From 125f3c3f9a014febf8df073e78a03c4cdb490aa0 Mon Sep 17 00:00:00 2001
From: Chris Ayoub <cayoub@hubspot.com>
Date: Tue, 29 Mar 2022 13:38:21 -0400
Subject: [PATCH] clientv3: filter learners members during autosync

This change is to ensure that all members returned during the client's
AutoSync are started and are not learners, which are not valid
etcd members to make requests to.
---
 client/v3/client.go      |  4 +++-
 client/v3/client_test.go | 46 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/client/v3/client.go b/client/v3/client.go
index 971fea607..747dc6d9c 100644
--- a/client/v3/client.go
+++ b/client/v3/client.go
@@ -186,7 +186,9 @@ func (c *Client) Sync(ctx context.Context) error {
 	}
 	var eps []string
 	for _, m := range mresp.Members {
-		eps = append(eps, m.ClientURLs...)
+		if len(m.Name) != 0 && !m.IsLearner {
+			eps = append(eps, m.ClientURLs...)
+		}
 	}
 	c.SetEndpoints(eps...)
 	return nil
diff --git a/client/v3/client_test.go b/client/v3/client_test.go
index b8c62a95b..da6f39de6 100644
--- a/client/v3/client_test.go
+++ b/client/v3/client_test.go
@@ -244,6 +244,24 @@ func TestAuthTokenBundleNoOverwrite(t *testing.T) {
 	}
 }
 
+func TestSyncFiltersMembers(t *testing.T) {
+	c, _ := NewClient(t, Config{Endpoints: []string{"http://254.0.0.1:12345"}})
+	defer c.Close()
+	c.Cluster = &mockCluster{
+		[]*etcdserverpb.Member{
+			{ID: 0, Name: "", ClientURLs: []string{"http://254.0.0.1:12345"}, IsLearner: false},
+			{ID: 1, Name: "isStarted", ClientURLs: []string{"http://254.0.0.2:12345"}, IsLearner: true},
+			{ID: 2, Name: "isStartedAndNotLearner", ClientURLs: []string{"http://254.0.0.3:12345"}, IsLearner: false},
+		},
+	}
+	c.Sync(context.Background())
+
+	endpoints := c.Endpoints()
+	if len(endpoints) != 1 || endpoints[0] != "http://254.0.0.3:12345" {
+		t.Error("Client.Sync uses learner and/or non-started member client URLs")
+	}
+}
+
 type mockAuthServer struct {
 	*etcdserverpb.UnimplementedAuthServer
 }
@@ -251,3 +269,31 @@ type mockAuthServer struct {
 func (mockAuthServer) Authenticate(context.Context, *etcdserverpb.AuthenticateRequest) (*etcdserverpb.AuthenticateResponse, error) {
 	return &etcdserverpb.AuthenticateResponse{Token: "mock-token"}, nil
 }
+
+type mockCluster struct {
+	members []*etcdserverpb.Member
+}
+
+func (mc *mockCluster) MemberList(ctx context.Context) (*MemberListResponse, error) {
+	return &MemberListResponse{Members: mc.members}, nil
+}
+
+func (mc *mockCluster) MemberAdd(ctx context.Context, peerAddrs []string) (*MemberAddResponse, error) {
+	return nil, nil
+}
+
+func (mc *mockCluster) MemberAddAsLearner(ctx context.Context, peerAddrs []string) (*MemberAddResponse, error) {
+	return nil, nil
+}
+
+func (mc *mockCluster) MemberRemove(ctx context.Context, id uint64) (*MemberRemoveResponse, error) {
+	return nil, nil
+}
+
+func (mc *mockCluster) MemberUpdate(ctx context.Context, id uint64, peerAddrs []string) (*MemberUpdateResponse, error) {
+	return nil, nil
+}
+
+func (mc *mockCluster) MemberPromote(ctx context.Context, id uint64) (*MemberPromoteResponse, error) {
+	return nil, nil
+}