feat: added configuration center function (#3035)

Co-authored-by: aiden.ma <Aiden.ma@yijinin.com>

core/configcenter/subscriber/etcd.go

@@ -0,0 +1,60 @@
+package subscriber
+
+import (
+	"github.com/zeromicro/go-zero/core/discov"
+	"github.com/zeromicro/go-zero/core/logx"
+)
+
+type (
+	// etcdSubscriber is a subscriber that subscribes to etcd.
+	etcdSubscriber struct {
+		*discov.Subscriber
+	}
+
+	// EtcdConf is the configuration for etcd.
+	EtcdConf discov.EtcdConf
+)
+
+// MustNewEtcdSubscriber returns an etcd Subscriber, exits on errors.
+func MustNewEtcdSubscriber(conf EtcdConf) Subscriber {
+	s, err := NewEtcdSubscriber(conf)
+	logx.Must(err)
+
+	return s
+}
+
+// NewEtcdSubscriber returns an etcd Subscriber.
+func NewEtcdSubscriber(conf EtcdConf) (Subscriber, error) {
+	var opts = []discov.SubOption{
+		discov.WithDisablePrefix(),
+	}
+	if len(conf.User) != 0 {
+		opts = append(opts, discov.WithSubEtcdAccount(conf.User, conf.Pass))
+	}
+	if len(conf.CertFile) != 0 || len(conf.CertKeyFile) != 0 || len(conf.CACertFile) != 0 {
+		opts = append(opts,
+			discov.WithSubEtcdTLS(conf.CertFile, conf.CertKeyFile, conf.CACertFile, conf.InsecureSkipVerify))
+	}
+
+	s, err := discov.NewSubscriber(conf.Hosts, conf.Key, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	return &etcdSubscriber{Subscriber: s}, nil
+}
+
+// AddListener adds a listener to the subscriber.
+func (s *etcdSubscriber) AddListener(listener func()) error {
+	s.Subscriber.AddListener(listener)
+	return nil
+}
+
+// Value returns the value of the subscriber.
+func (s *etcdSubscriber) Value() (string, error) {
+	vs := s.Subscriber.Values()
+	if len(vs) != 0 {
+		return vs[len(vs)-1], nil
+	}
+	return "", nil
+}

core/configcenter/subscriber/subscriber.go

@@ -0,0 +1,9 @@
+package subscriber
+
+// Subscriber is the interface for configcenter subscribers.
+type Subscriber interface {
+	// AddListener adds a listener to the subscriber.
+	AddListener(listener func()) error
+	// Value returns the value of the subscriber.
+	Value() (string, error)
+}