xds

xDS support

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xDS is a set of discovery services that enables date-plane to discover various dynamic resources via querying from the management servers.

This project adds xDS support for Kitex and enables Kitex to perform in Proxyless mode. For more details of the design, please refer to the proposal.

Feature

• Service Discovery
• Traffic Route: supports exact prefix regex match for header and method
  • HTTP route configuration: configure via VirtualService.
    • Since Istio provides limited support for thrift protocol and most users are familiar with the config of VirtualService, we use a mapping from HTTP to Thrift in this configuration.
  • ThriftProxy: configure via patching EnvoyFilter.
    • The configuration in ThriftProxy is very limited.
• Timeout Configuration:
  • Configuration inside HTTP route configuration: configure via VirtualService.

Usage

There are two steps for enabling xDS for Kitex applications: 1. xDS module initialization and 2. Kitex Client/Server Option configuration.

xDS module

To enable xDS mode in Kitex, we should invoke xds.Init() to initialize the xds module, including the xdsResourceManager and xdsClient.

Bootstrap

The xdsClient is responsible for the interaction with the xDS Server (i.e. Istio). It needs some environment variables for initialization, which need to be set inside the spec.containers.env of the Kubernetes Manifest file in YAML format.

• POD_NAMESPACE: the namespace of the current service.
• POD_NAME: the name of this pod.
• INSTANCE_IP: the ip of this pod.

Add the following part to the definition of your container that uses xDS-enabled Kitex client.

- name: POD_NAMESPACE
valueFrom:
  fieldRef:
    fieldPath: metadata.namespace
- name: POD_NAME
valueFrom:
  fieldRef:
    fieldPath: metadata.name
- name: INSTANCE_IP
valueFrom:
  fieldRef:
    fieldPath: status.podIP

Client-side

For now, we only provide the support on the client-side. To use a xds-enabled Kitex client, you should specify destService using the URL of your target service and add one option WithXDSSuite.

• Construct a xds.ClientSuite that includes RouteMiddleware and Resolver, and then pass it into the WithXDSSuite option.

// import "github.com/cloudwego/kitex/pkg/xds"

client.WithXDSSuite(xds.ClientSuite{
	RouterMiddleware: xdssuite.NewXDSRouterMiddleware(),
	Resolver:         xdssuite.NewXDSResolver(),
}),

• The URL of the target service should be in the format, which follows the format in Kubernetes:

<service-name>.<namespace>.svc.cluster.local:<service-port>
<service-name>.<namespace>.svc:<service-port>
<service-name>.<namespace>:<service-port>
<service-name>:<service-port> // access the <service-name> in same namespace.

Traffic route based on Tag Match

We can define traffic route configuration via VirtualService in Istio.

The following example indicates that when the tag contains {"stage":"canary"} in the header, the request will be routed to the v1 subcluster of kitex-server.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: kitex-server
spec:
  hosts:
    - kitex-server
  http:
  - name: "route-based-on-tags"
    match:
      - headers:
          stage:
            exact: "canary"
      # support prefix match
      - headers:
          stage:
            prefix: "can"
      # support regex match
      - headers:
          stage:
            regex: "[canary|prod]"
    route:
    - destination:
        host: kitex-server
        subset: v1
      weight: 100
    timeout: 0.5s

The example of prefix and regex match like this:

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: kitex-server
spec:
  hosts:
    - kitex-server
  http:
  - name: "route-based-on-tags"
    match:
      # support prefix match
      - headers:
          stage:
            prefix: "can"
      # support regex match
      - headers:
          stage:
            regex: "[canary|prod]"
    route:
    - destination:
        host: kitex-server
        subset: v1
      weight: 100
    timeout: 0.5s

In order to match the rules defined in the VirtualService we need to specify the tags (metadata) of the traffic which will be used to match the rules.

For example: set the key and value to "stage" and "canary" to match the above rules defined in VirtualService.

• We can first define a MetaExtractor and pass it to RouterMiddleware through xdssuite.WithRouterMetaExtractor.
  • Notice: If RouterMetaExtractor is not configured, metainfo.GetAllValues will be used by default.

var (
	routeKey   = "stage"
	routeValue = "canary"
)

func routeByStage(ctx context.Context) map[string]string {
	if v, ok := metainfo.GetValue(ctx, routeKey); ok {
		return map[string]string{
			routeKey: v,
		}
	}
	return nil
}

// add the option
client.WithXDSSuite(xds2.ClientSuite{
	RouterMiddleware: xdssuite.NewXDSRouterMiddleware(
		// use this option to specify the meta extractor
		xdssuite.WithRouterMetaExtractor(routeByStage),
	),
	Resolver: xdssuite.NewXDSResolver(),
}),

• Set the metadata of the traffic (corresponding to the MetaExtractor) when make RPC Call. Here, we use metainfo.WithValue to specify the label of the traffic. Metadata will be extracted for route matching.

ctx := metainfo.WithValue(context.Background(), routeKey, routeValue)

Traffic route based on Method Match

Same as above, using VirtualService in Istio to define traffic routing configuration.

The example below shows that requests with method equal to SayHello are routed to the v1 subcluster of kitex-server. It should be noted that when defining rules, you need to include package name and service name, corresponding to namespace and service in thrift idl.

• uri: /${PackageName}.${ServiceName}/${MethodName}

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: kitex-server
spec:
  hosts:
    - kitex-server
  http:
  - name: "route-based-on-path"
    match:
      - uri:
          # /${PackageName}.${ServiceName}/${MethodName}
          exact: /proxyless.GreetService/SayHello
    route:
    - destination:
        host: kitex-server
        subset: v2
      weight: 100
    timeout: 0.5s

Example

The usage is as follows:

import (
	"github.com/cloudwego/kitex/client"
	xds2 "github.com/cloudwego/kitex/pkg/xds"
	"github.com/kitex-contrib/xds"
	"github.com/kitex-contrib/xds/xdssuite"
	"github.com/cloudwego/kitex-proxyless-test/service/codec/thrift/kitex_gen/proxyless/greetservice"
)

func main() {
	// initialize xds module
	err := xds.Init()
	if err != nil {
		return
	}
	
	// initialize the client
	cli, err := greetservice.NewClient(
		destService,
		client.WithXDSSuite(xds2.ClientSuite{
			RouterMiddleware: xdssuite.NewXDSRouterMiddleware(),
			Resolver:         xdssuite.NewXDSResolver(),
		}),
	)
	
	req := &proxyless.HelloRequest{Message: "Hello!"}
	resp, err := c.cli.SayHello1(
		ctx, 
		req, 
	) 
}

Detailed examples can be found here kitex-proxyless-example.

Limitation

mTLS

mTLS is not supported for now. Please disable mTLS via configuring PeerAuthentication.

apiVersion: "security.istio.io/v1beta1"
kind: "PeerAuthentication"
metadata:
  name: "default"
  namespace: {your_namespace}
spec:
  mtls:
    mode: DISABLE

Limited support for Service Governance

Current version only support Service Discovery, Traffic route and Timeout Configuration via xDS on the client-side.

Other features supported via xDS, including Load Balancing, Rate Limit and Retry etc, will be added in the future.

Compatibility

This package is only tested under Istio1.13.3.

maintained by: ppzqh

Dependencies

Kitex >= v0.4.0