kafka FileLogInputStream 源码

kafka FileLogInputStream 代码

文件路径：/clients/src/main/java/org/apache/kafka/common/record/FileLogInputStream.java

/*
 * 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.kafka.common.record;

import org.apache.kafka.common.KafkaException;
import org.apache.kafka.common.errors.CorruptRecordException;
import org.apache.kafka.common.record.AbstractLegacyRecordBatch.LegacyFileChannelRecordBatch;
import org.apache.kafka.common.record.DefaultRecordBatch.DefaultFileChannelRecordBatch;
import org.apache.kafka.common.utils.BufferSupplier;
import org.apache.kafka.common.utils.CloseableIterator;
import org.apache.kafka.common.utils.Utils;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Iterator;
import java.util.Objects;

import static org.apache.kafka.common.record.Records.LOG_OVERHEAD;
import static org.apache.kafka.common.record.Records.HEADER_SIZE_UP_TO_MAGIC;
import static org.apache.kafka.common.record.Records.MAGIC_OFFSET;
import static org.apache.kafka.common.record.Records.OFFSET_OFFSET;
import static org.apache.kafka.common.record.Records.SIZE_OFFSET;

/**
 * A log input stream which is backed by a {@link FileChannel}.
 */
public class FileLogInputStream implements LogInputStream<FileLogInputStream.FileChannelRecordBatch> {
    private int position;
    private final int end;
    private final FileRecords fileRecords;
    private final ByteBuffer logHeaderBuffer = ByteBuffer.allocate(HEADER_SIZE_UP_TO_MAGIC);

    /**
     * Create a new log input stream over the FileChannel
     * @param records Underlying FileRecords instance
     * @param start Position in the file channel to start from
     * @param end Position in the file channel not to read past
     */
    FileLogInputStream(FileRecords records,
                       int start,
                       int end) {
        this.fileRecords = records;
        this.position = start;
        this.end = end;
    }

    @Override
    public FileChannelRecordBatch nextBatch() throws IOException {
        FileChannel channel = fileRecords.channel();
        if (position >= end - HEADER_SIZE_UP_TO_MAGIC)
            return null;

        logHeaderBuffer.rewind();
        Utils.readFullyOrFail(channel, logHeaderBuffer, position, "log header");

        logHeaderBuffer.rewind();
        long offset = logHeaderBuffer.getLong(OFFSET_OFFSET);
        int size = logHeaderBuffer.getInt(SIZE_OFFSET);

        // V0 has the smallest overhead, stricter checking is done later
        if (size < LegacyRecord.RECORD_OVERHEAD_V0)
            throw new CorruptRecordException(String.format("Found record size %d smaller than minimum record " +
                            "overhead (%d) in file %s.", size, LegacyRecord.RECORD_OVERHEAD_V0, fileRecords.file()));

        if (position > end - LOG_OVERHEAD - size)
            return null;

        byte magic = logHeaderBuffer.get(MAGIC_OFFSET);
        final FileChannelRecordBatch batch;

        if (magic < RecordBatch.MAGIC_VALUE_V2)
            batch = new LegacyFileChannelRecordBatch(offset, magic, fileRecords, position, size);
        else
            batch = new DefaultFileChannelRecordBatch(offset, magic, fileRecords, position, size);

        position += batch.sizeInBytes();
        return batch;
    }

    /**
     * Log entry backed by an underlying FileChannel. This allows iteration over the record batches
     * without needing to read the record data into memory until it is needed. The downside
     * is that entries will generally no longer be readable when the underlying channel is closed.
     */
    public abstract static class FileChannelRecordBatch extends AbstractRecordBatch {
        protected final long offset;
        protected final byte magic;
        protected final FileRecords fileRecords;
        protected final int position;
        protected final int batchSize;

        private RecordBatch fullBatch;
        private RecordBatch batchHeader;

        FileChannelRecordBatch(long offset,
                               byte magic,
                               FileRecords fileRecords,
                               int position,
                               int batchSize) {
            this.offset = offset;
            this.magic = magic;
            this.fileRecords = fileRecords;
            this.position = position;
            this.batchSize = batchSize;
        }

        @Override
        public CompressionType compressionType() {
            return loadBatchHeader().compressionType();
        }

        @Override
        public TimestampType timestampType() {
            return loadBatchHeader().timestampType();
        }

        @Override
        public long checksum() {
            return loadBatchHeader().checksum();
        }

        @Override
        public long maxTimestamp() {
            return loadBatchHeader().maxTimestamp();
        }

        public int position() {
            return position;
        }

        @Override
        public byte magic() {
            return magic;
        }

        @Override
        public Iterator<Record> iterator() {
            return loadFullBatch().iterator();
        }

        @Override
        public CloseableIterator<Record> streamingIterator(BufferSupplier bufferSupplier) {
            return loadFullBatch().streamingIterator(bufferSupplier);
        }

        @Override
        public boolean isValid() {
            return loadFullBatch().isValid();
        }

        @Override
        public void ensureValid() {
            loadFullBatch().ensureValid();
        }

        @Override
        public int sizeInBytes() {
            return LOG_OVERHEAD + batchSize;
        }

        @Override
        public void writeTo(ByteBuffer buffer) {
            FileChannel channel = fileRecords.channel();
            try {
                int limit = buffer.limit();
                buffer.limit(buffer.position() + sizeInBytes());
                Utils.readFully(channel, buffer, position);
                buffer.limit(limit);
            } catch (IOException e) {
                throw new KafkaException("Failed to read record batch at position " + position + " from " + fileRecords, e);
            }
        }

        protected abstract RecordBatch toMemoryRecordBatch(ByteBuffer buffer);

        protected abstract int headerSize();

        protected RecordBatch loadFullBatch() {
            if (fullBatch == null) {
                batchHeader = null;
                fullBatch = loadBatchWithSize(sizeInBytes(), "full record batch");
            }
            return fullBatch;
        }

        protected RecordBatch loadBatchHeader() {
            if (fullBatch != null)
                return fullBatch;

            if (batchHeader == null)
                batchHeader = loadBatchWithSize(headerSize(), "record batch header");

            return batchHeader;
        }

        private RecordBatch loadBatchWithSize(int size, String description) {
            FileChannel channel = fileRecords.channel();
            try {
                ByteBuffer buffer = ByteBuffer.allocate(size);
                Utils.readFullyOrFail(channel, buffer, position, description);
                buffer.rewind();
                return toMemoryRecordBatch(buffer);
            } catch (IOException e) {
                throw new KafkaException("Failed to load record batch at position " + position + " from " + fileRecords, e);
            }
        }

        @Override
        public boolean equals(Object o) {
            if (this == o)
                return true;
            if (o == null || getClass() != o.getClass())
                return false;

            FileChannelRecordBatch that = (FileChannelRecordBatch) o;

            FileChannel channel = fileRecords == null ? null : fileRecords.channel();
            FileChannel thatChannel = that.fileRecords == null ? null : that.fileRecords.channel();

            return offset == that.offset &&
                    position == that.position &&
                    batchSize == that.batchSize &&
                    Objects.equals(channel, thatChannel);
        }

        @Override
        public int hashCode() {
            FileChannel channel = fileRecords == null ? null : fileRecords.channel();

            int result = Long.hashCode(offset);
            result = 31 * result + (channel != null ? channel.hashCode() : 0);
            result = 31 * result + position;
            result = 31 * result + batchSize;
            return result;
        }

        @Override
        public String toString() {
            return "FileChannelRecordBatch(magic: " + magic +
                    ", offset: " + offset +
                    ", size: " + batchSize + ")";
        }
    }
}

相关信息

kafka 源码目录

相关文章

kafka AbstractLegacyRecordBatch 源码

kafka AbstractRecordBatch 源码

kafka AbstractRecords 源码

kafka BaseRecords 源码

kafka ByteBufferLogInputStream 源码

kafka CompressionRatioEstimator 源码

kafka CompressionType 源码

kafka ControlRecordType 源码

kafka ControlRecordUtils 源码

kafka ConvertedRecords 源码