dendrite/roomserver/internal/input/input_latest_events.go

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// Copyright 2017 Vector Creations Ltd
// Copyright 2018 New Vector Ltd
// Copyright 2019-2020 The Matrix.org Foundation C.I.C.
//
// 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 input
import (
"context"
"fmt"
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"github.com/getsentry/sentry-go"
"github.com/matrix-org/gomatrixserverlib"
"github.com/matrix-org/util"
"github.com/sirupsen/logrus"
"github.com/matrix-org/dendrite/internal"
"github.com/matrix-org/dendrite/internal/sqlutil"
"github.com/matrix-org/dendrite/roomserver/api"
"github.com/matrix-org/dendrite/roomserver/state"
"github.com/matrix-org/dendrite/roomserver/storage/shared"
"github.com/matrix-org/dendrite/roomserver/types"
)
// updateLatestEvents updates the list of latest events for this room in the database and writes the
// event to the output log.
// The latest events are the events that aren't referenced by another event in the database:
//
// Time goes down the page. 1 is the m.room.create event (root).
// 1 After storing 1 the latest events are {1}
// | After storing 2 the latest events are {2}
// 2 After storing 3 the latest events are {3}
// / \ After storing 4 the latest events are {3,4}
// 3 4 After storing 5 the latest events are {5,4}
// | | After storing 6 the latest events are {5,6}
// 5 6 <--- latest After storing 7 the latest events are {6,7}
// |
// 7 <----- latest
//
// Can only be called once at a time
func (r *Inputer) updateLatestEvents(
ctx context.Context,
roomInfo *types.RoomInfo,
stateAtEvent types.StateAtEvent,
event gomatrixserverlib.PDU,
sendAsServer string,
transactionID *api.TransactionID,
rewritesState bool,
historyVisibility gomatrixserverlib.HistoryVisibility,
) (err error) {
trace, ctx := internal.StartRegion(ctx, "updateLatestEvents")
defer trace.EndRegion()
var succeeded bool
updater, err := r.DB.GetRoomUpdater(ctx, roomInfo)
if err != nil {
return fmt.Errorf("r.DB.GetRoomUpdater: %w", err)
}
defer sqlutil.EndTransactionWithCheck(updater, &succeeded, &err)
u := latestEventsUpdater{
ctx: ctx,
api: r,
updater: updater,
roomInfo: roomInfo,
stateAtEvent: stateAtEvent,
event: event,
sendAsServer: sendAsServer,
transactionID: transactionID,
rewritesState: rewritesState,
historyVisibility: historyVisibility,
}
if err = u.doUpdateLatestEvents(); err != nil {
return fmt.Errorf("u.doUpdateLatestEvents: %w", err)
}
succeeded = true
return
}
// latestEventsUpdater tracks the state used to update the latest events in the
// room. It mostly just ferries state between the various function calls.
// The state could be passed using function arguments, but it becomes impractical
// when there are so many variables to pass around.
type latestEventsUpdater struct {
ctx context.Context
api *Inputer
updater *shared.RoomUpdater
roomInfo *types.RoomInfo
stateAtEvent types.StateAtEvent
event gomatrixserverlib.PDU
transactionID *api.TransactionID
rewritesState bool
// Which server to send this event as.
sendAsServer string
// The eventID of the event that was processed before this one.
lastEventIDSent string
// The latest events in the room after processing this event.
oldLatest types.StateAtEventAndReferences
latest types.StateAtEventAndReferences
// The state entries removed from and added to the current state of the
// room as a result of processing this event. They are sorted lists.
removed []types.StateEntry
added []types.StateEntry
// The state entries that are removed and added to recover the state before
// the event being processed. They are sorted lists.
stateBeforeEventRemoves []types.StateEntry
stateBeforeEventAdds []types.StateEntry
// The snapshots of current state before and after processing this event
oldStateNID types.StateSnapshotNID
newStateNID types.StateSnapshotNID
// The history visibility of the event itself (from the state before the event).
historyVisibility gomatrixserverlib.HistoryVisibility
}
func (u *latestEventsUpdater) doUpdateLatestEvents() error {
u.lastEventIDSent = u.updater.LastEventIDSent()
// If we are doing a regular event update then we will get the
// previous latest events to use as a part of the calculation. If
// we are overwriting the latest events because we have a complete
// state snapshot from somewhere else, e.g. a federated room join,
// then start with an empty set - none of the forward extremities
// that we knew about before matter anymore.
u.oldLatest = types.StateAtEventAndReferences{}
if !u.rewritesState {
u.oldStateNID = u.updater.CurrentStateSnapshotNID()
u.oldLatest = u.updater.LatestEvents()
}
// If the event has already been written to the output log then we
// don't need to do anything, as we've handled it already.
if hasBeenSent, err := u.updater.HasEventBeenSent(u.stateAtEvent.EventNID); err != nil {
return fmt.Errorf("u.updater.HasEventBeenSent: %w", err)
} else if hasBeenSent {
return nil
}
// Work out what the latest events are. This will include the new
// event if it is not already referenced.
extremitiesChanged, err := u.calculateLatest(
u.oldLatest, u.event,
types.StateAtEventAndReference{
EventID: u.event.EventID(),
StateAtEvent: u.stateAtEvent,
},
)
if err != nil {
return fmt.Errorf("u.calculateLatest: %w", err)
}
// Now that we know what the latest events are, it's time to get the
// latest state.
var updates []api.OutputEvent
if extremitiesChanged || u.rewritesState {
if err = u.latestState(); err != nil {
return fmt.Errorf("u.latestState: %w", err)
}
// If we need to generate any output events then here's where we do it.
// TODO: Move this!
if updates, err = u.api.updateMemberships(u.ctx, u.updater, u.removed, u.added); err != nil {
return fmt.Errorf("u.api.updateMemberships: %w", err)
}
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} else {
u.newStateNID = u.oldStateNID
}
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if err = u.updater.SetLatestEvents(u.roomInfo.RoomNID, u.latest, u.stateAtEvent.EventNID, u.newStateNID); err != nil {
return fmt.Errorf("u.updater.SetLatestEvents: %w", err)
}
update, err := u.makeOutputNewRoomEvent()
if err != nil {
return fmt.Errorf("u.makeOutputNewRoomEvent: %w", err)
}
updates = append(updates, *update)
// Send the event to the output logs.
// We do this inside the database transaction to ensure that we only mark an event as sent if we sent it.
// (n.b. this means that it's possible that the same event will be sent twice if the transaction fails but
// the write to the output log succeeds)
// TODO: This assumes that writing the event to the output log is synchronous. It should be possible to
// send the event asynchronously but we would need to ensure that 1) the events are written to the log in
// the correct order, 2) that pending writes are resent across restarts. In order to avoid writing all the
// necessary bookkeeping we'll keep the event sending synchronous for now.
if err = u.api.OutputProducer.ProduceRoomEvents(u.event.RoomID().String(), updates); err != nil {
return fmt.Errorf("u.api.WriteOutputEvents: %w", err)
}
if err = u.updater.MarkEventAsSent(u.stateAtEvent.EventNID); err != nil {
return fmt.Errorf("u.updater.MarkEventAsSent: %w", err)
}
return nil
}
func (u *latestEventsUpdater) latestState() error {
trace, ctx := internal.StartRegion(u.ctx, "processEventWithMissingState")
defer trace.EndRegion()
var err error
roomState := state.NewStateResolution(u.updater, u.roomInfo, u.api.Queryer)
// Work out if the state at the extremities has actually changed
// or not. If they haven't then we won't bother doing all of the
// hard work.
if !u.stateAtEvent.IsStateEvent() {
stateChanged := false
oldStateNIDs := make([]types.StateSnapshotNID, 0, len(u.oldLatest))
newStateNIDs := make([]types.StateSnapshotNID, 0, len(u.latest))
for _, old := range u.oldLatest {
oldStateNIDs = append(oldStateNIDs, old.BeforeStateSnapshotNID)
}
for _, new := range u.latest {
newStateNIDs = append(newStateNIDs, new.BeforeStateSnapshotNID)
}
oldStateNIDs = state.UniqueStateSnapshotNIDs(oldStateNIDs)
newStateNIDs = state.UniqueStateSnapshotNIDs(newStateNIDs)
if len(oldStateNIDs) != len(newStateNIDs) {
stateChanged = true
} else {
for i := range oldStateNIDs {
if oldStateNIDs[i] != newStateNIDs[i] {
stateChanged = true
break
}
}
}
if !stateChanged {
u.newStateNID = u.oldStateNID
return nil
}
}
// Get a list of the current latest events. This may or may not
// include the new event from the input path, depending on whether
// it is a forward extremity or not.
latestStateAtEvents := make([]types.StateAtEvent, len(u.latest))
for i := range u.latest {
latestStateAtEvents[i] = u.latest[i].StateAtEvent
}
// Takes the NIDs of the latest events and creates a state snapshot
// of the state after the events. The snapshot state will be resolved
// using the correct state resolution algorithm for the room.
u.newStateNID, err = roomState.CalculateAndStoreStateAfterEvents(
ctx, latestStateAtEvents,
)
if err != nil {
return fmt.Errorf("roomState.CalculateAndStoreStateAfterEvents: %w", err)
}
// Include information about what changed in the state transition. If the
// event rewrites the state (i.e. is a federated join) then we will simply
// include the entire state snapshot as added events, as the "RewritesState"
// flag in the output event signals downstream components to purge their
// room state first. If it doesn't rewrite the state then we will work out
// what the difference is between the state snapshots and send that. In all
// cases where a state event is being replaced, the old state event will
// appear in "removed" and the replacement will appear in "added".
if u.rewritesState {
u.removed = []types.StateEntry{}
u.added, err = roomState.LoadStateAtSnapshot(ctx, u.newStateNID)
if err != nil {
return fmt.Errorf("roomState.LoadStateAtSnapshot: %w", err)
}
} else {
u.removed, u.added, err = roomState.DifferenceBetweeenStateSnapshots(
ctx, u.oldStateNID, u.newStateNID,
)
if err != nil {
return fmt.Errorf("roomState.DifferenceBetweenStateSnapshots: %w", err)
}
}
if removed := len(u.removed) - len(u.added); !u.rewritesState && removed > 0 {
logrus.WithFields(logrus.Fields{
"event_id": u.event.EventID(),
"room_id": u.event.RoomID().String(),
"old_state_nid": u.oldStateNID,
"new_state_nid": u.newStateNID,
"old_latest": u.oldLatest.EventIDs(),
"new_latest": u.latest.EventIDs(),
}).Warnf("State reset detected (removing %d events)", removed)
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sentry.WithScope(func(scope *sentry.Scope) {
scope.SetLevel("warning")
scope.SetTag("room_id", u.event.RoomID().String())
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scope.SetContext("State reset", map[string]interface{}{
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"Event ID": u.event.EventID(),
"Old state NID": fmt.Sprintf("%d", u.oldStateNID),
"New state NID": fmt.Sprintf("%d", u.newStateNID),
"Old latest": u.oldLatest.EventIDs(),
"New latest": u.latest.EventIDs(),
"State removed": removed,
})
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sentry.CaptureMessage("State reset detected")
})
}
// Also work out the state before the event removes and the event
// adds.
u.stateBeforeEventRemoves, u.stateBeforeEventAdds, err = roomState.DifferenceBetweeenStateSnapshots(
ctx, u.newStateNID, u.stateAtEvent.BeforeStateSnapshotNID,
)
if err != nil {
return fmt.Errorf("roomState.DifferenceBetweeenStateSnapshots: %w", err)
}
return nil
}
// calculateLatest works out the new set of forward extremities. Returns
// true if the new event is included in those extremites, false otherwise.
func (u *latestEventsUpdater) calculateLatest(
oldLatest []types.StateAtEventAndReference,
newEvent gomatrixserverlib.PDU,
newStateAndRef types.StateAtEventAndReference,
) (bool, error) {
trace, _ := internal.StartRegion(u.ctx, "calculateLatest")
defer trace.EndRegion()
// First of all, get a list of all of the events in our current
// set of forward extremities.
existingRefs := make(map[string]*types.StateAtEventAndReference)
for i, old := range oldLatest {
existingRefs[old.EventID] = &oldLatest[i]
}
// If the "new" event is already a forward extremity then stop, as
// nothing changes.
if _, ok := existingRefs[newEvent.EventID()]; ok {
u.latest = oldLatest
return false, nil
}
// If the "new" event is already referenced by an existing event
// then do nothing - it's not a candidate to be a new extremity if
// it has been referenced.
if referenced, err := u.updater.IsReferenced(newEvent.EventID()); err != nil {
return false, fmt.Errorf("u.updater.IsReferenced(new): %w", err)
} else if referenced {
u.latest = oldLatest
return false, nil
}
// Then let's see if any of the existing forward extremities now
// have entries in the previous events table. If they do then we
// will no longer include them as forward extremities.
for k, l := range existingRefs {
referenced, err := u.updater.IsReferenced(l.EventID)
if err != nil {
return false, fmt.Errorf("u.updater.IsReferenced: %w", err)
} else if referenced {
delete(existingRefs, k)
}
}
// Start off with our new unreferenced event. We're reusing the backing
// array here rather than allocating a new one.
u.latest = append(u.latest[:0], newStateAndRef)
// If our new event references any of the existing forward extremities
// then they are no longer forward extremities, so remove them.
for _, prevEventID := range newEvent.PrevEventIDs() {
delete(existingRefs, prevEventID)
}
// Then re-add any old extremities that are still valid after all.
for _, old := range existingRefs {
u.latest = append(u.latest, *old)
}
return true, nil
}
func (u *latestEventsUpdater) makeOutputNewRoomEvent() (*api.OutputEvent, error) {
latestEventIDs := make([]string, len(u.latest))
for i := range u.latest {
latestEventIDs[i] = u.latest[i].EventID
}
ore := api.OutputNewRoomEvent{
Event: &types.HeaderedEvent{PDU: u.event},
RewritesState: u.rewritesState,
LastSentEventID: u.lastEventIDSent,
LatestEventIDs: latestEventIDs,
TransactionID: u.transactionID,
SendAsServer: u.sendAsServer,
HistoryVisibility: u.historyVisibility,
}
eventIDMap, err := u.stateEventMap()
if err != nil {
return nil, err
}
for _, entry := range u.added {
ore.AddsStateEventIDs = append(ore.AddsStateEventIDs, eventIDMap[entry.EventNID])
}
for _, entry := range u.removed {
ore.RemovesStateEventIDs = append(ore.RemovesStateEventIDs, eventIDMap[entry.EventNID])
}
for _, entry := range u.stateBeforeEventRemoves {
ore.StateBeforeRemovesEventIDs = append(ore.StateBeforeRemovesEventIDs, eventIDMap[entry.EventNID])
}
for _, entry := range u.stateBeforeEventAdds {
ore.StateBeforeAddsEventIDs = append(ore.StateBeforeAddsEventIDs, eventIDMap[entry.EventNID])
}
return &api.OutputEvent{
Type: api.OutputTypeNewRoomEvent,
NewRoomEvent: &ore,
}, nil
}
// retrieve an event nid -> event ID map for all events that need updating
func (u *latestEventsUpdater) stateEventMap() (map[types.EventNID]string, error) {
cap := len(u.added) + len(u.removed) + len(u.stateBeforeEventRemoves) + len(u.stateBeforeEventAdds)
stateEventNIDs := make(types.EventNIDs, 0, cap)
allStateEntries := make([]types.StateEntry, 0, cap)
allStateEntries = append(allStateEntries, u.added...)
allStateEntries = append(allStateEntries, u.removed...)
allStateEntries = append(allStateEntries, u.stateBeforeEventRemoves...)
allStateEntries = append(allStateEntries, u.stateBeforeEventAdds...)
for _, entry := range allStateEntries {
stateEventNIDs = append(stateEventNIDs, entry.EventNID)
}
stateEventNIDs = stateEventNIDs[:util.SortAndUnique(stateEventNIDs)]
return u.updater.EventIDs(u.ctx, stateEventNIDs)
}