path: root/src/mongo/db/session_catalog_mongod.cpp

/**
 *    Copyright (C) 2018-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/platform/basic.h"

#include "mongo/db/session_catalog_mongod.h"

#include "mongo/bson/bsonmisc.h"
#include "mongo/db/catalog_raii.h"
#include "mongo/db/client.h"
#include "mongo/db/create_indexes_gen.h"
#include "mongo/db/dbdirectclient.h"
#include "mongo/db/index_builds_coordinator.h"
#include "mongo/db/internal_transactions_feature_flag_gen.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/ops/write_ops.h"
#include "mongo/db/repl/repl_server_parameters_gen.h"
#include "mongo/db/repl/storage_interface_impl.h"
#include "mongo/db/service_context.h"
#include "mongo/db/session_txn_record_gen.h"
#include "mongo/db/sessions_collection.h"
#include "mongo/db/transaction_participant.h"
#include "mongo/logv2/log.h"
#include "mongo/rpc/get_status_from_command_result.h"
#include "mongo/s/transaction_router.h"
#include "mongo/util/concurrency/thread_pool.h"
#include "mongo/util/scopeguard.h"

#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kTransaction


namespace mongo {
namespace {

struct SessionTasksExecutor {
    SessionTasksExecutor()
        : threadPool([] {
              ThreadPool::Options options;
              options.threadNamePrefix = "MongoDSessionCatalog";
              options.minThreads = 0;
              options.maxThreads = 1;
              return options;
          }()) {}

    ThreadPool threadPool;
};

const auto sessionTasksExecutor = ServiceContext::declareDecoration<SessionTasksExecutor>();
const ServiceContext::ConstructorActionRegisterer sessionTasksExecutorRegisterer{
    "SessionCatalogD",
    [](ServiceContext* service) { sessionTasksExecutor(service).threadPool.startup(); },
    [](ServiceContext* service) {
        auto& pool = sessionTasksExecutor(service).threadPool;
        pool.shutdown();
        pool.join();
    }};

auto getThreadPool(OperationContext* opCtx) {
    return &sessionTasksExecutor(opCtx->getServiceContext()).threadPool;
}

/**
 * Non-blocking call, which schedules asynchronously the work to finish cleaning up the specified
 * set of kill tokens.
 */
void killSessionTokens(OperationContext* opCtx,
                       std::vector<SessionCatalog::KillToken> sessionKillTokens) {
    if (sessionKillTokens.empty())
        return;

    getThreadPool(opCtx)->schedule(
        [service = opCtx->getServiceContext(),
         sessionKillTokens = std::move(sessionKillTokens)](auto status) mutable {
            invariant(status);

            ThreadClient tc("Kill-Sessions", service);
            auto uniqueOpCtx = tc->makeOperationContext();
            const auto opCtx = uniqueOpCtx.get();
            const auto catalog = SessionCatalog::get(opCtx);

            for (auto& sessionKillToken : sessionKillTokens) {
                auto session = catalog->checkOutSessionForKill(opCtx, std::move(sessionKillToken));
                auto participant = TransactionParticipant::get(session);
                participant.invalidate(opCtx);
            }
        });
}

void disallowDirectWritesUnderSession(OperationContext* opCtx) {
    const auto replCoord = repl::ReplicationCoordinator::get(opCtx);
    bool isReplSet = replCoord->getReplicationMode() == repl::ReplicationCoordinator::modeReplSet;
    if (isReplSet) {
        uassert(40528,
                str::stream() << "Direct writes against "
                              << NamespaceString::kSessionTransactionsTableNamespace
                              << " cannot be performed using a transaction or on a session.",
                !opCtx->getLogicalSessionId());
    }
}

/**
 * Removes the transaction sessions that are expired and not in use from the in-memory catalog
 * (i.e. SessionCatalog). Returns the session ids for the expired transaction sessions that were
 * not removed because they were in use.
 */
LogicalSessionIdSet removeExpiredTransactionSessionsNotInUseFromMemory(
    OperationContext* opCtx, SessionsCollection& sessionsCollection, Date_t possiblyExpired) {
    const auto catalog = SessionCatalog::get(opCtx);

    // Find the possibly expired logical session ids in the in-memory catalog.
    LogicalSessionIdSet possiblyExpiredLogicalSessionIds;
    // Skip child transaction sessions since they correspond to the same logical session as their
    // parent transaction session so they have the same last check-out time as the parent's.
    catalog->scanParentSessions([&](const ObservableSession& session) {
        const auto sessionId = session.getSessionId();
        invariant(isParentSessionId(sessionId));
        if (session.getLastCheckout() < possiblyExpired) {
            possiblyExpiredLogicalSessionIds.insert(sessionId);
        }
    });
    // From the possibly expired logical session ids, find the ones that have been removed from
    // from the config.system.sessions collection.
    LogicalSessionIdSet expiredLogicalSessionIds =
        sessionsCollection.findRemovedSessions(opCtx, possiblyExpiredLogicalSessionIds);

    // For each removed logical session id, removes all of its transaction session ids that are no
    // longer in use from the in-memory catalog.
    LogicalSessionIdSet expiredTransactionSessionIdsStillInUse;
    for (const auto& expiredLogicalSessionId : expiredLogicalSessionIds) {
        invariant(isParentSessionId(expiredLogicalSessionId));

        // Scan all the transaction sessions for this logical session at once so reaping can be done
        // atomically.
        TxnNumber parentSessionActiveTxnNumber;
        const auto transactionSessionIdsNotReaped = catalog->scanSessionsForReap(
            expiredLogicalSessionId,
            [&](ObservableSession& parentSession) {
                const auto transactionSessionId = parentSession.getSessionId();
                const auto txnParticipant = TransactionParticipant::get(parentSession);
                const auto txnRouter = TransactionRouter::get(parentSession);

                parentSessionActiveTxnNumber =
                    txnParticipant.getActiveTxnNumberAndRetryCounter().getTxnNumber();
                if (txnParticipant.canBeReaped() && txnRouter.canBeReaped()) {
                    LOGV2_DEBUG(6753702,
                                5,
                                "Marking parent transaction session for reap",
                                "lsid"_attr = transactionSessionId);
                    // This is an external session so it can be reaped if and only if all of its
                    // internal sessions can be reaped.
                    parentSession.markForReap(ObservableSession::ReapMode::kNonExclusive);
                }
            },
            [&](ObservableSession& childSession) {
                const auto transactionSessionId = childSession.getSessionId();
                const auto txnParticipant = TransactionParticipant::get(childSession);
                const auto txnRouter = TransactionRouter::get(childSession);

                if (txnParticipant.canBeReaped() && txnRouter.canBeReaped()) {
                    if (isInternalSessionForNonRetryableWrite(transactionSessionId)) {
                        LOGV2_DEBUG(6753703,
                                    5,
                                    "Marking child transaction session for reap",
                                    "lsid"_attr = transactionSessionId);
                        // This is an internal session for a non-retryable write so it can be reaped
                        // independently of the external session that write ran in.
                        childSession.markForReap(ObservableSession::ReapMode::kExclusive);
                    } else if (isInternalSessionForRetryableWrite(transactionSessionId)) {
                        LOGV2_DEBUG(6753704,
                                    5,
                                    "Marking child transaction session for reap",
                                    "lsid"_attr = transactionSessionId);
                        // This is an internal session for a retryable write so it must be reaped
                        // atomically with the external session and internal sessions for that
                        // retryable write, unless the write is no longer active (i.e. there is
                        // already a retryable write or transaction with a higher txnNumber).
                        childSession.markForReap(*transactionSessionId.getTxnNumber() <
                                                         parentSessionActiveTxnNumber
                                                     ? ObservableSession::ReapMode::kExclusive
                                                     : ObservableSession::ReapMode::kNonExclusive);
                    } else {
                        MONGO_UNREACHABLE;
                    }
                }
            });
        expiredTransactionSessionIdsStillInUse.insert(transactionSessionIdsNotReaped.begin(),
                                                      transactionSessionIdsNotReaped.end());
    }

    LOGV2_DEBUG(6753705,
                5,
                "Expired sessions not reaped from the SessionCatalog",
                "lsids"_attr = expiredTransactionSessionIdsStillInUse);

    return expiredTransactionSessionIdsStillInUse;
}

const auto kIdProjection = BSON(SessionTxnRecord::kSessionIdFieldName << 1);
const auto kSortById = BSON(SessionTxnRecord::kSessionIdFieldName << 1);
const auto kLastWriteDateFieldName = SessionTxnRecord::kLastWriteDateFieldName;

template <typename SessionContainer>
int removeSessionsTransactionRecordsFromDisk(OperationContext* opCtx,
                                             const SessionContainer& transactionSessionIdsToReap) {
    if (transactionSessionIdsToReap.empty()) {
        return 0;
    }

    // Remove the config.image_collection entries for the expired transaction session ids. We first
    // delete any images belonging to sessions about to be reaped, followed by the sessions. This
    // way if there's a failure, we'll only be left with sessions that have a dangling reference
    // to an image. Session reaping will rediscover the sessions to delete and try again.
    //
    // We opt for this rather than performing the two sets of deletes in a single transaction simply
    // to reduce code complexity.
    DBDirectClient client(opCtx);
    write_ops::checkWriteErrors(client.remove([&] {
        write_ops::DeleteCommandRequest imageDeleteOp(NamespaceString::kConfigImagesNamespace);
        imageDeleteOp.setWriteCommandRequestBase([] {
            write_ops::WriteCommandRequestBase base;
            base.setOrdered(false);
            return base;
        }());
        imageDeleteOp.setDeletes([&] {
            std::vector<write_ops::DeleteOpEntry> entries;
            for (const auto& transactionSessionId : transactionSessionIdsToReap) {
                entries.emplace_back(
                    BSON(LogicalSessionRecord::kIdFieldName << transactionSessionId.toBSON()),
                    false /* multi = false */);
            }
            return entries;
        }());
        return imageDeleteOp;
    }()));

    // Remove the config.transaction entries for the expired transaction session ids.
    auto sessionDeleteReply = write_ops::checkWriteErrors(client.remove([&] {
        write_ops::DeleteCommandRequest sessionDeleteOp(
            NamespaceString::kSessionTransactionsTableNamespace);
        sessionDeleteOp.setWriteCommandRequestBase([] {
            write_ops::WriteCommandRequestBase base;
            base.setOrdered(false);
            return base;
        }());
        sessionDeleteOp.setDeletes([&] {
            std::vector<write_ops::DeleteOpEntry> entries;
            for (const auto& transactionSessionId : transactionSessionIdsToReap) {
                entries.emplace_back(
                    BSON(LogicalSessionRecord::kIdFieldName << transactionSessionId.toBSON()),
                    false /* multi = false */);
            }
            return entries;
        }());
        return sessionDeleteOp;
    }()));

    return sessionDeleteReply.getN();
}

/**
 * Removes the config.transactions and the config.image_collection entries for the transaction
 * sessions in 'expiredTransactionSessionIdsNotInUse' whose logical sessions have expired. Returns
 * the number of transaction sessions whose entries were removed.
 */
int removeSessionsTransactionRecordsIfExpired(
    OperationContext* opCtx,
    SessionsCollection& sessionsCollection,
    const LogicalSessionIdSet& expiredTransactionSessionIdsNotInUse) {
    if (expiredTransactionSessionIdsNotInUse.empty()) {
        return 0;
    }

    // From the expired transaction session ids that are no longer in use, find the ones whose
    // logical sessions have been removed from from the config.system.sessions collection.
    LogicalSessionIdSet transactionSessionIdsToReap;
    {
        LogicalSessionIdSet possiblyExpiredLogicalSessionIds;
        for (const auto& transactionSessionId : expiredTransactionSessionIdsNotInUse) {
            const auto logicalSessionId = isParentSessionId(transactionSessionId)
                ? transactionSessionId
                : *getParentSessionId(transactionSessionId);
            possiblyExpiredLogicalSessionIds.insert(std::move(logicalSessionId));
        }
        auto expiredLogicalSessionIds =
            sessionsCollection.findRemovedSessions(opCtx, possiblyExpiredLogicalSessionIds);

        for (const auto& transactionSessionId : expiredTransactionSessionIdsNotInUse) {
            const auto logicalSessionId = isParentSessionId(transactionSessionId)
                ? transactionSessionId
                : *getParentSessionId(transactionSessionId);
            if (expiredLogicalSessionIds.find(logicalSessionId) != expiredLogicalSessionIds.end()) {
                transactionSessionIdsToReap.insert(transactionSessionId);
            }
        }
    }

    return removeSessionsTransactionRecordsFromDisk(opCtx, transactionSessionIdsToReap);
}

/**
 * Removes the transaction sessions that are expired and not in use from the on-disk catalog (i.e.
 * the config.transactions collection and the config.image_collection collection). Returns the
 * number of transaction sessions whose entries were removed.
 */
int removeExpiredTransactionSessionsFromDisk(
    OperationContext* opCtx,
    SessionsCollection& sessionsCollection,
    Date_t possiblyExpired,
    const LogicalSessionIdSet& expiredTransactionSessionIdsStillInUse) {
    // Scan for records older than the minimum lifetime and uses a sort to walk the '_id' index.
    DBDirectClient client(opCtx);
    FindCommandRequest findRequest{NamespaceString::kSessionTransactionsTableNamespace};
    findRequest.setFilter(BSON(kLastWriteDateFieldName << LT << possiblyExpired));
    findRequest.setSort(kSortById);
    findRequest.setProjection(kIdProjection);
    auto cursor = client.find(std::move(findRequest));

    LogicalSessionIdSet expiredTransactionSessionIdsNotInUse;
    int numReaped = 0;
    while (cursor->more()) {
        auto transactionSession = SessionsCollectionFetchResultIndividualResult::parse(
            "TransactionSession"_sd, cursor->next());
        const auto transactionSessionId = transactionSession.get_id();

        if (expiredTransactionSessionIdsStillInUse.find(transactionSessionId) !=
            expiredTransactionSessionIdsStillInUse.end()) {
            continue;
        }

        expiredTransactionSessionIdsNotInUse.insert(transactionSessionId);
        if (expiredTransactionSessionIdsNotInUse.size() >
            MongoDSessionCatalog::kMaxSessionDeletionBatchSize) {
            numReaped += removeSessionsTransactionRecordsIfExpired(
                opCtx, sessionsCollection, expiredTransactionSessionIdsNotInUse);
            expiredTransactionSessionIdsNotInUse.clear();
        }
    }
    numReaped += removeSessionsTransactionRecordsIfExpired(
        opCtx, sessionsCollection, expiredTransactionSessionIdsNotInUse);

    return numReaped;
}

void createTransactionTable(OperationContext* opCtx) {
    CollectionOptions options;
    auto storageInterface = repl::StorageInterface::get(opCtx);
    auto createCollectionStatus = storageInterface->createCollection(
        opCtx, NamespaceString::kSessionTransactionsTableNamespace, options);

    if (createCollectionStatus == ErrorCodes::NamespaceExists) {
        bool collectionIsEmpty = false;
        {
            AutoGetCollection autoColl(
                opCtx, NamespaceString::kSessionTransactionsTableNamespace, LockMode::MODE_IS);
            invariant(autoColl);

            if (autoColl->getIndexCatalog()->findIndexByName(
                    opCtx, MongoDSessionCatalog::kConfigTxnsPartialIndexName)) {
                // Index already exists, so there's nothing to do.
                return;
            }

            collectionIsEmpty = autoColl->isEmpty(opCtx);
        }

        if (!collectionIsEmpty) {
            // Unless explicitly enabled, don't create the index to avoid delaying step up.
            if (feature_flags::gFeatureFlagAlwaysCreateConfigTransactionsPartialIndexOnStepUp
                    .isEnabledAndIgnoreFCV()) {
                AutoGetCollection autoColl(
                    opCtx, NamespaceString::kSessionTransactionsTableNamespace, LockMode::MODE_X);
                IndexBuildsCoordinator::get(opCtx)->createIndex(
                    opCtx,
                    autoColl->uuid(),
                    MongoDSessionCatalog::getConfigTxnPartialIndexSpec(),
                    IndexBuildsManager::IndexConstraints::kEnforce,
                    false /* fromMigration */);
            }

            return;
        }

        // The index does not exist and the collection is empty, so fall through to create it on the
        // empty collection. This can happen after a failover because the collection and index
        // creation are recorded as separate oplog entries.
    } else {
        uassertStatusOKWithContext(createCollectionStatus,
                                   str::stream()
                                       << "Failed to create the "
                                       << NamespaceString::kSessionTransactionsTableNamespace.ns()
                                       << " collection");
    }

    auto indexSpec = MongoDSessionCatalog::getConfigTxnPartialIndexSpec();

    const auto createIndexStatus = storageInterface->createIndexesOnEmptyCollection(
        opCtx, NamespaceString::kSessionTransactionsTableNamespace, {indexSpec});
    uassertStatusOKWithContext(
        createIndexStatus,
        str::stream() << "Failed to create partial index for the "
                      << NamespaceString::kSessionTransactionsTableNamespace.ns() << " collection");
}

void createRetryableFindAndModifyTable(OperationContext* opCtx) {
    auto serviceCtx = opCtx->getServiceContext();
    CollectionOptions options;
    auto status = repl::StorageInterface::get(serviceCtx)
                      ->createCollection(opCtx, NamespaceString::kConfigImagesNamespace, options);
    if (status == ErrorCodes::NamespaceExists) {
        return;
    }

    uassertStatusOKWithContext(status,
                               str::stream() << "Failed to create the "
                                             << NamespaceString::kConfigImagesNamespace.ns()
                                             << " collection");
}


void abortInProgressTransactions(OperationContext* opCtx) {
    DBDirectClient client(opCtx);
    FindCommandRequest findRequest{NamespaceString::kSessionTransactionsTableNamespace};
    findRequest.setFilter(BSON(SessionTxnRecord::kStateFieldName
                               << DurableTxnState_serializer(DurableTxnStateEnum::kInProgress)));
    auto cursor = client.find(std::move(findRequest));

    if (cursor->more()) {
        LOGV2_DEBUG(21977, 3, "Aborting in-progress transactions on stepup.");
    }
    while (cursor->more()) {
        auto txnRecord = SessionTxnRecord::parse(
            IDLParserErrorContext("abort-in-progress-transactions"), cursor->next());
        opCtx->setLogicalSessionId(txnRecord.getSessionId());
        opCtx->setTxnNumber(txnRecord.getTxnNum());
        opCtx->setInMultiDocumentTransaction();
        MongoDOperationContextSessionWithoutRefresh ocs(opCtx);
        auto txnParticipant = TransactionParticipant::get(opCtx);
        LOGV2_DEBUG(21978,
                    3,
                    "Aborting transaction sessionId: {sessionId} txnNumber {txnNumber}",
                    "Aborting transaction",
                    "sessionId"_attr = txnRecord.getSessionId().toBSON(),
                    "txnNumber"_attr = txnRecord.getTxnNum());
        txnParticipant.abortTransaction(opCtx);
        opCtx->resetMultiDocumentTransactionState();
    }
}
}  // namespace

const std::string MongoDSessionCatalog::kConfigTxnsPartialIndexName = "parent_lsid";

BSONObj MongoDSessionCatalog::getConfigTxnPartialIndexSpec() {
    NewIndexSpec index;
    index.setV(int(IndexDescriptor::kLatestIndexVersion));
    index.setKey(BSON(
        SessionTxnRecord::kParentSessionIdFieldName
        << 1
        << (SessionTxnRecord::kSessionIdFieldName + "." + LogicalSessionId::kTxnNumberFieldName)
        << 1 << SessionTxnRecord::kSessionIdFieldName << 1));
    index.setName(MongoDSessionCatalog::kConfigTxnsPartialIndexName);
    index.setPartialFilterExpression(BSON("parentLsid" << BSON("$exists" << true)));
    return index.toBSON();
}

void MongoDSessionCatalog::onStepUp(OperationContext* opCtx) {
    // Invalidate sessions that could have a retryable write on it, so that we can refresh from disk
    // in case the in-memory state was out of sync.
    const auto catalog = SessionCatalog::get(opCtx);

    std::vector<SessionCatalog::KillToken> sessionKillTokens;

    // Scan all sessions and reacquire locks for prepared transactions.
    // There may be sessions that are checked out during this scan, but none of them
    // can be prepared transactions, since only oplog application can make transactions
    // prepared on secondaries and oplog application has been stopped at this moment.
    std::vector<OperationSessionInfo> sessionsToReacquireLocks;

    SessionKiller::Matcher matcher(
        KillAllSessionsByPatternSet{makeKillAllSessionsByPattern(opCtx)});
    catalog->scanSessions(matcher, [&](const ObservableSession& session) {
        const auto txnParticipant = TransactionParticipant::get(session);
        if (!txnParticipant.transactionIsOpen()) {
            sessionKillTokens.emplace_back(session.kill());
        }

        if (txnParticipant.transactionIsPrepared()) {
            const auto txnNumberAndRetryCounter =
                txnParticipant.getActiveTxnNumberAndRetryCounter();

            OperationSessionInfo sessionInfo;
            sessionInfo.setSessionId(session.getSessionId());
            sessionInfo.setTxnNumber(txnNumberAndRetryCounter.getTxnNumber());
            sessionInfo.setTxnRetryCounter(txnNumberAndRetryCounter.getTxnRetryCounter());
            sessionsToReacquireLocks.emplace_back(sessionInfo);
        }
    });
    killSessionTokens(opCtx, std::move(sessionKillTokens));

    {
        // Create a new opCtx because we need an empty locker to refresh the locks.
        auto newClient = opCtx->getServiceContext()->makeClient("restore-prepared-txn");
        AlternativeClientRegion acr(newClient);
        for (const auto& sessionInfo : sessionsToReacquireLocks) {
            auto newOpCtx = cc().makeOperationContext();
            newOpCtx->setLogicalSessionId(*sessionInfo.getSessionId());
            newOpCtx->setTxnNumber(*sessionInfo.getTxnNumber());
            newOpCtx->setTxnRetryCounter(*sessionInfo.getTxnRetryCounter());
            newOpCtx->setInMultiDocumentTransaction();

            // Use MongoDOperationContextSessionWithoutRefresh to check out the session because:
            // - The in-memory state for this session has been kept in sync with the on-disk state
            //   by secondary oplog application for prepared transactions so no refresh will be
            //   done anyway.
            // - The in-memory state for any external and/or internal sessions associated with this
            //   session may be out-of-date with the on-disk state but no refresh is necessary since
            //   the transaction is already in the prepared state so it no longer needs to go
            //   through conflict and write history check. In addition, a refresh of any session is
            //   expected to cause a deadlock since this 'newOpCtx' will need to acquire the global
            //   lock in the IS mode prior to reading the config.transactions collection but it
            //   cannot do that while the RSTL lock is being held by 'opCtx'.
            MongoDOperationContextSessionWithoutRefresh ocs(newOpCtx.get());
            auto txnParticipant = TransactionParticipant::get(newOpCtx.get());
            LOGV2_DEBUG(21979,
                        3,
                        "Restoring locks of prepared transaction. SessionId: {sessionId} "
                        "TxnNumberAndRetryCounter: {txnNumberAndRetryCounter}",
                        "Restoring locks of prepared transaction",
                        "sessionId"_attr = sessionInfo.getSessionId()->getId(),
                        "txnNumberAndRetryCounter"_attr =
                            txnParticipant.getActiveTxnNumberAndRetryCounter());
            txnParticipant.refreshLocksForPreparedTransaction(newOpCtx.get(), false);
        }
    }

    abortInProgressTransactions(opCtx);

    createTransactionTable(opCtx);
    if (repl::feature_flags::gFeatureFlagRetryableFindAndModify.isEnabledAndIgnoreFCV()) {
        createRetryableFindAndModifyTable(opCtx);
    }
}

boost::optional<UUID> MongoDSessionCatalog::getTransactionTableUUID(OperationContext* opCtx) {
    AutoGetCollection coll(opCtx, NamespaceString::kSessionTransactionsTableNamespace, MODE_IS);

    if (!coll) {
        return boost::none;
    }

    return coll->uuid();
}

void MongoDSessionCatalog::observeDirectWriteToConfigTransactions(OperationContext* opCtx,
                                                                  BSONObj singleSessionDoc) {
    disallowDirectWritesUnderSession(opCtx);

    class KillSessionTokenOnCommit : public RecoveryUnit::Change {
    public:
        KillSessionTokenOnCommit(OperationContext* opCtx,
                                 SessionCatalog::KillToken sessionKillToken)
            : _opCtx(opCtx), _sessionKillToken(std::move(sessionKillToken)) {}

        void commit(boost::optional<Timestamp>) override {
            rollback();
        }

        void rollback() override {
            std::vector<SessionCatalog::KillToken> sessionKillTokenVec;
            sessionKillTokenVec.emplace_back(std::move(_sessionKillToken));
            killSessionTokens(_opCtx, std::move(sessionKillTokenVec));
        }

    private:
        OperationContext* _opCtx;
        SessionCatalog::KillToken _sessionKillToken;
    };

    const auto catalog = SessionCatalog::get(opCtx);

    const auto lsid =
        LogicalSessionId::parse(IDLParserErrorContext("lsid"), singleSessionDoc["_id"].Obj());
    catalog->scanSession(lsid, [&](const ObservableSession& session) {
        const auto participant = TransactionParticipant::get(session);
        uassert(ErrorCodes::PreparedTransactionInProgress,
                str::stream() << "Cannot modify the entry for session "
                              << session.getSessionId().getId()
                              << " because it is in the prepared state",
                !participant.transactionIsPrepared());

        opCtx->recoveryUnit()->registerChange(
            std::make_unique<KillSessionTokenOnCommit>(opCtx, session.kill()));
    });
}

void MongoDSessionCatalog::invalidateAllSessions(OperationContext* opCtx) {
    disallowDirectWritesUnderSession(opCtx);

    const auto catalog = SessionCatalog::get(opCtx);

    std::vector<SessionCatalog::KillToken> sessionKillTokens;

    SessionKiller::Matcher matcher(
        KillAllSessionsByPatternSet{makeKillAllSessionsByPattern(opCtx)});
    catalog->scanSessions(matcher, [&sessionKillTokens](const ObservableSession& session) {
        sessionKillTokens.emplace_back(session.kill());
    });

    killSessionTokens(opCtx, std::move(sessionKillTokens));
}

int MongoDSessionCatalog::reapSessionsOlderThan(OperationContext* opCtx,
                                                SessionsCollection& sessionsCollection,
                                                Date_t possiblyExpired) {
    const auto expiredTransactionSessionIdsStillInUse =
        removeExpiredTransactionSessionsNotInUseFromMemory(
            opCtx, sessionsCollection, possiblyExpired);

    // The "unsafe" check for primary below is a best-effort attempt to ensure that the on-disk
    // state reaping code doesn't run if the node is secondary and cause log spam. It is a work
    // around the fact that the logical sessions cache is not registered to listen for replication
    // state changes.
    const auto replCoord = repl::ReplicationCoordinator::get(opCtx);
    if (!replCoord->canAcceptWritesForDatabase_UNSAFE(opCtx, NamespaceString::kConfigDb))
        return 0;

    return removeExpiredTransactionSessionsFromDisk(
        opCtx, sessionsCollection, possiblyExpired, expiredTransactionSessionIdsStillInUse);
}

int MongoDSessionCatalog::removeSessionsTransactionRecords(
    OperationContext* opCtx, const std::vector<LogicalSessionId>& transactionSessionIdsToRemove) {
    std::vector<LogicalSessionId> nextLsidBatch;
    int numReaped = 0;
    for (const auto& transactionSessionIdToRemove : transactionSessionIdsToRemove) {
        nextLsidBatch.push_back(transactionSessionIdToRemove);
        if (nextLsidBatch.size() > MongoDSessionCatalog::kMaxSessionDeletionBatchSize) {
            numReaped += removeSessionsTransactionRecordsFromDisk(opCtx, nextLsidBatch);
            nextLsidBatch.clear();
        }
    }
    numReaped += removeSessionsTransactionRecordsFromDisk(opCtx, nextLsidBatch);

    return numReaped;
}

MongoDOperationContextSession::MongoDOperationContextSession(OperationContext* opCtx)
    : _operationContextSession(opCtx) {
    invariant(!opCtx->getClient()->isInDirectClient());

    auto txnParticipant = TransactionParticipant::get(opCtx);
    txnParticipant.refreshFromStorageIfNeeded(opCtx);
}

MongoDOperationContextSession::~MongoDOperationContextSession() = default;

void MongoDOperationContextSession::checkIn(OperationContext* opCtx,
                                            OperationContextSession::CheckInReason reason) {
    OperationContextSession::checkIn(opCtx, reason);
}

void MongoDOperationContextSession::checkOut(OperationContext* opCtx) {
    OperationContextSession::checkOut(opCtx);
    auto txnParticipant = TransactionParticipant::get(opCtx);
    txnParticipant.refreshFromStorageIfNeeded(opCtx);
}

MongoDOperationContextSessionWithoutRefresh::MongoDOperationContextSessionWithoutRefresh(
    OperationContext* opCtx)
    : _operationContextSession(opCtx), _opCtx(opCtx) {
    invariant(!opCtx->getClient()->isInDirectClient());
    const auto clientTxnNumber = *opCtx->getTxnNumber();
    const auto clientTxnRetryCounter = *opCtx->getTxnRetryCounter();

    auto txnParticipant = TransactionParticipant::get(opCtx);
    txnParticipant.beginOrContinueTransactionUnconditionally(
        opCtx, {clientTxnNumber, clientTxnRetryCounter});
}

MongoDOperationContextSessionWithoutRefresh::~MongoDOperationContextSessionWithoutRefresh() {
    const auto txnParticipant = TransactionParticipant::get(_opCtx);
    // A session on secondaries should never be checked back in with a TransactionParticipant that
    // isn't prepared, aborted, or committed.
    invariant(!txnParticipant.transactionIsInProgress());
}

MongoDOperationContextSessionWithoutOplogRead::MongoDOperationContextSessionWithoutOplogRead(
    OperationContext* opCtx)
    : _operationContextSession(opCtx), _opCtx(opCtx) {
    invariant(!opCtx->getClient()->isInDirectClient());

    auto txnParticipant = TransactionParticipant::get(opCtx);
    txnParticipant.refreshFromStorageIfNeededNoOplogEntryFetch(opCtx);
}

MongoDOperationContextSessionWithoutOplogRead::~MongoDOperationContextSessionWithoutOplogRead() =
    default;

}  // namespace mongo