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

/**
 *    Copyright (C) 2019-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)
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#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kStorage

#include "mongo/platform/basic.h"

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

#include "mongo/db/catalog/collection.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/db/storage/durable_catalog.h"
#include "mongo/db/views/view_catalog.h"
#include "mongo/util/fail_point.h"
#include "mongo/util/log.h"

namespace mongo {

MONGO_FAIL_POINT_DEFINE(hangDuringYieldingLocksForValidation);

namespace CollectionValidation {

ValidateState::ValidateState(OperationContext* opCtx,
                             const NamespaceString& nss,
                             bool background,
                             bool fullValidate)
    : _nss(nss), _background(background), _fullValidate(fullValidate) {

    // Subsequent re-locks will use the UUID when 'background' is true.
    if (_background) {
        _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;
    _collection =
        _database ? CollectionCatalog::get(opCtx).lookupCollectionByNamespace(_nss) : nullptr;

    if (!_collection) {
        if (_database && ViewCatalog::get(_database)->lookup(opCtx, _nss.ns())) {
            uasserted(ErrorCodes::CommandNotSupportedOnView, "Cannot validate a view");
        }

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

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

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

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

    // 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) {
    invariant(!_background);

    // Mobile does not support saving and restoring cursors, so we skip yielding cursors for it.
    if (storageGlobalParams.engine == "mobile") {
        return;
    }

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

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

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

    // Restore cannot fail while holding an exclusive collection lock.
    invariant(_traverseRecordStoreCursor->restore());
    invariant(_seekRecordStoreCursor->restore());
}

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

    // Background validation will read from the last stable checkpoint instead of the latest data.
    // This allows concurrent writes to go ahead without interfering with validation's view of the
    // data. The checkpoint lock must be taken around cursor creation to ensure all cursors point at
    // the same checkpoint, i.e. a consistent view of the collection data.
    std::unique_ptr<StorageEngine::CheckpointLock> checkpointCursorsLock;
    if (_background) {
        invariant(!opCtx->lockState()->isCollectionLockedForMode(_nss, MODE_X));
        auto storageEngine = opCtx->getServiceContext()->getStorageEngine();
        invariant(storageEngine->supportsCheckpoints());
        opCtx->recoveryUnit()->abandonSnapshot();
        opCtx->recoveryUnit()->setTimestampReadSource(RecoveryUnit::ReadSource::kCheckpoint);
        checkpointCursorsLock = storageEngine->getCheckpointLock(opCtx);
    }

    // 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 (!_background) {
        _dataThrottle.turnThrottlingOff();
    }

    try {
        _traverseRecordStoreCursor = std::make_unique<SeekableRecordThrottleCursor>(
            opCtx, _collection->getRecordStore(), &_dataThrottle);
        _seekRecordStoreCursor = std::make_unique<SeekableRecordThrottleCursor>(
            opCtx, _collection->getRecordStore(), &_dataThrottle);
    } catch (const ExceptionFor<ErrorCodes::CursorNotFound>& ex) {
        invariant(_background);
        // End the validation if we can't open a checkpoint cursor on the collection.
        log() << "Skipping background validation on collection '" << _nss
              << "' because the collection is not yet in a checkpoint: " << ex;
        throw;
    }

    std::vector<std::string> readyDurableIndexes;
    try {
        DurableCatalog::get(opCtx)->getReadyIndexes(opCtx, _nss, &readyDurableIndexes);
    } catch (const ExceptionFor<ErrorCodes::CursorNotFound>& ex) {
        invariant(_background);
        log() << "Skipping background validation on collection '" << _nss
              << "' because the data is not yet in a checkpoint: " << ex;
        throw;
    }

    const IndexCatalog* indexCatalog = _collection->getIndexCatalog();
    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();

        // Filter out any in-memory index in the collection that is not in our PIT view of the MDB
        // catalog. This is only important when background:true because we are then reading from the
        // checkpoint's view of the MDB catalog and data.
        bool isIndexDurable =
            std::find(readyDurableIndexes.begin(), readyDurableIndexes.end(), desc->indexName()) !=
            readyDurableIndexes.end();
        if (_background && !isIndexDurable) {
            log() << "Skipping validation on index '" << desc->indexName() << "' in collection '"
                  << _nss << "' because the index is not yet in a checkpoint.";
            continue;
        }

        // Read the index's ident from disk (the checkpoint if background:true). If it does not
        // match the in-memory ident saved in the IndexCatalogEntry, then our PIT view of the index
        // is old and the index has been dropped and recreated. In this case we will skip it since
        // there is no utility in checking a dropped index (we also cannot currently access it
        // because its in-memory representation is gone).
        auto diskIndexIdent =
            opCtx->getServiceContext()->getStorageEngine()->getCatalog()->getIndexIdent(
                opCtx, _nss, desc->indexName());
        if (entry->getIdent() != diskIndexIdent) {
            log() << "Skipping validation on index '" << desc->indexName() << "' in collection '"
                  << _nss << "' because the index was recreated and is not yet in a checkpoint.";
            continue;
        }

        try {
            _indexCursors.emplace(desc->indexName(),
                                  std::make_unique<SortedDataInterfaceThrottleCursor>(
                                      opCtx, entry->accessMethod(), &_dataThrottle));
        } catch (const ExceptionFor<ErrorCodes::CursorNotFound>& ex) {
            invariant(_background);
            // This can only happen if the checkpoint has the MDB catalog entry for the index, but
            // not the corresponding index table.
            log() << "Skipping validation on index '" << desc->indexName() << "' in collection '"
                  << _nss << "' because the index data is not in a checkpoint: " << ex;
            continue;
        }

        // Skip any newly created indexes that, because they were built with a WT bulk loader, are
        // checkpoint'ed but not yet consistent with the rest of checkpoint's PIT view of the data.
        if (_background &&
            opCtx->getServiceContext()->getStorageEngine()->isInIndividuallyCheckpointedIndexesList(
                diskIndexIdent)) {
            _indexCursors.erase(desc->indexName());
            log() << "Skipping validation on index '" << desc->indexName() << "' in collection '"
                  << _nss << "' because the index data is not yet consistent in the checkpoint.";
            continue;
        }

        _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(_background);

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

    if (MONGO_unlikely(hangDuringYieldingLocksForValidation.shouldFail())) {
        log() << "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.db());
    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(*_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