dendrite/syncapi/storage/storage_test.go
Neil Alexander 02fe38e1f7
Per-user-per-device sync streams (#1068)
* Per-user-per-device sync streams

* Tweaks

* Tweaks

* Pass full device into CompleteSync

* Set user IDs and device IDs properly in tests

* Add new test, fix TestNewEventAndWasPreviouslyJoinedToRoom

* nolint a function that is not used yet

* Add test for waking up single device

* Hopefully unstick test

* Try to ensure that TestCorrectStreamWakeup doesn't block forever

* Update tests
2020-05-28 10:05:04 +01:00

570 lines
22 KiB
Go

package storage_test
import (
"context"
"crypto/ed25519"
"fmt"
"testing"
"time"
"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
"github.com/matrix-org/dendrite/syncapi/storage"
"github.com/matrix-org/dendrite/syncapi/storage/sqlite3"
"github.com/matrix-org/dendrite/syncapi/types"
"github.com/matrix-org/gomatrixserverlib"
)
var (
ctx = context.Background()
emptyStateKey = ""
testOrigin = gomatrixserverlib.ServerName("hollow.knight")
testRoomID = fmt.Sprintf("!hallownest:%s", testOrigin)
testUserIDA = fmt.Sprintf("@hornet:%s", testOrigin)
testUserIDB = fmt.Sprintf("@paleking:%s", testOrigin)
testUserDeviceA = authtypes.Device{
UserID: testUserIDA,
ID: "device_id_A",
DisplayName: "Device A",
}
testRoomVersion = gomatrixserverlib.RoomVersionV4
testKeyID = gomatrixserverlib.KeyID("ed25519:storage_test")
testPrivateKey = ed25519.NewKeyFromSeed([]byte{
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
})
)
func MustCreateEvent(t *testing.T, roomID string, prevs []gomatrixserverlib.HeaderedEvent, b *gomatrixserverlib.EventBuilder) gomatrixserverlib.HeaderedEvent {
b.RoomID = roomID
if prevs != nil {
prevIDs := make([]string, len(prevs))
for i := range prevs {
prevIDs[i] = prevs[i].EventID()
}
b.PrevEvents = prevIDs
}
e, err := b.Build(time.Now(), testOrigin, testKeyID, testPrivateKey, testRoomVersion)
if err != nil {
t.Fatalf("failed to build event: %s", err)
}
return e.Headered(testRoomVersion)
}
func MustCreateDatabase(t *testing.T) storage.Database {
db, err := sqlite3.NewDatabase("file::memory:")
if err != nil {
t.Fatalf("NewSyncServerDatasource returned %s", err)
}
return db
}
// Create a list of events which include a create event, join event and some messages.
func SimpleRoom(t *testing.T, roomID, userA, userB string) (msgs []gomatrixserverlib.HeaderedEvent, state []gomatrixserverlib.HeaderedEvent) {
var events []gomatrixserverlib.HeaderedEvent
events = append(events, MustCreateEvent(t, roomID, nil, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"room_version":"4","creator":"%s"}`, userA)),
Type: "m.room.create",
StateKey: &emptyStateKey,
Sender: userA,
Depth: int64(len(events) + 1),
}))
state = append(state, events[len(events)-1])
events = append(events, MustCreateEvent(t, roomID, []gomatrixserverlib.HeaderedEvent{events[len(events)-1]}, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"membership":"join"}`)),
Type: "m.room.member",
StateKey: &userA,
Sender: userA,
Depth: int64(len(events) + 1),
}))
state = append(state, events[len(events)-1])
for i := 0; i < 10; i++ {
events = append(events, MustCreateEvent(t, roomID, []gomatrixserverlib.HeaderedEvent{events[len(events)-1]}, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"body":"Message A %d"}`, i+1)),
Type: "m.room.message",
Sender: userA,
Depth: int64(len(events) + 1),
}))
}
events = append(events, MustCreateEvent(t, roomID, []gomatrixserverlib.HeaderedEvent{events[len(events)-1]}, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"membership":"join"}`)),
Type: "m.room.member",
StateKey: &userB,
Sender: userB,
Depth: int64(len(events) + 1),
}))
state = append(state, events[len(events)-1])
for i := 0; i < 10; i++ {
events = append(events, MustCreateEvent(t, roomID, []gomatrixserverlib.HeaderedEvent{events[len(events)-1]}, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"body":"Message B %d"}`, i+1)),
Type: "m.room.message",
Sender: userB,
Depth: int64(len(events) + 1),
}))
}
return events, state
}
func MustWriteEvents(t *testing.T, db storage.Database, events []gomatrixserverlib.HeaderedEvent) (positions []types.StreamPosition) {
for _, ev := range events {
var addStateEvents []gomatrixserverlib.HeaderedEvent
var addStateEventIDs []string
var removeStateEventIDs []string
if ev.StateKey() != nil {
addStateEvents = append(addStateEvents, ev)
addStateEventIDs = append(addStateEventIDs, ev.EventID())
}
pos, err := db.WriteEvent(ctx, &ev, addStateEvents, addStateEventIDs, removeStateEventIDs, nil, false)
if err != nil {
t.Fatalf("WriteEvent failed: %s", err)
}
fmt.Println("Event ID", ev.EventID(), " spos=", pos, "depth=", ev.Depth())
positions = append(positions, pos)
}
return
}
func TestWriteEvents(t *testing.T) {
t.Parallel()
db := MustCreateDatabase(t)
events, _ := SimpleRoom(t, testRoomID, testUserIDA, testUserIDB)
MustWriteEvents(t, db, events)
}
// These tests assert basic functionality of the IncrementalSync and CompleteSync functions.
func TestSyncResponse(t *testing.T) {
t.Parallel()
db := MustCreateDatabase(t)
events, state := SimpleRoom(t, testRoomID, testUserIDA, testUserIDB)
positions := MustWriteEvents(t, db, events)
latest, err := db.SyncPosition(ctx)
if err != nil {
t.Fatalf("failed to get SyncPosition: %s", err)
}
testCases := []struct {
Name string
DoSync func() (*types.Response, error)
WantTimeline []gomatrixserverlib.HeaderedEvent
WantState []gomatrixserverlib.HeaderedEvent
}{
// The purpose of this test is to make sure that incremental syncs are including up to the latest events.
// It's a basic sanity test that sync works. It creates a `since` token that is on the penultimate event.
// It makes sure the response includes the final event.
{
Name: "IncrementalSync penultimate",
DoSync: func() (*types.Response, error) {
from := types.NewStreamToken( // pretend we are at the penultimate event
positions[len(positions)-2], types.StreamPosition(0),
)
return db.IncrementalSync(ctx, testUserDeviceA, from, latest, 5, false)
},
WantTimeline: events[len(events)-1:],
},
// The purpose of this test is to check that passing a `numRecentEventsPerRoom` correctly limits the
// number of returned events. This is critical for big rooms hence the test here.
{
Name: "IncrementalSync limited",
DoSync: func() (*types.Response, error) {
from := types.NewStreamToken( // pretend we are 10 events behind
positions[len(positions)-11], types.StreamPosition(0),
)
// limit is set to 5
return db.IncrementalSync(ctx, testUserDeviceA, from, latest, 5, false)
},
// want the last 5 events, NOT the last 10.
WantTimeline: events[len(events)-5:],
},
// The purpose of this test is to check that CompleteSync returns all the current state as well as
// honouring the `numRecentEventsPerRoom` value
{
Name: "CompleteSync limited",
DoSync: func() (*types.Response, error) {
// limit set to 5
return db.CompleteSync(ctx, testUserDeviceA, 5)
},
// want the last 5 events
WantTimeline: events[len(events)-5:],
// want all state for the room
WantState: state,
},
// The purpose of this test is to check that CompleteSync can return everything with a high enough
// `numRecentEventsPerRoom`.
{
Name: "CompleteSync",
DoSync: func() (*types.Response, error) {
return db.CompleteSync(ctx, testUserDeviceA, len(events)+1)
},
WantTimeline: events,
// We want no state at all as that field in /sync is the delta between the token (beginning of time)
// and the START of the timeline.
},
}
for _, tc := range testCases {
t.Run(tc.Name, func(st *testing.T) {
res, err := tc.DoSync()
if err != nil {
st.Fatalf("failed to do sync: %s", err)
}
next := types.NewStreamToken(latest.PDUPosition(), latest.EDUPosition())
if res.NextBatch != next.String() {
st.Errorf("NextBatch got %s want %s", res.NextBatch, next.String())
}
roomRes, ok := res.Rooms.Join[testRoomID]
if !ok {
st.Fatalf("IncrementalSync response missing room %s - response: %+v", testRoomID, res)
}
assertEventsEqual(st, "state for "+testRoomID, false, roomRes.State.Events, tc.WantState)
assertEventsEqual(st, "timeline for "+testRoomID, false, roomRes.Timeline.Events, tc.WantTimeline)
})
}
}
func TestGetEventsInRangeWithPrevBatch(t *testing.T) {
t.Parallel()
db := MustCreateDatabase(t)
events, _ := SimpleRoom(t, testRoomID, testUserIDA, testUserIDB)
positions := MustWriteEvents(t, db, events)
latest, err := db.SyncPosition(ctx)
if err != nil {
t.Fatalf("failed to get SyncPosition: %s", err)
}
from := types.NewStreamToken(
positions[len(positions)-2], types.StreamPosition(0),
)
res, err := db.IncrementalSync(ctx, testUserDeviceA, from, latest, 5, false)
if err != nil {
t.Fatalf("failed to IncrementalSync with latest token")
}
roomRes, ok := res.Rooms.Join[testRoomID]
if !ok {
t.Fatalf("IncrementalSync response missing room %s - response: %+v", testRoomID, res)
}
// returns the last event "Message 10"
assertEventsEqual(t, "IncrementalSync Timeline", false, roomRes.Timeline.Events, reversed(events[len(events)-1:]))
prev := roomRes.Timeline.PrevBatch
if prev == "" {
t.Fatalf("IncrementalSync expected prev_batch token")
}
prevBatchToken, err := types.NewTopologyTokenFromString(prev)
if err != nil {
t.Fatalf("failed to NewTopologyTokenFromString : %s", err)
}
// backpaginate 5 messages starting at the latest position.
// head towards the beginning of time
to := types.NewTopologyToken(0, 0)
paginatedEvents, err := db.GetEventsInTopologicalRange(ctx, &prevBatchToken, &to, testRoomID, 5, true)
if err != nil {
t.Fatalf("GetEventsInRange returned an error: %s", err)
}
gots := gomatrixserverlib.HeaderedToClientEvents(db.StreamEventsToEvents(&testUserDeviceA, paginatedEvents), gomatrixserverlib.FormatAll)
assertEventsEqual(t, "", true, gots, reversed(events[len(events)-6:len(events)-1]))
}
// The purpose of this test is to ensure that backfill does indeed go backwards, using a stream token.
func TestGetEventsInRangeWithStreamToken(t *testing.T) {
t.Parallel()
db := MustCreateDatabase(t)
events, _ := SimpleRoom(t, testRoomID, testUserIDA, testUserIDB)
MustWriteEvents(t, db, events)
latest, err := db.SyncPosition(ctx)
if err != nil {
t.Fatalf("failed to get SyncPosition: %s", err)
}
// head towards the beginning of time
to := types.NewStreamToken(0, 0)
// backpaginate 5 messages starting at the latest position.
paginatedEvents, err := db.GetEventsInStreamingRange(ctx, &latest, &to, testRoomID, 5, true)
if err != nil {
t.Fatalf("GetEventsInRange returned an error: %s", err)
}
gots := gomatrixserverlib.HeaderedToClientEvents(db.StreamEventsToEvents(&testUserDeviceA, paginatedEvents), gomatrixserverlib.FormatAll)
assertEventsEqual(t, "", true, gots, reversed(events[len(events)-5:]))
}
// The purpose of this test is to ensure that backfill does indeed go backwards, using a topology token
func TestGetEventsInRangeWithTopologyToken(t *testing.T) {
t.Parallel()
db := MustCreateDatabase(t)
events, _ := SimpleRoom(t, testRoomID, testUserIDA, testUserIDB)
MustWriteEvents(t, db, events)
from, err := db.MaxTopologicalPosition(ctx, testRoomID)
if err != nil {
t.Fatalf("failed to get MaxTopologicalPosition: %s", err)
}
// head towards the beginning of time
to := types.NewTopologyToken(0, 0)
// backpaginate 5 messages starting at the latest position.
paginatedEvents, err := db.GetEventsInTopologicalRange(ctx, &from, &to, testRoomID, 5, true)
if err != nil {
t.Fatalf("GetEventsInRange returned an error: %s", err)
}
gots := gomatrixserverlib.HeaderedToClientEvents(db.StreamEventsToEvents(&testUserDeviceA, paginatedEvents), gomatrixserverlib.FormatAll)
assertEventsEqual(t, "", true, gots, reversed(events[len(events)-5:]))
}
// The purpose of this test is to make sure that backpagination returns all events, even if some events have the same depth.
// For cases where events have the same depth, the streaming token should be used to tie break so events written via WriteEvent
// will appear FIRST when going backwards. This test creates a DAG like:
// .-----> Message ---.
// Create -> Membership --------> Message -------> Message
// `-----> Message ---`
// depth 1 2 3 4
//
// With a total depth of 4. It tests that:
// - Backpagination over the whole fork should include all messages and not leave any out.
// - Backpagination from the middle of the fork should not return duplicates (things later than the token).
func TestGetEventsInRangeWithEventsSameDepth(t *testing.T) {
t.Parallel()
db := MustCreateDatabase(t)
var events []gomatrixserverlib.HeaderedEvent
events = append(events, MustCreateEvent(t, testRoomID, nil, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"room_version":"4","creator":"%s"}`, testUserIDA)),
Type: "m.room.create",
StateKey: &emptyStateKey,
Sender: testUserIDA,
Depth: int64(len(events) + 1),
}))
events = append(events, MustCreateEvent(t, testRoomID, []gomatrixserverlib.HeaderedEvent{events[len(events)-1]}, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"membership":"join"}`)),
Type: "m.room.member",
StateKey: &testUserIDA,
Sender: testUserIDA,
Depth: int64(len(events) + 1),
}))
// fork the dag into three, same prev_events and depth
parent := []gomatrixserverlib.HeaderedEvent{events[len(events)-1]}
depth := int64(len(events) + 1)
for i := 0; i < 3; i++ {
events = append(events, MustCreateEvent(t, testRoomID, parent, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"body":"Message A %d"}`, i+1)),
Type: "m.room.message",
Sender: testUserIDA,
Depth: depth,
}))
}
// merge the fork, prev_events are all 3 messages, depth is increased by 1.
events = append(events, MustCreateEvent(t, testRoomID, events[len(events)-3:], &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"body":"Message merge"}`)),
Type: "m.room.message",
Sender: testUserIDA,
Depth: depth + 1,
}))
MustWriteEvents(t, db, events)
fromLatest, err := db.EventPositionInTopology(ctx, events[len(events)-1].EventID())
if err != nil {
t.Fatalf("failed to get EventPositionInTopology: %s", err)
}
fromFork, err := db.EventPositionInTopology(ctx, events[len(events)-3].EventID()) // Message 2
if err != nil {
t.Fatalf("failed to get EventPositionInTopology for event: %s", err)
}
// head towards the beginning of time
to := types.NewTopologyToken(0, 0)
testCases := []struct {
Name string
From types.TopologyToken
Limit int
Wants []gomatrixserverlib.HeaderedEvent
}{
{
Name: "Pagination over the whole fork",
From: fromLatest,
Limit: 5,
Wants: reversed(events[len(events)-5:]),
},
{
Name: "Paginating to the middle of the fork",
From: fromLatest,
Limit: 2,
Wants: reversed(events[len(events)-2:]),
},
{
Name: "Pagination FROM the middle of the fork",
From: fromFork,
Limit: 3,
Wants: reversed(events[len(events)-5 : len(events)-2]),
},
}
for _, tc := range testCases {
// backpaginate messages starting at the latest position.
paginatedEvents, err := db.GetEventsInTopologicalRange(ctx, &tc.From, &to, testRoomID, tc.Limit, true)
if err != nil {
t.Fatalf("%s GetEventsInRange returned an error: %s", tc.Name, err)
}
gots := gomatrixserverlib.HeaderedToClientEvents(db.StreamEventsToEvents(&testUserDeviceA, paginatedEvents), gomatrixserverlib.FormatAll)
assertEventsEqual(t, tc.Name, true, gots, tc.Wants)
}
}
// The purpose of this test is to make sure that the query to pull out events is honouring the room ID correctly.
// It works by creating two rooms with the same events in them, then selecting events by topological range.
// Specifically, we know that events with the same depth but lower stream positions are selected, and it's possible
// that this check isn't using the room ID if the brackets are wrong in the SQL query.
func TestGetEventsInTopologicalRangeMultiRoom(t *testing.T) {
t.Parallel()
db := MustCreateDatabase(t)
makeEvents := func(roomID string) (events []gomatrixserverlib.HeaderedEvent) {
events = append(events, MustCreateEvent(t, roomID, nil, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"room_version":"4","creator":"%s"}`, testUserIDA)),
Type: "m.room.create",
StateKey: &emptyStateKey,
Sender: testUserIDA,
Depth: int64(len(events) + 1),
}))
events = append(events, MustCreateEvent(t, roomID, []gomatrixserverlib.HeaderedEvent{events[len(events)-1]}, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"membership":"join"}`)),
Type: "m.room.member",
StateKey: &testUserIDA,
Sender: testUserIDA,
Depth: int64(len(events) + 1),
}))
return
}
roomA := "!room_a:" + string(testOrigin)
roomB := "!room_b:" + string(testOrigin)
eventsA := makeEvents(roomA)
eventsB := makeEvents(roomB)
MustWriteEvents(t, db, eventsA)
MustWriteEvents(t, db, eventsB)
from, err := db.MaxTopologicalPosition(ctx, roomB)
if err != nil {
t.Fatalf("failed to get MaxTopologicalPosition: %s", err)
}
// head towards the beginning of time
to := types.NewTopologyToken(0, 0)
// Query using room B as room A was inserted first and hence A will have lower stream positions but identical depths,
// allowing this bug to surface.
paginatedEvents, err := db.GetEventsInTopologicalRange(ctx, &from, &to, roomB, 5, true)
if err != nil {
t.Fatalf("GetEventsInRange returned an error: %s", err)
}
gots := gomatrixserverlib.HeaderedToClientEvents(db.StreamEventsToEvents(&testUserDeviceA, paginatedEvents), gomatrixserverlib.FormatAll)
assertEventsEqual(t, "", true, gots, reversed(eventsB))
}
// The purpose of this test is to make sure that events are returned in the right *order* when they have been inserted in a manner similar to
// how any kind of backfill operation will insert the events. This test inserts the SimpleRoom events in a manner similar to how backfill over
// federation would:
// - First inserts join event of test user C
// - Inserts chunks of history in strata e.g (25-30, 20-25, 15-20, 10-15, 5-10, 0-5).
// The test then does a backfill to ensure that the response is ordered correctly according to depth.
func TestGetEventsInRangeWithEventsInsertedLikeBackfill(t *testing.T) {
t.Parallel()
db := MustCreateDatabase(t)
events, _ := SimpleRoom(t, testRoomID, testUserIDA, testUserIDB)
// "federation" join
userC := fmt.Sprintf("@radiance:%s", testOrigin)
joinEvent := MustCreateEvent(t, testRoomID, []gomatrixserverlib.HeaderedEvent{events[len(events)-1]}, &gomatrixserverlib.EventBuilder{
Content: []byte(fmt.Sprintf(`{"membership":"join"}`)),
Type: "m.room.member",
StateKey: &userC,
Sender: userC,
Depth: int64(len(events) + 1),
})
MustWriteEvents(t, db, []gomatrixserverlib.HeaderedEvent{joinEvent})
// Sync will return this for the prev_batch
from := topologyTokenBefore(t, db, joinEvent.EventID())
// inject events in batches as if they were from backfill
// e.g [1,2,3,4,5,6] => [4,5,6] , [1,2,3]
chunkSize := 5
for i := len(events); i >= 0; i -= chunkSize {
start := i - chunkSize
if start < 0 {
start = 0
}
backfill := events[start:i]
MustWriteEvents(t, db, backfill)
}
// head towards the beginning of time
to := types.NewTopologyToken(0, 0)
// starting at `from`, backpaginate to the beginning of time, asserting as we go.
chunkSize = 3
events = reversed(events)
for i := 0; i < len(events); i += chunkSize {
paginatedEvents, err := db.GetEventsInTopologicalRange(ctx, from, &to, testRoomID, chunkSize, true)
if err != nil {
t.Fatalf("GetEventsInRange returned an error: %s", err)
}
gots := gomatrixserverlib.HeaderedToClientEvents(db.StreamEventsToEvents(&testUserDeviceA, paginatedEvents), gomatrixserverlib.FormatAll)
endi := i + chunkSize
if endi > len(events) {
endi = len(events)
}
assertEventsEqual(t, from.String(), true, gots, events[i:endi])
from = topologyTokenBefore(t, db, paginatedEvents[len(paginatedEvents)-1].EventID())
}
}
func assertEventsEqual(t *testing.T, msg string, checkRoomID bool, gots []gomatrixserverlib.ClientEvent, wants []gomatrixserverlib.HeaderedEvent) {
if len(gots) != len(wants) {
t.Fatalf("%s response returned %d events, want %d", msg, len(gots), len(wants))
}
for i := range gots {
g := gots[i]
w := wants[i]
if g.EventID != w.EventID() {
t.Errorf("%s event[%d] event_id mismatch: got %s want %s", msg, i, g.EventID, w.EventID())
}
if g.Sender != w.Sender() {
t.Errorf("%s event[%d] sender mismatch: got %s want %s", msg, i, g.Sender, w.Sender())
}
if checkRoomID && g.RoomID != w.RoomID() {
t.Errorf("%s event[%d] room_id mismatch: got %s want %s", msg, i, g.RoomID, w.RoomID())
}
if g.Type != w.Type() {
t.Errorf("%s event[%d] event type mismatch: got %s want %s", msg, i, g.Type, w.Type())
}
if g.OriginServerTS != w.OriginServerTS() {
t.Errorf("%s event[%d] origin_server_ts mismatch: got %v want %v", msg, i, g.OriginServerTS, w.OriginServerTS())
}
if string(g.Content) != string(w.Content()) {
t.Errorf("%s event[%d] content mismatch: got %s want %s", msg, i, string(g.Content), string(w.Content()))
}
if string(g.Unsigned) != string(w.Unsigned()) {
t.Errorf("%s event[%d] unsigned mismatch: got %s want %s", msg, i, string(g.Unsigned), string(w.Unsigned()))
}
if (g.StateKey == nil && w.StateKey() != nil) || (g.StateKey != nil && w.StateKey() == nil) {
t.Errorf("%s event[%d] state_key [not] missing: got %v want %v", msg, i, g.StateKey, w.StateKey())
continue
}
if g.StateKey != nil {
if !w.StateKeyEquals(*g.StateKey) {
t.Errorf("%s event[%d] state_key mismatch: got %s want %s", msg, i, *g.StateKey, *w.StateKey())
}
}
}
}
func topologyTokenBefore(t *testing.T, db storage.Database, eventID string) *types.TopologyToken {
tok, err := db.EventPositionInTopology(ctx, eventID)
if err != nil {
t.Fatalf("failed to get EventPositionInTopology: %s", err)
}
tok.Decrement()
return &tok
}
func reversed(in []gomatrixserverlib.HeaderedEvent) []gomatrixserverlib.HeaderedEvent {
out := make([]gomatrixserverlib.HeaderedEvent, len(in))
for i := 0; i < len(in); i++ {
out[i] = in[len(in)-i-1]
}
return out
}