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Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.
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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.kernel.recovery;

import java.io.IOException;

import org.neo4j.io.pagecache.context.CursorContext;
import org.neo4j.io.pagecache.tracing.PageCacheTracer;
import org.neo4j.kernel.impl.transaction.log.LogPosition;
import org.neo4j.kernel.impl.transaction.log.LogicalTransactionStore;
import org.neo4j.kernel.impl.transaction.log.TransactionCursor;
import org.neo4j.kernel.impl.transaction.log.entry.LogEntryCommit;
import org.neo4j.kernel.impl.transaction.log.files.LogFiles;
import org.neo4j.logging.Log;
import org.neo4j.storageengine.api.LogVersionRepository;
import org.neo4j.storageengine.api.StorageEngine;
import org.neo4j.storageengine.api.TransactionApplicationMode;
import org.neo4j.storageengine.api.TransactionIdStore;

import static org.neo4j.kernel.impl.transaction.log.entry.LogVersions.CURRENT_FORMAT_LOG_HEADER_SIZE;
import static org.neo4j.storageengine.api.LogVersionRepository.INITIAL_LOG_VERSION;

public class DefaultRecoveryService implements RecoveryService
{
    private final RecoveryStartInformationProvider recoveryStartInformationProvider;
    private final StorageEngine storageEngine;
    private final TransactionIdStore transactionIdStore;
    private final LogicalTransactionStore logicalTransactionStore;
    private final LogVersionRepository logVersionRepository;
    private final Log log;
    private final boolean doParallelRecovery;

    DefaultRecoveryService( StorageEngine storageEngine, TransactionIdStore transactionIdStore,
            LogicalTransactionStore logicalTransactionStore, LogVersionRepository logVersionRepository, LogFiles logFiles,
            RecoveryStartInformationProvider.Monitor monitor, Log log, boolean doParallelRecovery )
    {
        this.storageEngine = storageEngine;
        this.transactionIdStore = transactionIdStore;
        this.logicalTransactionStore = logicalTransactionStore;
        this.logVersionRepository = logVersionRepository;
        this.log = log;
        this.doParallelRecovery = doParallelRecovery;
        this.recoveryStartInformationProvider = new RecoveryStartInformationProvider( logFiles, monitor );
    }

    @Override
    public RecoveryStartInformation getRecoveryStartInformation()
    {
        return recoveryStartInformationProvider.get();
    }

    @Override
    public RecoveryApplier getRecoveryApplier( TransactionApplicationMode mode, PageCacheTracer cacheTracer, String tracerTag )
    {
        if ( doParallelRecovery )
        {
            return new ParallelRecoveryVisitor( storageEngine, mode, cacheTracer, tracerTag );
        }
        return new RecoveryVisitor( storageEngine, mode, cacheTracer, tracerTag );
    }

    @Override
    public TransactionCursor getTransactions( long transactionId ) throws IOException
    {
        return logicalTransactionStore.getTransactions( transactionId );
    }

    @Override
    public TransactionCursor getTransactions( LogPosition position ) throws IOException
    {
        return logicalTransactionStore.getTransactions( position );
    }

    @Override
    public TransactionCursor getTransactionsInReverseOrder( LogPosition position ) throws IOException
    {
        return logicalTransactionStore.getTransactionsInReverseOrder( position );
    }

    @Override
    public void transactionsRecovered( LogEntryCommit lastRecoveredTransaction, LogPosition lastRecoveredTransactionPosition,
            LogPosition positionAfterLastRecoveredTransaction, LogPosition checkpointPosition, boolean missingLogs, CursorContext cursorContext )
    {
        if ( missingLogs )
        {
            // in case if logs are missing we need to reset position of last committed transaction since
            // this information influencing checkpoint that will be created and if we will not gonna do that
            // it will still reference old offset from logs that are gone and as result log position in checkpoint record will be incorrect
            // and that can cause partial next recovery.
            var lastClosedTransactionData = transactionIdStore.getLastClosedTransaction();
            long logVersion = lastClosedTransactionData.getLogPosition().getLogVersion();
            log.warn( "Recovery detected that transaction logs were missing. " +
                    "Resetting offset of last closed transaction to point to the head of %d transaction log file.", logVersion );
            transactionIdStore.resetLastClosedTransaction( lastClosedTransactionData.getTransactionId(), logVersion, CURRENT_FORMAT_LOG_HEADER_SIZE, true,
                    cursorContext );
            logVersionRepository.setCurrentLogVersion( logVersion, cursorContext );
            long checkpointLogVersion = logVersionRepository.getCheckpointLogVersion();
            if ( checkpointLogVersion < 0 )
            {
                log.warn( "Recovery detected that checkpoint log version is invalid. " +
                        "Resetting version to start from the beginning. Current recorded version: %d. New version: 0.", checkpointLogVersion );
                logVersionRepository.setCheckpointLogVersion( INITIAL_LOG_VERSION, cursorContext );
            }
            return;
        }
        if ( lastRecoveredTransaction != null )
        {
            transactionIdStore.setLastCommittedAndClosedTransactionId( lastRecoveredTransaction.getTxId(), lastRecoveredTransaction.getChecksum(),
                    lastRecoveredTransaction.getTimeWritten(), lastRecoveredTransactionPosition.getByteOffset(),
                    lastRecoveredTransactionPosition.getLogVersion(), cursorContext );
        }
        else
        {
            // we do not have last recovered transaction but recovery was still triggered
            // this happens when we read past end of the log file or can't read it at all but recovery was enforced
            // which means that log files after last recovered position can't be trusted and we need to reset last closed tx log info
            long lastClosedTransactionId = transactionIdStore.getLastClosedTransactionId();
            log.warn( "Recovery detected that transaction logs tail can't be trusted. " +
                    "Resetting offset of last closed transaction to point to the last recoverable log position: " + positionAfterLastRecoveredTransaction );
            transactionIdStore.resetLastClosedTransaction( lastClosedTransactionId, positionAfterLastRecoveredTransaction.getLogVersion(),
                    positionAfterLastRecoveredTransaction.getByteOffset(), false, cursorContext );
        }

        logVersionRepository.setCurrentLogVersion( positionAfterLastRecoveredTransaction.getLogVersion(), cursorContext );
        logVersionRepository.setCheckpointLogVersion( checkpointPosition.getLogVersion(), cursorContext );
    }
}