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/**
* Copyright (C) 2023-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/db/change_collection_truncate_markers.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/change_stream_serverless_helpers.h"
#include "mongo/db/operation_context.h"
namespace mongo {
namespace {
MONGO_FAIL_POINT_DEFINE(injectCurrentWallTimeForCheckingMarkers);
Date_t getWallTimeToUse(OperationContext* opCtx) {
auto now = opCtx->getServiceContext()->getFastClockSource()->now();
injectCurrentWallTimeForCheckingMarkers.execute(
[&](const BSONObj& data) { now = data.getField("currentWallTime").date(); });
return now;
}
bool hasMarkerWallTimeExpired(OperationContext* opCtx,
Date_t markerWallTime,
const TenantId& tenantId) {
auto now = getWallTimeToUse(opCtx);
auto expireAfterSeconds =
Seconds{change_stream_serverless_helpers::getExpireAfterSeconds(tenantId)};
auto expirationTime = now - expireAfterSeconds;
return markerWallTime <= expirationTime;
}
} // namespace
ChangeCollectionTruncateMarkers::ChangeCollectionTruncateMarkers(TenantId tenantId,
std::deque<Marker> markers,
int64_t leftoverRecordsCount,
int64_t leftoverRecordsBytes,
int64_t minBytesPerMarker)
: CollectionTruncateMarkersWithPartialExpiration(
std::move(markers), leftoverRecordsCount, leftoverRecordsBytes, minBytesPerMarker),
_tenantId(std::move(tenantId)) {}
bool ChangeCollectionTruncateMarkers::_hasExcessMarkers(OperationContext* opCtx) const {
const auto& markers = getMarkers();
if (markers.empty()) {
// If there's nothing in the markers queue then we don't have excess markers by definition.
return false;
}
const Marker& oldestMarker = markers.front();
const auto& [highestRecordIdInserted, _] = getPartialMarker();
if (highestRecordIdInserted <= oldestMarker.lastRecord) {
// We cannot expire the marker when the last entry is present there as it would break the
// requirement of always having at least 1 entry present in the collection.
return false;
}
return hasMarkerWallTimeExpired(opCtx, oldestMarker.wallTime, _tenantId);
}
bool ChangeCollectionTruncateMarkers::_hasPartialMarkerExpired(OperationContext* opCtx) const {
const auto& [_, highestSeenWallTime] = getPartialMarker();
return hasMarkerWallTimeExpired(opCtx, highestSeenWallTime, _tenantId);
}
void ChangeCollectionTruncateMarkers::expirePartialMarker(OperationContext* opCtx,
const Collection* changeCollection) {
createPartialMarkerIfNecessary(opCtx);
// We can't use the normal peekOldestMarkerIfNeeded method since that calls _hasExcessMarkers
// and it will return false since the new oldest marker will have the last entry.
auto oldestMarker =
checkMarkersWith([&](const std::deque<CollectionTruncateMarkers::Marker>& markers)
-> boost::optional<CollectionTruncateMarkers::Marker> {
// Partial marker did not get generated, early exit.
if (markers.empty()) {
return {};
}
auto firstMarker = markers.front();
// We will only consider the case of an expired marker.
if (!hasMarkerWallTimeExpired(opCtx, firstMarker.wallTime, _tenantId)) {
return {};
}
return firstMarker;
});
if (!oldestMarker) {
// The oldest marker hasn't expired, nothing to do here.
return;
}
// Abandon the snapshot so we can fetch the most recent version of the table. This increases the
// chances the last entry isn't present in the new partial marker.
opCtx->recoveryUnit()->abandonSnapshot();
WriteUnitOfWork wuow(opCtx);
auto backCursor = changeCollection->getRecordStore()->getCursor(opCtx, false);
// If the oldest marker does not contain the last entry it's a normal marker, don't perform any
// modifications to it.
auto obj = backCursor->next();
if (!obj || obj->id > oldestMarker->lastRecord) {
return;
}
// At this point the marker contains the last entry of the collection, we have to shift the last
// entry to the next marker so we can expire the previous entries.
auto bytesNotTruncated = obj->data.size();
const auto& doc = obj->data.toBson();
auto wallTime = doc[repl::OplogEntry::kWallClockTimeFieldName].Date();
updateCurrentMarkerAfterInsertOnCommit(opCtx, bytesNotTruncated, obj->id, wallTime, 1);
auto bytesDeleted = oldestMarker->bytes - bytesNotTruncated;
auto docsDeleted = oldestMarker->records - 1;
// We build the previous record id based on the extracted value
auto previousRecordId = [&] {
auto currId = doc[repl::OplogEntry::k_idFieldName].timestamp();
invariant(currId > Timestamp::min(), "Last entry timestamp must be larger than 0");
auto fixedBson = BSON(repl::OplogEntry::k_idFieldName << (currId - 1));
auto recordId = invariantStatusOK(
record_id_helpers::keyForDoc(fixedBson,
changeCollection->getClusteredInfo()->getIndexSpec(),
changeCollection->getDefaultCollator()));
return recordId;
}();
auto newMarker =
CollectionTruncateMarkers::Marker{docsDeleted, bytesDeleted, previousRecordId, wallTime};
// Replace now the oldest marker with a version that doesn't contain the last entry. This is
// susceptible to races with concurrent inserts. But the invariant of metrics being correct in
// aggregate still holds. Ignoring this issue is a valid strategy here as we move the ignored
// bytes to the next partial marker and we only guarantee eventual correctness.
modifyMarkersWith([&](std::deque<CollectionTruncateMarkers::Marker>& markers) {
markers.pop_front();
markers.emplace_front(std::move(newMarker));
});
wuow.commit();
}
} // namespace mongo
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