/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.cassandra.db.commitlog;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.concurrent.*;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.util.concurrent.RateLimiter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.commitlog.CommitLogSegment.CDCState;
import org.apache.cassandra.exceptions.WriteTimeoutException;
import org.apache.cassandra.io.util.FileUtils;
import org.apache.cassandra.utils.DirectorySizeCalculator;
import org.apache.cassandra.utils.NoSpamLogger;

public class CommitLogSegmentManagerCDC extends AbstractCommitLogSegmentManager
{
    static final Logger logger = LoggerFactory.getLogger(CommitLogSegmentManagerCDC.class);
    private final CDCSizeTracker cdcSizeTracker;

    public CommitLogSegmentManagerCDC(final CommitLog commitLog, String storageDirectory)
    {
        super(commitLog, storageDirectory);
        cdcSizeTracker = new CDCSizeTracker(this, new File(DatabaseDescriptor.getCDCLogLocation()));
    }

    @Override
    void start()
    {
        cdcSizeTracker.start();
        super.start();
    }

    public void discard(CommitLogSegment segment, boolean delete)
    {
        segment.close();
        addSize(-segment.onDiskSize());

        cdcSizeTracker.processDiscardedSegment(segment);

        if (segment.getCDCState() == CDCState.CONTAINS)
            FileUtils.renameWithConfirm(segment.logFile.getAbsolutePath(), DatabaseDescriptor.getCDCLogLocation() + File.separator + segment.logFile.getName());
        else
        {
            if (delete)
                FileUtils.deleteWithConfirm(segment.logFile);
        }
    }

    
Initiates the shutdown process for the management thread. Also stops the cdc on-disk size calculator executor.
/**
     * Initiates the shutdown process for the management thread. Also stops the cdc on-disk size calculator executor.
     */
    public void shutdown()
    {
        cdcSizeTracker.shutdown();
        super.shutdown();
    }

    
Reserve space in the current segment for the provided mutation or, if there isn't space available,
create a new segment. For CDC mutations, allocation is expected to throw WTE if the segment disallows CDC mutations.
Params:
mutation – Mutation to allocate in segment manager
size – total size (overhead + serialized) of mutation
Throws:
WriteTimeoutException – If segment disallows CDC mutations, we throw WTE
Returns:
the created Allocation object/**
     * Reserve space in the current segment for the provided mutation or, if there isn't space available,
     * create a new segment. For CDC mutations, allocation is expected to throw WTE if the segment disallows CDC mutations.
     *
     * @param mutation Mutation to allocate in segment manager
     * @param size total size (overhead + serialized) of mutation
     * @return the created Allocation object
     * @throws WriteTimeoutException If segment disallows CDC mutations, we throw WTE
     */
    @Override
    public CommitLogSegment.Allocation allocate(Mutation mutation, int size) throws WriteTimeoutException
    {
        CommitLogSegment segment = allocatingFrom();
        CommitLogSegment.Allocation alloc;

        throwIfForbidden(mutation, segment);
        while ( null == (alloc = segment.allocate(mutation, size)) )
        {
            // Failed to allocate, so move to a new segment with enough room if possible.
            advanceAllocatingFrom(segment);
            segment = allocatingFrom();

            throwIfForbidden(mutation, segment);
        }

        if (mutation.trackedByCDC())
            segment.setCDCState(CDCState.CONTAINS);

        return alloc;
    }

    private void throwIfForbidden(Mutation mutation, CommitLogSegment segment) throws WriteTimeoutException
    {
        if (mutation.trackedByCDC() && segment.getCDCState() == CDCState.FORBIDDEN)
        {
            cdcSizeTracker.submitOverflowSizeRecalculation();
            NoSpamLogger.log(logger,
                             NoSpamLogger.Level.WARN,
                             10,
                             TimeUnit.SECONDS,
                             "Rejecting Mutation containing CDC-enabled table. Free up space in {}.",
                             DatabaseDescriptor.getCDCLogLocation());
            throw new WriteTimeoutException(WriteType.CDC, ConsistencyLevel.LOCAL_ONE, 0, 1);
        }
    }

    
Move files to cdc_raw after replay, since recovery will flush to SSTable and these mutations won't be available
in the CL subsystem otherwise.
/**
     * Move files to cdc_raw after replay, since recovery will flush to SSTable and these mutations won't be available
     * in the CL subsystem otherwise.
     */
    void handleReplayedSegment(final File file)
    {
        logger.trace("Moving (Unopened) segment {} to cdc_raw directory after replay", file);
        FileUtils.renameWithConfirm(file.getAbsolutePath(), DatabaseDescriptor.getCDCLogLocation() + File.separator + file.getName());
        cdcSizeTracker.addFlushedSize(file.length());
    }

    
On segment creation, flag whether the segment should accept CDC mutations or not based on the total currently
allocated unflushed CDC segments and the contents of cdc_raw
/**
     * On segment creation, flag whether the segment should accept CDC mutations or not based on the total currently
     * allocated unflushed CDC segments and the contents of cdc_raw
     */
    public CommitLogSegment createSegment()
    {
        CommitLogSegment segment = CommitLogSegment.createSegment(commitLog, this);
        cdcSizeTracker.processNewSegment(segment);
        return segment;
    }

    
Tracks total disk usage of CDC subsystem, defined by the summation of all unflushed CommitLogSegments with CDC
data in them and all segments archived into cdc_raw.
Allows atomic increment/decrement of unflushed size, however only allows increment on flushed and requires a full
directory walk to determine any potential deletions by CDC consumer.
/**
     * Tracks total disk usage of CDC subsystem, defined by the summation of all unflushed CommitLogSegments with CDC
     * data in them and all segments archived into cdc_raw.
     *
     * Allows atomic increment/decrement of unflushed size, however only allows increment on flushed and requires a full
     * directory walk to determine any potential deletions by CDC consumer.
     */
    private static class CDCSizeTracker extends DirectorySizeCalculator
    {
        private final RateLimiter rateLimiter = RateLimiter.create(1000.0 / DatabaseDescriptor.getCDCDiskCheckInterval());
        private ExecutorService cdcSizeCalculationExecutor;
        private CommitLogSegmentManagerCDC segmentManager;
        private volatile long unflushedCDCSize;

        // Used instead of size during walk to remove chance of over-allocation
        private volatile long sizeInProgress = 0;

        CDCSizeTracker(CommitLogSegmentManagerCDC segmentManager, File path)
        {
            super(path);
            this.segmentManager = segmentManager;
        }

        
Needed for stop/restart during unit tests
/**
         * Needed for stop/restart during unit tests
         */
        public void start()
        {
            size = 0;
            unflushedCDCSize = 0;
            cdcSizeCalculationExecutor = new ThreadPoolExecutor(1, 1, 1000, TimeUnit.SECONDS, new SynchronousQueue<>(), new ThreadPoolExecutor.DiscardPolicy());
        }

        
Synchronous size recalculation on each segment creation/deletion call could lead to very long delays in new
segment allocation, thus long delays in thread signaling to wake waiting allocation / writer threads.
This can be reached either from the segment management thread in ABstractCommitLogSegmentManager or from the
size recalculation executor, so we synchronize on this object to reduce the race overlap window available for
size to get off.
Reference DirectorySizerBench for more information about performance of the directory size recalc.
/**
         * Synchronous size recalculation on each segment creation/deletion call could lead to very long delays in new
         * segment allocation, thus long delays in thread signaling to wake waiting allocation / writer threads.
         *
         * This can be reached either from the segment management thread in ABstractCommitLogSegmentManager or from the
         * size recalculation executor, so we synchronize on this object to reduce the race overlap window available for
         * size to get off.
         *
         * Reference DirectorySizerBench for more information about performance of the directory size recalc.
         */
        void processNewSegment(CommitLogSegment segment)
        {
            // See synchronization in CommitLogSegment.setCDCState
            synchronized(segment.cdcStateLock)
            {
                segment.setCDCState(defaultSegmentSize() + totalCDCSizeOnDisk() > allowableCDCBytes()
                                    ? CDCState.FORBIDDEN
                                    : CDCState.PERMITTED);
                if (segment.getCDCState() == CDCState.PERMITTED)
                    unflushedCDCSize += defaultSegmentSize();
            }

            // Take this opportunity to kick off a recalc to pick up any consumer file deletion.
            submitOverflowSizeRecalculation();
        }

        void processDiscardedSegment(CommitLogSegment segment)
        {
            // See synchronization in CommitLogSegment.setCDCState
            synchronized(segment.cdcStateLock)
            {
                // Add to flushed size before decrementing unflushed so we don't have a window of false generosity
                if (segment.getCDCState() == CDCState.CONTAINS)
                    size += segment.onDiskSize();
                if (segment.getCDCState() != CDCState.FORBIDDEN)
                    unflushedCDCSize -= defaultSegmentSize();
            }

            // Take this opportunity to kick off a recalc to pick up any consumer file deletion.
            submitOverflowSizeRecalculation();
        }

        private long allowableCDCBytes()
        {
            return (long)DatabaseDescriptor.getCDCSpaceInMB() * 1024 * 1024;
        }

        public void submitOverflowSizeRecalculation()
        {
            try
            {
                cdcSizeCalculationExecutor.submit(() -> recalculateOverflowSize());
            }
            catch (RejectedExecutionException e)
            {
                // Do nothing. Means we have one in flight so this req. should be satisfied when it completes.
            }
        }

        private void recalculateOverflowSize()
        {
            rateLimiter.acquire();
            calculateSize();
            CommitLogSegment allocatingFrom = segmentManager.allocatingFrom();
            if (allocatingFrom.getCDCState() == CDCState.FORBIDDEN)
                processNewSegment(allocatingFrom);
        }

        private int defaultSegmentSize()
        {
            return DatabaseDescriptor.getCommitLogSegmentSize();
        }

        private void calculateSize()
        {
            try
            {
                // The Arrays.stream approach is considerably slower on Windows than linux
                sizeInProgress = 0;
                Files.walkFileTree(path.toPath(), this);
                size = sizeInProgress;
            }
            catch (IOException ie)
            {
                CommitLog.instance.handleCommitError("Failed CDC Size Calculation", ie);
            }
        }

        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException
        {
            sizeInProgress += attrs.size();
            return FileVisitResult.CONTINUE;
        }

        private void addFlushedSize(long toAdd)
        {
            size += toAdd;
        }

        private long totalCDCSizeOnDisk()
        {
            return unflushedCDCSize + size;
        }

        public void shutdown()
        {
            cdcSizeCalculationExecutor.shutdown();
        }
    }

    
Only use for testing / validation that size tracker is working. Not for production use.
/**
     * Only use for testing / validation that size tracker is working. Not for production use.
     */
    @VisibleForTesting
    public long updateCDCTotalSize()
    {
        cdcSizeTracker.submitOverflowSizeRecalculation();

        // Give the update time to run
        try
        {
            Thread.sleep(DatabaseDescriptor.getCDCDiskCheckInterval() + 10);
        }
        catch (InterruptedException e) {}

        return cdcSizeTracker.totalCDCSizeOnDisk();
    }
}