micro/sync/leader/etcd/etcd.go

package etcd

import (
	"context"
	"log"
	"path"
	"strings"

	"github.com/micro/go-micro/sync/leader"
	client "go.etcd.io/etcd/clientv3"
	cc "go.etcd.io/etcd/clientv3/concurrency"
)

type etcdLeader struct {
	opts   leader.Options
	path   string
	client *client.Client
}

type etcdElected struct {
	s  *cc.Session
	e  *cc.Election
	id string
}

func (e *etcdLeader) Elect(id string, opts ...leader.ElectOption) (leader.Elected, error) {
	var options leader.ElectOptions
	for _, o := range opts {
		o(&options)
	}

	// make path
	path := path.Join(e.path, strings.Replace(id, "/", "-", -1))

	s, err := cc.NewSession(e.client)
	if err != nil {
		return nil, err
	}

	l := cc.NewElection(s, path)

	ctx, _ := context.WithCancel(context.Background())

	if err := l.Campaign(ctx, id); err != nil {
		return nil, err
	}

	return &etcdElected{
		e:  l,
		id: id,
	}, nil
}

func (e *etcdLeader) Follow() chan string {
	ch := make(chan string)

	s, err := cc.NewSession(e.client)
	if err != nil {
		return ch
	}

	l := cc.NewElection(s, e.path)
	ech := l.Observe(context.Background())

	go func() {
		for {
			select {
			case r, ok := <-ech:
				if !ok {
					return
				}
				ch <- string(r.Kvs[0].Value)
			}
		}
	}()

	return ch
}

func (e *etcdLeader) String() string {
	return "etcd"
}

func (e *etcdElected) Reelect() error {
	ctx, _ := context.WithCancel(context.Background())
	return e.e.Campaign(ctx, e.id)
}

func (e *etcdElected) Revoked() chan bool {
	ch := make(chan bool, 1)
	ech := e.e.Observe(context.Background())

	go func() {
		for r := range ech {
			if string(r.Kvs[0].Value) != e.id {
				ch <- true
				close(ch)
				return
			}
		}
	}()

	return ch
}

func (e *etcdElected) Resign() error {
	return e.e.Resign(context.Background())
}

func (e *etcdElected) Id() string {
	return e.id
}

func NewLeader(opts ...leader.Option) leader.Leader {
	var options leader.Options
	for _, o := range opts {
		o(&options)
	}

	var endpoints []string

	for _, addr := range options.Nodes {
		if len(addr) > 0 {
			endpoints = append(endpoints, addr)
		}
	}

	if len(endpoints) == 0 {
		endpoints = []string{"http://127.0.0.1:2379"}
	}

	// TODO: parse addresses
	c, err := client.New(client.Config{
		Endpoints: endpoints,
	})
	if err != nil {
		log.Fatal(err)
	}

	return &etcdLeader{
		path:   "/micro/leader",
		client: c,
		opts:   options,
	}
}