xds

最早由 Envoy 开发，用于构建 ServiceMesh 统一的 DP 接口。

xDS API - 一套 DP API - Mesh CP <-> Proxies
- 用于 gRPC Mesh - xds://pkg.service
- gRPC 集成了 xDS grpc.Dial("xds:///my-service")
  - 走控制面去发现服务
负载均衡
- LDS - Listener Discovery Service - type.googleapis.com/envoy.config.listener.v3.Listener
  - 监听器发现服务
- RDS - Route Discovery Service - type.googleapis.com/envoy.config.route.v3.RouteConfiguration
  - 路由发现服务
- CDS - Cluster Discovery Service - type.googleapis.com/envoy.config.cluster.v3.Cluster
  - 集群发现服务
- EDS - Endpoint Discovery Service - type.googleapis.com/envoy.config.endpoint.v3.ClusterLoadAssignment
  - 端点发现服务
- ADS - Aggregate Discovery Service - gRPC
  - 聚合发现服务
  - 聚合所有 LDS, RDS, CDS, EDS 到一个服务
  - https://github.com/envoyproxy/envoy/blob/main/api/envoy/service/discovery/v3/ads.proto
负载报告 - LRS
xDSv3
gRPC Proxyless
Proxyless Service Mesh
控制面
- Istio
- Kuma
- AWS App Mesh
- Aliyun ASM
- GCP Traffic Director
- envoyproxy/go-control-plane
数据面
- Envoy, MOSN, AeroFS
UDPA - Universal Data Plane API
- 服务发现，负载均衡分配，路由发现，监听器配置，安全发现，负载报告，运行状况检查委托
参考
- adopted by
  - Apache Dubbo 3.0 集成
  - 字节 Kitex Go RPC 框架
  - 百度 bRPC
- envoyproxy/data-plane-api
- xDS REST and gRPC protocol

Role	For
gRPC	高性能通信
Kubernetes	服务注册、服务发现、健康检测
Istio	路由、负载，服务治理：熔断、重拾，安全：认证、mTLS，可观察性：trace、log、metrics

gRPC xDS

GRPC_XDS_BOOTSTRAP
参考
- grpc-ecosystem/grpcdebug
  - 可用于 debug xds
- salrashid123/grpc_xds
- xDS Features in gRPC
- go grpc xds example
- gRPC A27: xDS-Based Global Load Balancing

{
  // The xDS server to talk to.  The value is an array to allow for a
  // future change to add support for failing over to a secondary xDS server
  // if the primary is down, but for now, only the first entry in the
  // array will be used.
  "xds_servers": [
    {
      "server_uri": "", //<string containing URI of xds server>,
      // List of channel creds; client will stop at the first type it
      // supports.  This field is required and must contain at least one
      // channel creds type that the client supports.
      "channel_creds": [
        {
          "type": "", // google_default, insecure
          // The "config" field is optional; it may be missing if the
          // credential type does not require config parameters.
          "config": "" //<JSON object containing config for the type>
        }
      ],
      "server_features": ["xds_v3"]
    }
  ],
  // JSON of proto
  // https://github.com/envoyproxy/data-plane-api/blob/1adb5d54abb0e28ca409254d26fad1cf5535239b/envoy/api/v2/core/base.proto#L85-L118
  "node": {
    "id": "",
    "cluster": "",
    "metadata": {},
    "locality": {
      "region": "",
      // https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-regions-availability-zones.html
      // https://cloud.google.com/compute/docs/regions-zones/
      "zone": "",
      "sub_zone": ""
    },
    "build_version": ""
  }
}

gRPC xDS​

gRPC xDS