Handle sync ordering vs back-fill ordering (see synapse #7164) resulting in dupe events

Also extra robustness while filling a gap

ignore duplicate events from synapse instead considering them an
overlapping event with the adjacent fragment
This commit is contained in:
Bruno Windels 2020-03-28 16:14:48 +01:00
parent 9b2f282534
commit 73ea09f668
3 changed files with 85 additions and 18 deletions

View File

@ -17,6 +17,10 @@ export default class Direction {
return this.isForward ? "f" : "b";
}
reverse() {
return this.isForward ? Direction.Backward : Direction.Forward
}
static get Forward() {
return _forward;
}

View File

@ -37,7 +37,11 @@ export default class EventKey {
}
static get defaultLiveKey() {
return new EventKey(Platform.minStorageKey, Platform.middleStorageKey);
return EventKey.defaultFragmentKey(Platform.minStorageKey);
}
static defaultFragmentKey(fragmentId) {
return new EventKey(fragmentId, Platform.middleStorageKey);
}
toString() {

View File

@ -10,30 +10,75 @@ export default class GapWriter {
}
// events is in reverse-chronological order (last event comes at index 0) if backwards
async _findOverlappingEvents(fragmentEntry, events, txn) {
const eventIds = events.map(e => e.event_id);
let nonOverlappingEvents = events;
let expectedOverlappingEventId;
if (fragmentEntry.hasLinkedFragment) {
expectedOverlappingEventId = await this._findExpectedOverlappingEventId(fragmentEntry, txn);
}
let remainingEvents = events;
let nonOverlappingEvents = [];
let neighbourFragmentEntry;
const neighbourEventId = await txn.timelineEvents.findFirstOccurringEventId(this._roomId, eventIds);
if (neighbourEventId) {
// trim overlapping events
const neighbourEventIndex = events.findIndex(e => e.event_id === neighbourEventId);
nonOverlappingEvents = events.slice(0, neighbourEventIndex);
// get neighbour fragment to link it up later on
const neighbourEvent = await txn.timelineEvents.getByEventId(this._roomId, neighbourEventId);
const neighbourFragment = await txn.timelineFragments.get(this._roomId, neighbourEvent.fragmentId);
neighbourFragmentEntry = fragmentEntry.createNeighbourEntry(neighbourFragment);
while (remainingEvents && remainingEvents.length) {
const eventIds = remainingEvents.map(e => e.event_id);
const duplicateEventId = await txn.timelineEvents.findFirstOccurringEventId(this._roomId, eventIds);
if (duplicateEventId) {
const duplicateEventIndex = remainingEvents.findIndex(e => e.event_id === duplicateEventId);
// should never happen, just being defensive as this *can't* go wrong
if (duplicateEventIndex === -1) {
throw new Error(`findFirstOccurringEventId returned ${duplicateEventIndex} which wasn't ` +
`in [${eventIds.join(",")}] in ${this._roomId}`);
}
nonOverlappingEvents.push(...remainingEvents.slice(0, duplicateEventIndex));
if (!expectedOverlappingEventId || duplicateEventId === expectedOverlappingEventId) {
// TODO: check here that the neighbourEvent is at the correct edge of it's fragment
// get neighbour fragment to link it up later on
const neighbourEvent = await txn.timelineEvents.getByEventId(this._roomId, duplicateEventId);
const neighbourFragment = await txn.timelineFragments.get(this._roomId, neighbourEvent.fragmentId);
neighbourFragmentEntry = fragmentEntry.createNeighbourEntry(neighbourFragment);
// trim overlapping events
remainingEvents = null;
} else {
// we've hit https://github.com/matrix-org/synapse/issues/7164,
// e.g. the event id we found is already in our store but it is not
// the adjacent fragment id. Ignore the event, but keep processing the ones after.
remainingEvents = remainingEvents.slice(duplicateEventIndex + 1);
}
} else {
nonOverlappingEvents.push(...remainingEvents);
remainingEvents = null;
}
}
return {nonOverlappingEvents, neighbourFragmentEntry};
}
async _findLastFragmentEventKey(fragmentEntry, txn) {
async _findExpectedOverlappingEventId(fragmentEntry, txn) {
const eventEntry = await this._findFragmentEdgeEvent(
fragmentEntry.linkedFragmentId,
// reverse because it's the oppose edge of the linked fragment
fragmentEntry.direction.reverse(),
txn);
if (eventEntry) {
return eventEntry.event.event_id;
}
}
async _findFragmentEdgeEventKey(fragmentEntry, txn) {
const {fragmentId, direction} = fragmentEntry;
const event = await this._findFragmentEdgeEvent(fragmentId, direction, txn);
if (event) {
return new EventKey(event.fragmentId, event.eventIndex);
} else {
// no events yet in the fragment ... odd, but let's not fail and take the default key
return EventKey.defaultFragmentKey(fragmentEntry.fragmentId);
}
}
async _findFragmentEdgeEvent(fragmentId, direction, txn) {
if (direction.isBackward) {
const [firstEvent] = await txn.timelineEvents.firstEvents(this._roomId, fragmentId, 1);
return new EventKey(firstEvent.fragmentId, firstEvent.eventIndex);
return firstEvent;
} else {
const [lastEvent] = await txn.timelineEvents.lastEvents(this._roomId, fragmentId, 1);
return new EventKey(lastEvent.fragmentId, lastEvent.eventIndex);
return lastEvent;
}
}
@ -57,8 +102,22 @@ export default class GapWriter {
directionalAppend(entries, fragmentEntry, direction);
// set `end` as token, and if we found an event in the step before, link up the fragments in the fragment entry
if (neighbourFragmentEntry) {
fragmentEntry.linkedFragmentId = neighbourFragmentEntry.fragmentId;
neighbourFragmentEntry.linkedFragmentId = fragmentEntry.fragmentId;
// the throws here should never happen and are only here to detect client or unhandled server bugs
// and a last measure to prevent corrupting fragment links
if (!fragmentEntry.hasLinkedFragment) {
fragmentEntry.linkedFragmentId = neighbourFragmentEntry.fragmentId;
} else if (fragmentEntry.linkedFragmentId !== neighbourFragmentEntry.fragmentId) {
throw new Error(`Prevented changing fragment ${fragmentEntry.fragmentId} ` +
`${fragmentEntry.direction.asApiString()} link from ${fragmentEntry.linkedFragmentId} ` +
`to ${neighbourFragmentEntry.fragmentId} in ${this._roomId}`);
}
if (!neighbourFragmentEntry.hasLinkedFragment) {
neighbourFragmentEntry.linkedFragmentId = fragmentEntry.fragmentId;
} else if (neighbourFragmentEntry.linkedFragmentId !== fragmentEntry.fragmentId) {
throw new Error(`Prevented changing fragment ${neighbourFragmentEntry.fragmentId} ` +
`${neighbourFragmentEntry.direction.asApiString()} link from ${neighbourFragmentEntry.linkedFragmentId} ` +
`to ${fragmentEntry.fragmentId} in ${this._roomId}`);
}
// if neighbourFragmentEntry was found, it means the events were overlapping,
// so no pagination should happen anymore.
neighbourFragmentEntry.token = null;
@ -100,7 +159,7 @@ export default class GapWriter {
throw new Error("start is not equal to prev_batch or next_batch");
}
// find last event in fragment so we get the eventIndex to begin creating keys at
let lastKey = await this._findLastFragmentEventKey(fragmentEntry, txn);
let lastKey = await this._findFragmentEdgeEventKey(fragmentEntry, txn);
// find out if any event in chunk is already present using findFirstOrLastOccurringEventId
const {
nonOverlappingEvents,