fix endless loop caused by ErrCompacted (#3774)

Co-authored-by: lidengfu <lidengfu@excean.com>

core/discov/internal/registry.go

@@ -2,6 +2,7 @@ package internal
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"sort"
@@ -14,6 +15,7 @@ import (
 	"github.com/zeromicro/go-zero/core/logx"
 	"github.com/zeromicro/go-zero/core/syncx"
 	"github.com/zeromicro/go-zero/core/threading"
+	v3rpc "go.etcd.io/etcd/api/v3/v3rpc/rpctypes"
 	clientv3 "go.etcd.io/etcd/client/v3"
 )
 
@@ -288,13 +290,18 @@ func (c *cluster) reload(cli EtcdClient) {
 
 func (c *cluster) watch(cli EtcdClient, key string, rev int64) {
 	for {
-		if c.watchStream(cli, key, rev) {
+		err := c.watchStream(cli, key, rev)
+		if err == nil {
 			return
 		}
+		if rev != 0 && errors.Is(err, v3rpc.ErrCompacted) {
+			logx.Errorf("etcd watch stream has been compacted, try to reload, rev %v", rev)
+			rev = c.load(cli, key)
+		}
 	}
 }
 
-func (c *cluster) watchStream(cli EtcdClient, key string, rev int64) bool {
+func (c *cluster) watchStream(cli EtcdClient, key string, rev int64) error {
 	var rch clientv3.WatchChan
 	if rev != 0 {
 		rch = cli.Watch(clientv3.WithRequireLeader(c.context(cli)), makeKeyPrefix(key), clientv3.WithPrefix(),
@@ -308,20 +315,20 @@ func (c *cluster) watchStream(cli EtcdClient, key string, rev int64) bool {
 		case wresp, ok := <-rch:
 			if !ok {
 				logx.Error("etcd monitor chan has been closed")
-				return false
+				return errors.New("etcd monitor chan has been closed")
 			}
 			if wresp.Canceled {
 				logx.Errorf("etcd monitor chan has been canceled, error: %v", wresp.Err())
-				return false
+				return wresp.Err()
 			}
 			if wresp.Err() != nil {
 				logx.Error(fmt.Sprintf("etcd monitor chan error: %v", wresp.Err()))
-				return false
+				return wresp.Err()
 			}
 
 			c.handleWatchEvents(key, wresp.Events)
 		case <-c.done:
-			return true
+			return nil
 		}
 	}
 }