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Commit transaction for each configuration change #17119

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Commit transaction for each configuration change #17119

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3 changes: 3 additions & 0 deletions server/etcdserver/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1809,6 +1809,9 @@ func (s *EtcdServer) apply(
var cc raftpb.ConfChange
pbutil.MustUnmarshal(&cc, e.Data)
removedSelf, err := s.applyConfChange(cc, confState, shouldApplyV3)
if err != nil {
s.lg.Error("failed to apply conf change", zap.Bool("shouldApplyV3", bool(shouldApplyV3)), zap.Error(err))
}
s.setAppliedIndex(e.Index)
s.setTerm(e.Term)
shouldStop = shouldStop || removedSelf
Expand Down
6 changes: 6 additions & 0 deletions server/etcdserver/server_test.go
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Expand Up @@ -298,6 +298,7 @@ func newServer(t *testing.T, recorder *nodeRecorder) *EtcdServer {
r: *newRaftNode(raftNodeConfig{lg: lg, Node: recorder}),
cluster: membership.NewCluster(lg),
consistIndex: cindex.NewConsistentIndex(be),
kv: mvcc.New(zap.NewNop(), be, &lease.FakeLessor{}, mvcc.StoreConfig{}),
}
srv.cluster.SetBackend(schema.NewMembershipBackend(lg, be))
srv.cluster.SetStore(v2store.New())
Expand Down Expand Up @@ -475,6 +476,7 @@ func TestApplyConfigChangeUpdatesConsistIndex(t *testing.T) {
w: wait.New(),
consistIndex: ci,
beHooks: serverstorage.NewBackendHooks(lg, ci),
kv: mvcc.New(zap.NewNop(), be, &lease.FakeLessor{}, mvcc.StoreConfig{}),
}

// create EntryConfChange entry
Expand Down Expand Up @@ -567,6 +569,7 @@ func TestApplyMultiConfChangeShouldStop(t *testing.T) {
w: wait.New(),
consistIndex: ci,
beHooks: serverstorage.NewBackendHooks(lg, ci),
kv: mvcc.New(zap.NewNop(), be, &lease.FakeLessor{}, mvcc.StoreConfig{}),
}
var ents []raftpb.Entry
for i := 1; i <= 4; i++ {
Expand Down Expand Up @@ -876,6 +879,7 @@ func TestAddMember(t *testing.T) {
SyncTicker: &time.Ticker{},
consistIndex: cindex.NewFakeConsistentIndex(0),
beHooks: serverstorage.NewBackendHooks(lg, nil),
kv: mvcc.New(zap.NewNop(), be, &lease.FakeLessor{}, mvcc.StoreConfig{}),
}
s.start()
m := membership.Member{ID: 1234, RaftAttributes: membership.RaftAttributes{PeerURLs: []string{"foo"}}}
Expand Down Expand Up @@ -981,6 +985,7 @@ func TestRemoveMember(t *testing.T) {
SyncTicker: &time.Ticker{},
consistIndex: cindex.NewFakeConsistentIndex(0),
beHooks: serverstorage.NewBackendHooks(lg, nil),
kv: mvcc.New(zap.NewNop(), be, &lease.FakeLessor{}, mvcc.StoreConfig{}),
}
s.start()
_, err := s.RemoveMember(context.Background(), 1234)
Expand Down Expand Up @@ -1030,6 +1035,7 @@ func TestUpdateMember(t *testing.T) {
SyncTicker: &time.Ticker{},
consistIndex: cindex.NewFakeConsistentIndex(0),
beHooks: serverstorage.NewBackendHooks(lg, nil),
kv: mvcc.New(zap.NewNop(), be, &lease.FakeLessor{}, mvcc.StoreConfig{}),
}
s.start()
wm := membership.Member{ID: 1234, RaftAttributes: membership.RaftAttributes{PeerURLs: []string{"http://127.0.0.1:1"}}}
Expand Down
21 changes: 20 additions & 1 deletion server/storage/schema/membership.go
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Expand Up @@ -72,9 +72,28 @@ func (s *membershipBackend) MustDeleteMemberFromBackend(id types.ID) {

tx := s.be.BatchTx()
tx.LockInsideApply()
defer tx.Unlock()
tx.UnsafeDelete(Members, mkey)
tx.UnsafePut(MembersRemoved, mkey, []byte("removed"))
tx.Unlock()

// We need to forcibly commit the transaction, otherwise etcd might
// run into a situation that it haven't finished committing the data
// into backend storage (note: etcd periodically commits the bbolt
// transactions instead of on each request) when it receives next
// confChange request. Accordingly, etcd may still reads the stale
// data from bbolt when processing next confChange request. So it
// breaks linearizability.
//
// Note we don't need to forcibly commit the transaction for other
// kinds of request (e.g. normal key/value operations, member add
// or update requests), because there is a buffer on top of the bbolt.
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// Each time when etcd reads data from backend storage, it will read
// data from both bbolt and the buffer. But there is no such a buffer
// for member delete requests.
//
// Please also refer to
// https://github.com/etcd-io/etcd/pull/17119#issuecomment-1857547158
s.be.ForceCommit()
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Should we be applying the same fix to MustSaveMemberToBackend?

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No, actually the comment right above s.be.ForceCommit() already explains the reason. Please feel free to ping me if you need further clarification.

Also note this PR only resolves the issue for conf change. We need to think about a more generic solution for all similar changes on bucket other than key, i.e auth, lease, etc.

}

func (s *membershipBackend) MustReadMembersFromBackend() (map[types.ID]*membership.Member, map[types.ID]bool) {
Expand Down
17 changes: 9 additions & 8 deletions tests/e2e/ctl_v3_member_no_proxy_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -40,28 +40,27 @@ func TestMemberReplace(t *testing.T) {
require.NoError(t, err)
defer epc.Close()

memberId := rand.Int() % len(epc.Procs)
member := epc.Procs[memberId]
memberIdx := rand.Int() % len(epc.Procs)
member := epc.Procs[memberIdx]
memberName := member.Config().Name
var endpoints []string
for i := 1; i < len(epc.Procs); i++ {
endpoints = append(endpoints, epc.Procs[(memberId+i)%len(epc.Procs)].EndpointsGRPC()...)
endpoints = append(endpoints, epc.Procs[(memberIdx+i)%len(epc.Procs)].EndpointsGRPC()...)
}
cc, err := e2e.NewEtcdctl(epc.Cfg.Client, endpoints)
require.NoError(t, err)

c := epc.Etcdctl()
memberID, found, err := getMemberIdByName(ctx, c, memberName)
memberID, found, err := getMemberIdByName(ctx, cc, memberName)
require.NoError(t, err)
require.Equal(t, found, true, "Member not found")

// Need to wait health interval for cluster to accept member changes
time.Sleep(etcdserver.HealthInterval)

t.Logf("Removing member %s", memberName)
_, err = c.MemberRemove(ctx, memberID)
_, err = cc.MemberRemove(ctx, memberID)
require.NoError(t, err)
_, found, err = getMemberIdByName(ctx, c, memberName)
_, found, err = getMemberIdByName(ctx, cc, memberName)
require.NoError(t, err)
require.Equal(t, found, false, "Expected member to be removed")
for member.IsRunning() {
Expand All @@ -82,12 +81,14 @@ func TestMemberReplace(t *testing.T) {
err = patchArgs(member.Config().Args, "initial-cluster-state", "existing")
require.NoError(t, err)

// Sleep 100ms to bypass the known issue https://github.com/etcd-io/etcd/issues/16687.
time.Sleep(100 * time.Millisecond)
t.Logf("Starting member %s", memberName)
err = member.Start(ctx)
require.NoError(t, err)
testutils.ExecuteUntil(ctx, t, func() {
for {
_, found, err := getMemberIdByName(ctx, c, memberName)
_, found, err := getMemberIdByName(ctx, cc, memberName)
if err != nil || !found {
time.Sleep(10 * time.Millisecond)
continue
Expand Down
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