path: root/src/mongo/db/catalog/validate_state.cpp

/**
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#include "mongo/platform/basic.h"

#include "mongo/db/catalog/validate_state.h"

#include "mongo/db/catalog/collection.h"
#include "mongo/db/catalog/collection_catalog.h"
#include "mongo/db/catalog/database_holder.h"
#include "mongo/db/catalog/index_consistency.h"
#include "mongo/db/catalog/validate_adaptor.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/index/index_access_method.h"
#include "mongo/db/operation_context.h"
#include "mongo/logv2/log.h"
#include "mongo/util/fail_point.h"

#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kStorage


namespace mongo {

MONGO_FAIL_POINT_DEFINE(hangDuringYieldingLocksForValidation);

namespace CollectionValidation {

ValidateState::ValidateState(OperationContext* opCtx,
                             const NamespaceString& nss,
                             ValidateMode mode,
                             RepairMode repairMode,
                             bool turnOnExtraLoggingForTest)
    : _nss(nss),
      _mode(mode),
      _repairMode(repairMode),
      _dataThrottle(opCtx),
      _extraLoggingForTest(turnOnExtraLoggingForTest) {

    // Subsequent re-locks will use the UUID when 'background' is true.
    if (isBackground()) {
        // Avoid taking the PBWM lock, which will stall replication if this is a secondary node
        // being validated.
        _noPBWM.emplace(opCtx->lockState());

        _globalLock.emplace(opCtx, MODE_IS);
        _databaseLock.emplace(opCtx, _nss.db(), MODE_IS);
        _collectionLock.emplace(opCtx, _nss, MODE_IS);
    } else {
        _databaseLock.emplace(opCtx, _nss.db(), MODE_IX);
        _collectionLock.emplace(opCtx, _nss, MODE_X);
    }

    _database = _databaseLock->getDb() ? _databaseLock->getDb() : nullptr;
    if (_database)
        _collection = CollectionCatalog::get(opCtx)->lookupCollectionByNamespace(opCtx, _nss);

    if (!_collection) {
        if (CollectionCatalog::get(opCtx)->lookupView(opCtx, _nss)) {
            uasserted(ErrorCodes::CommandNotSupportedOnView, "Cannot validate a view");
        }

        uasserted(ErrorCodes::NamespaceNotFound,
                  str::stream() << "Collection '" << _nss << "' does not exist to validate.");
    }

    // RepairMode is incompatible with the ValidateModes kBackground and
    // kForegroundFullEnforceFastCount.
    if (fixErrors()) {
        invariant(!isBackground());
        invariant(!shouldEnforceFastCount());
    }

    if (adjustMultikey()) {
        invariant(!isBackground());
    }

    _uuid = _collection->uuid();
    _catalogGeneration = opCtx->getServiceContext()->getCatalogGeneration();
}

bool ValidateState::shouldEnforceFastCount() const {
    if (_mode == ValidateMode::kForegroundFullEnforceFastCount) {
        if (_nss.isOplog()) {
            // Oplog writers only take a global IX lock, so the oplog can still be written to even
            // during full validation despite its collection X lock. This can cause validate to
            // incorrectly report an incorrect fast count on the oplog when run in enforceFastCount
            // mode.
            return false;
        } else if (_nss == NamespaceString::kIndexBuildEntryNamespace) {
            // Do not enforce fast count on the 'config.system.indexBuilds' collection. This is an
            // internal collection that should not be queried and is empty most of the time.
            return false;
        } else if (_nss == NamespaceString::kSessionTransactionsTableNamespace) {
            // The 'config.transactions' collection is an implicitly replicated collection used for
            // internal bookkeeping for retryable writes and multi-statement transactions.
            // Replication rollback won't adjust the size storer counts for the
            // 'config.transactions' collection. We therefore do not enforce fast count on it.
            return false;
        } else if (_nss == NamespaceString::kConfigImagesNamespace) {
            // The 'config.image_collection' collection is an implicitly replicated collection used
            // for internal bookkeeping for retryable writes. Replication rollback won't adjust the
            // size storer counts for the 'config.image_collection' collection. We therefore do not
            // enforce fast count on it.
            return false;
        }

        return true;
    }

    return false;
}

void ValidateState::yield(OperationContext* opCtx) {
    if (isBackground()) {
        _yieldLocks(opCtx);
    }
    _yieldCursors(opCtx);
}

void ValidateState::_yieldLocks(OperationContext* opCtx) {
    invariant(isBackground());

    // Drop and reacquire the locks.
    _relockDatabaseAndCollection(opCtx);

    uassert(ErrorCodes::Interrupted,
            str::stream() << "Interrupted due to: catalog restart: " << _nss << " (" << *_uuid
                          << ") while validating the collection",
            _catalogGeneration == opCtx->getServiceContext()->getCatalogGeneration());

    // Check if any of the indexes we were validating were dropped. Indexes created while
    // yielding will be ignored.
    for (const auto& index : _indexes) {
        uassert(ErrorCodes::Interrupted,
                str::stream()
                    << "Interrupted due to: index being validated was dropped from collection: "
                    << _nss << " (" << *_uuid << "), index: " << index->descriptor()->indexName(),
                !index->isDropped());
    }
};

void ValidateState::_yieldCursors(OperationContext* opCtx) {
    // Save all the cursors.
    for (const auto& indexCursor : _indexCursors) {
        indexCursor.second->save();
    }

    _traverseRecordStoreCursor->save();
    _seekRecordStoreCursor->save();

    if (isBackground() && _validateTs) {
        // Reset snapshot to help ameliorate WiredTiger cache pressure.
        opCtx->recoveryUnit()->refreshSnapshot();
    }

    // Restore all the cursors.
    for (const auto& indexCursor : _indexCursors) {
        indexCursor.second->restore();
    }

    uassert(ErrorCodes::Interrupted,
            "Interrupted due to: failure to restore yielded traverse cursor",
            _traverseRecordStoreCursor->restore());
    uassert(ErrorCodes::Interrupted,
            "Interrupted due to: failure to restore yielded seek cursor",
            _seekRecordStoreCursor->restore());
}

void ValidateState::initializeCursors(OperationContext* opCtx) {
    invariant(!_traverseRecordStoreCursor && !_seekRecordStoreCursor && _indexCursors.size() == 0 &&
              _indexes.size() == 0);

    // Background validation (on replica sets) will read from a snapshot opened on the kNoOverlap
    // read source, which is the minimum of the last applied and all durable timestamps, instead of
    // the latest data. Using the kNoOverlap read source prevents us from having to take the PBWM
    // lock, which blocks replication. We cannot solely rely on the all durable timestamp as it can
    // be set while we're in the middle of applying a batch on secondary nodes.
    // Background validation on standalones uses the kNoTimestamp read source because standalones
    // have no timestamps to use for maintaining a consistent snapshot.
    RecoveryUnit::ReadSource rs = RecoveryUnit::ReadSource::kNoTimestamp;
    if (isBackground()) {
        opCtx->recoveryUnit()->abandonSnapshot();
        // Background validation is expecting to read from the no overlap timestamp, but
        // standalones do not support timestamps. Therefore, if this process is currently running as
        // a standalone, don't use a timestamp.

        if (repl::ReplicationCoordinator::get(opCtx)->isReplEnabled()) {
            rs = RecoveryUnit::ReadSource::kNoOverlap;
        } else {
            rs = RecoveryUnit::ReadSource::kNoTimestamp;
        }
        opCtx->recoveryUnit()->setTimestampReadSource(rs);
    }

    // We want to share the same data throttle instance across all the cursors used during this
    // validation. Validations started on other collections will not share the same data
    // throttle instance.
    if (!isBackground()) {
        _dataThrottle.turnThrottlingOff();
    }

    _traverseRecordStoreCursor = std::make_unique<SeekableRecordThrottleCursor>(
        opCtx, _collection->getRecordStore(), &_dataThrottle);
    _seekRecordStoreCursor = std::make_unique<SeekableRecordThrottleCursor>(
        opCtx, _collection->getRecordStore(), &_dataThrottle);

    if (rs != RecoveryUnit::ReadSource::kNoTimestamp) {
        invariant(rs == RecoveryUnit::ReadSource::kNoOverlap);
        invariant(isBackground());
        _validateTs = opCtx->recoveryUnit()->getPointInTimeReadTimestamp(opCtx);
    }

    const IndexCatalog* indexCatalog = _collection->getIndexCatalog();
    // The index iterator for ready indexes is timestamp-aware and will only return indexes that
    // are visible at our read time.
    const std::unique_ptr<IndexCatalog::IndexIterator> it =
        indexCatalog->getIndexIterator(opCtx, /*includeUnfinished*/ false);
    while (it->more()) {
        const IndexCatalogEntry* entry = it->next();
        const IndexDescriptor* desc = entry->descriptor();

        auto iam = entry->accessMethod()->asSortedData();
        if (!iam)
            continue;

        _indexCursors.emplace(
            desc->indexName(),
            std::make_unique<SortedDataInterfaceThrottleCursor>(opCtx, iam, &_dataThrottle));

        _indexes.push_back(indexCatalog->getEntryShared(desc));
    }

    // Because SeekableRecordCursors don't have a method to reset to the start, we save and then
    // use a seek to the first RecordId to reset the cursor (and reuse it) as needed. When
    // iterating through a Record Store cursor, we initialize the loop (and obtain the first
    // Record) with a seek to the first Record (using firstRecordId). Subsequent loop iterations
    // use cursor->next() to get subsequent Records. However, if the Record Store is empty,
    // there is no first record. In this case, we set the first Record Id to an invalid RecordId
    // (RecordId()), which will halt iteration at the initialization step.
    const boost::optional<Record> record = _traverseRecordStoreCursor->next(opCtx);
    _firstRecordId = record ? record->id : RecordId();
}

void ValidateState::_relockDatabaseAndCollection(OperationContext* opCtx) {
    invariant(isBackground());

    _collectionLock.reset();
    _databaseLock.reset();

    if (MONGO_unlikely(hangDuringYieldingLocksForValidation.shouldFail())) {
        LOGV2(20411, "Hanging on fail point 'hangDuringYieldingLocksForValidation'");
        hangDuringYieldingLocksForValidation.pauseWhileSet();
    }

    std::string dbErrMsg = str::stream()
        << "Interrupted due to: database drop: " << _nss.db()
        << " while validating collection: " << _nss << " (" << *_uuid << ")";

    _databaseLock.emplace(opCtx, _nss.db(), MODE_IS);
    _database = DatabaseHolder::get(opCtx)->getDb(opCtx, _nss.dbName());
    uassert(ErrorCodes::Interrupted, dbErrMsg, _database);
    uassert(ErrorCodes::Interrupted, dbErrMsg, !_database->isDropPending(opCtx));

    std::string collErrMsg = str::stream() << "Interrupted due to: collection drop: " << _nss
                                           << " (" << *_uuid << ") while validating the collection";

    try {
        NamespaceStringOrUUID nssOrUUID(std::string(_nss.db()), *_uuid);
        _collectionLock.emplace(opCtx, nssOrUUID, MODE_IS);
    } catch (const ExceptionFor<ErrorCodes::NamespaceNotFound>&) {
        uasserted(ErrorCodes::Interrupted, collErrMsg);
    }

    _collection = CollectionCatalog::get(opCtx)->lookupCollectionByUUID(opCtx, *_uuid);
    uassert(ErrorCodes::Interrupted, collErrMsg, _collection);

    // The namespace of the collection can be changed during a same database collection rename.
    _nss = _collection->ns();
}

}  // namespace CollectionValidation
}  // namespace mongo