resolver.go

// Copyright 2017 The go-vgo Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// https://github.com/go-vgo/gt/blob/master/LICENSE
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

package grpclb

import (
	"errors"
	"fmt"
	"strings"

	etcd3 "go.etcd.io/etcd/clientv3"
	"google.golang.org/grpc/naming"
)

// resolver is the implementation of grpc.naming.Resolver
type resolver struct {
	serviceName string // service name to resolve
}

// NewResolver return resolver with service name
func NewResolver(serviceName string) *resolver {
	return &resolver{serviceName: serviceName}
}

// Resolve to resolve the service from etcd, target is the dial address of etcd
// target example: "http://127.0.0.1:2379,http://127.0.0.1:12379,http://127.0.0.1:22379"
func (re *resolver) Resolve(target string) (naming.Watcher, error) {
	if re.serviceName == "" {
		return nil, errors.New("grpclb: no service name provided")
	}

	// generate etcd client
	client, err := etcd3.New(etcd3.Config{
		Endpoints: strings.Split(target, ","),
	})
	if err != nil {
		return nil, fmt.Errorf("grpclb: creat etcd3 client failed: %s", err.Error())
	}

	// Return watcher
	return newWatcher(re, *client), nil
	// return &watcher{re: re, client: *client}, nil
}