Switch to error on self-join attempt

store/store.go

@@ -33,6 +33,10 @@ var (
 	// operation.
 	ErrNotLeader = errors.New("not leader")
 
+	// ErrSelfJoin is returned when a join-request is received from a node
+	// with the same Raft ID as this node.
+	ErrSelfJoin = errors.New("self-join attempted")
+
 	// ErrStaleRead is returned if the executing the query would violate the
 	// requested freshness.
 	ErrStaleRead = errors.New("stale read")
@@ -891,8 +895,7 @@ func (s *Store) Join(id, addr string, voter bool) error {
 		return ErrNotLeader
 	}
 	if id == s.raftID {
-		s.logger.Printf("ignoring join-request with same ID as this node")
+		return ErrSelfJoin
-		return nil
 	}
 
 	configFuture := s.raft.GetConfiguration()

store/store_test.go

@@ -2,6 +2,7 @@ package store
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"math/rand"
@@ -993,6 +994,32 @@ func Test_SingleNodeRecoverNetworkChangeSnapshot(t *testing.T) {
 	}
 }
 
+func Test_SingleNodeSelfJoinFail(t *testing.T) {
+	s0, ln0 := mustNewStore(true)
+	defer os.RemoveAll(s0.Path())
+	defer ln0.Close()
+	if err := s0.Open(); err != nil {
+		t.Fatalf("failed to open single-node store: %s", err.Error())
+	}
+	defer s0.Close(true)
+
+	if err := s0.Bootstrap(NewServer(s0.ID(), s0.Addr(), true)); err != nil {
+		t.Fatalf("failed to bootstrap single-node store: %s", err.Error())
+	}
+	if _, err := s0.WaitForLeader(10 * time.Second); err != nil {
+		t.Fatalf("Error waiting for leader: %s", err)
+	}
+
+	// Self-join should fail.
+	err := s0.Join(s0.ID(), s0.Addr(), true)
+	if err == nil {
+		t.Fatalf("failed to receive error for self-join")
+	}
+	if !errors.Is(err, ErrSelfJoin) {
+		t.Fatalf("received wrong error for self-join attempt: %s", err)
+	}
+}
+
 func Test_MultiNodeJoinRemove(t *testing.T) {
 	s0, ln0 := mustNewStore(true)
 	defer os.RemoveAll(s0.Path())