dendrite/syncapi/sync/notifier.go

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// Copyright 2017 Vector Creations Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package sync
import (
"context"
"sync"
"time"
"github.com/matrix-org/dendrite/syncapi/storage"
"github.com/matrix-org/dendrite/syncapi/types"
"github.com/matrix-org/gomatrixserverlib"
log "github.com/sirupsen/logrus"
)
// Notifier will wake up sleeping requests when there is some new data.
// It does not tell requests what that data is, only the sync position which
// they can use to get at it. This is done to prevent races whereby we tell the caller
// the event, but the token has already advanced by the time they fetch it, resulting
// in missed events.
type Notifier struct {
// A map of RoomID => Set<UserID> : Must only be accessed by the OnNewEvent goroutine
roomIDToJoinedUsers map[string]userIDSet
// Protects currPos and userStreams.
streamLock *sync.Mutex
// The latest sync position
currPos types.SyncPosition
// A map of user_id => UserStream which can be used to wake a given user's /sync request.
userStreams map[string]*UserStream
// The last time we cleaned out stale entries from the userStreams map
lastCleanUpTime time.Time
}
// NewNotifier creates a new notifier set to the given sync position.
// In order for this to be of any use, the Notifier needs to be told all rooms and
// the joined users within each of them by calling Notifier.Load(*storage.SyncServerDatabase).
func NewNotifier(pos types.SyncPosition) *Notifier {
return &Notifier{
currPos: pos,
roomIDToJoinedUsers: make(map[string]userIDSet),
userStreams: make(map[string]*UserStream),
streamLock: &sync.Mutex{},
lastCleanUpTime: time.Now(),
}
}
// OnNewEvent is called when a new event is received from the room server. Must only be
// called from a single goroutine, to avoid races between updates which could set the
// current sync position incorrectly.
// Chooses which user sync streams to update by a provided *gomatrixserverlib.Event
// (based on the users in the event's room),
// a roomID directly, or a list of user IDs, prioritised by parameter ordering.
// posUpdate contains the latest position(s) for one or more types of events.
// If a position in posUpdate is 0, it means no updates are available of that type.
// Typically a consumer supplies a posUpdate with the latest sync position for the
// event type it handles, leaving other fields as 0.
func (n *Notifier) OnNewEvent(
ev *gomatrixserverlib.Event, roomID string, userIDs []string,
posUpdate types.SyncPosition,
) {
// update the current position then notify relevant /sync streams.
// This needs to be done PRIOR to waking up users as they will read this value.
n.streamLock.Lock()
defer n.streamLock.Unlock()
latestPos := n.currPos.WithUpdates(posUpdate)
n.currPos = latestPos
n.removeEmptyUserStreams()
if ev != nil {
// Map this event's room_id to a list of joined users, and wake them up.
usersToNotify := n.joinedUsers(ev.RoomID())
// If this is an invite, also add in the invitee to this list.
if ev.Type() == "m.room.member" && ev.StateKey() != nil {
targetUserID := *ev.StateKey()
membership, err := ev.Membership()
if err != nil {
log.WithError(err).WithField("event_id", ev.EventID()).Errorf(
"Notifier.OnNewEvent: Failed to unmarshal member event",
)
} else {
// Keep the joined user map up-to-date
switch membership {
case "invite":
usersToNotify = append(usersToNotify, targetUserID)
case "join":
// Manually append the new user's ID so they get notified
// along all members in the room
usersToNotify = append(usersToNotify, targetUserID)
n.addJoinedUser(ev.RoomID(), targetUserID)
case "leave":
fallthrough
case "ban":
n.removeJoinedUser(ev.RoomID(), targetUserID)
}
}
}
n.wakeupUsers(usersToNotify, latestPos)
} else if roomID != "" {
n.wakeupUsers(n.joinedUsers(roomID), latestPos)
} else if len(userIDs) > 0 {
n.wakeupUsers(userIDs, latestPos)
} else {
log.WithFields(log.Fields{
"posUpdate": posUpdate.String,
}).Warn("Notifier.OnNewEvent called but caller supplied no user to wake up")
}
}
// GetListener returns a UserStreamListener that can be used to wait for
// updates for a user. Must be closed.
// notify for anything before sincePos
func (n *Notifier) GetListener(req syncRequest) UserStreamListener {
// Do what synapse does: https://github.com/matrix-org/synapse/blob/v0.20.0/synapse/notifier.py#L298
// - Bucket request into a lookup map keyed off a list of joined room IDs and separately a user ID
// - Incoming events wake requests for a matching room ID
// - Incoming events wake requests for a matching user ID (needed for invites)
// TODO: v1 /events 'peeking' has an 'explicit room ID' which is also tracked,
// but given we don't do /events, let's pretend it doesn't exist.
n.streamLock.Lock()
defer n.streamLock.Unlock()
n.removeEmptyUserStreams()
return n.fetchUserStream(req.device.UserID, true).GetListener(req.ctx)
}
// Load the membership states required to notify users correctly.
func (n *Notifier) Load(ctx context.Context, db *storage.SyncServerDatasource) error {
roomToUsers, err := db.AllJoinedUsersInRooms(ctx)
if err != nil {
return err
}
n.setUsersJoinedToRooms(roomToUsers)
return nil
}
// CurrentPosition returns the current sync position
func (n *Notifier) CurrentPosition() types.SyncPosition {
n.streamLock.Lock()
defer n.streamLock.Unlock()
return n.currPos
}
// setUsersJoinedToRooms marks the given users as 'joined' to the given rooms, such that new events from
// these rooms will wake the given users /sync requests. This should be called prior to ANY calls to
// OnNewEvent (eg on startup) to prevent racing.
func (n *Notifier) setUsersJoinedToRooms(roomIDToUserIDs map[string][]string) {
// This is just the bulk form of addJoinedUser
for roomID, userIDs := range roomIDToUserIDs {
if _, ok := n.roomIDToJoinedUsers[roomID]; !ok {
n.roomIDToJoinedUsers[roomID] = make(userIDSet)
}
for _, userID := range userIDs {
n.roomIDToJoinedUsers[roomID].add(userID)
}
}
}
func (n *Notifier) wakeupUsers(userIDs []string, newPos types.SyncPosition) {
for _, userID := range userIDs {
stream := n.fetchUserStream(userID, false)
if stream != nil {
stream.Broadcast(newPos) // wake up all goroutines Wait()ing on this stream
}
}
}
// fetchUserStream retrieves a stream unique to the given user. If makeIfNotExists is true,
// a stream will be made for this user if one doesn't exist and it will be returned. This
// function does not wait for data to be available on the stream.
// NB: Callers should have locked the mutex before calling this function.
func (n *Notifier) fetchUserStream(userID string, makeIfNotExists bool) *UserStream {
stream, ok := n.userStreams[userID]
if !ok && makeIfNotExists {
// TODO: Unbounded growth of streams (1 per user)
stream = NewUserStream(userID, n.currPos)
n.userStreams[userID] = stream
}
return stream
}
// Not thread-safe: must be called on the OnNewEvent goroutine only
func (n *Notifier) addJoinedUser(roomID, userID string) {
if _, ok := n.roomIDToJoinedUsers[roomID]; !ok {
n.roomIDToJoinedUsers[roomID] = make(userIDSet)
}
n.roomIDToJoinedUsers[roomID].add(userID)
}
// Not thread-safe: must be called on the OnNewEvent goroutine only
func (n *Notifier) removeJoinedUser(roomID, userID string) {
if _, ok := n.roomIDToJoinedUsers[roomID]; !ok {
n.roomIDToJoinedUsers[roomID] = make(userIDSet)
}
n.roomIDToJoinedUsers[roomID].remove(userID)
}
// Not thread-safe: must be called on the OnNewEvent goroutine only
func (n *Notifier) joinedUsers(roomID string) (userIDs []string) {
if _, ok := n.roomIDToJoinedUsers[roomID]; !ok {
return
}
return n.roomIDToJoinedUsers[roomID].values()
}
// removeEmptyUserStreams iterates through the user stream map and removes any
// that have been empty for a certain amount of time. This is a crude way of
// ensuring that the userStreams map doesn't grow forver.
// This should be called when the notifier gets called for whatever reason,
// the function itself is responsible for ensuring it doesn't iterate too
// often.
// NB: Callers should have locked the mutex before calling this function.
func (n *Notifier) removeEmptyUserStreams() {
// Only clean up now and again
now := time.Now()
if n.lastCleanUpTime.Add(time.Minute).After(now) {
return
}
n.lastCleanUpTime = now
deleteBefore := now.Add(-5 * time.Minute)
for key, value := range n.userStreams {
if value.TimeOfLastNonEmpty().Before(deleteBefore) {
delete(n.userStreams, key)
}
}
}
// A string set, mainly existing for improving clarity of structs in this file.
type userIDSet map[string]bool
func (s userIDSet) add(str string) {
s[str] = true
}
func (s userIDSet) remove(str string) {
delete(s, str)
}
func (s userIDSet) values() (vals []string) {
for str := range s {
vals = append(vals, str)
}
return
}