── report.go
│ ├── delegate_report.go
│ ├── report.go
│ └── reporter_metric.go // metrics 相关，融入到基类或者 delegate_report
```
备注：
服务发现 zk 示例，路径 /services/{appName}/{IP}:{PORT}
```json
{
"name": "metrics-provider",
"id": "10.253.77.49:20880",
"address": "10.253.77.49",
"port": 20880,
"sslPort": null,
"payload": {
"@class": "org.apache.dubbo.registry.zookeeper.ZookeeperInstance",
"id": "10.253.77.49:20880",
"name": "metrics-provider",
"metadata": {
"dubbo.endpoints": "[{\"port\":20880,\"protocol\":\"dubbo\"}]",
"dubbo.metadata-service.url-params":
"{\"prefer.serialization\":\"fastjson2,hessian2\",\"version\":\"1.0.0\",\"dubbo\":\"2.0.2\",\"release\":\"3.2.1\",\"side\":\"provider\",\"port\":\"20881\",\"protocol\":\"dubbo\"}",
"dubbo.metadata.revision": "a12dcb4cf2519a7aa7cc2539a256648e",
"dubbo.metadata.storage-type": "local",
"timestamp": "1698398778406"
}
},
"registrationTimeUTC": 1698403384382,
"serviceType": "DYNAMIC",
"uriSpec": null
}
```
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