Service Discovery Extension

kitex-contrib has provided the DNS service discovery extensions.

If you want to adopt other service discovery protocol, such as ETCD, you can implement the Resolver interface, and clients can inject it by WithResolver Option.

Interface Definition

The interface is defined in pkg/discovery/discovery.go and is defined as follows:

type Resolver interface {
    Target(ctx context.Context, target rpcinfo.EndpointInfo) string
    Resolve(ctx context.Context, key string) (Result, error)
    Diff(key string, prev, next Result) (Change, bool)
    Name() string
}

type Result struct {
    Cacheable bool // if can be cached
    CacheKey  string // the unique key of cached result
    Instances []Instance // the result of service discovery
}

// the diff result
type Change struct {
    Result  Result
    Added   []Instance
    Updated []Instance
    Removed []Instance
}

Resolver interface detail:

  • Resolve: as the core method of Resolver, it obtains the service discovery result from target key
  • Target: it resolves the unique target endpoint that from the downstream endpoints provided by Resolve, and the result will be used as the unique key of the cache
  • Diff: it is used to compare the discovery results with the last time. The differences in results are used to notify other components, such as loadbalancer and circuitbreaker, etc
  • Name: it is used to specify a unique name for Resolver, and will use it to cache and reuse Resolver

Usage Example

You need to implement the the Resolver interface, and using it by Option:

import (
    "xx/kitex/client"
)

func main() {
    opt := client.WithResolver(YOUR_RESOLVER)

    // new client
    xxx.NewClient("destServiceName", opt)
}

Attention

To improve performance, Kitex reusing Resolver, so the Resolver method implementation must be concurrent security.