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Main functionality for HBase
/*
* 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.hadoop.hbase.io.hfile;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.ChecksumException;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.util.ChecksumType;
import org.apache.hadoop.util.DataChecksum;
/**
* Utility methods to compute and validate checksums.
*/
@InterfaceAudience.Private
public class ChecksumUtil {
public static final Log LOG = LogFactory.getLog(ChecksumUtil.class);
/** This is used to reserve space in a byte buffer */
private static byte[] DUMMY_VALUE = new byte[128 * HFileBlock.CHECKSUM_SIZE];
/**
* This is used by unit tests to make checksum failures throw an
* exception instead of returning null. Returning a null value from
* checksum validation will cause the higher layer to retry that
* read with hdfs-level checksums. Instead, we would like checksum
* failures to cause the entire unit test to fail.
*/
private static boolean generateExceptions = false;
/**
* Generates a checksum for all the data in indata. The checksum is
* written to outdata.
* @param indata input data stream
* @param startOffset starting offset in the indata stream from where to
* compute checkums from
* @param endOffset ending offset in the indata stream upto
* which checksums needs to be computed
* @param outdata the output buffer where checksum values are written
* @param outOffset the starting offset in the outdata where the
* checksum values are written
* @param checksumType type of checksum
* @param bytesPerChecksum number of bytes per checksum value
*/
static void generateChecksums(byte[] indata, int startOffset, int endOffset,
byte[] outdata, int outOffset, ChecksumType checksumType,
int bytesPerChecksum) throws IOException {
if (checksumType == ChecksumType.NULL) {
return; // No checksum for this block.
}
DataChecksum checksum = DataChecksum.newDataChecksum(
checksumType.getDataChecksumType(), bytesPerChecksum);
checksum.calculateChunkedSums(
ByteBuffer.wrap(indata, startOffset, endOffset - startOffset),
ByteBuffer.wrap(outdata, outOffset, outdata.length - outOffset));
}
/**
* Validates that the data in the specified HFileBlock matches the checksum. Generates the
* checksums for the data and then validate that it matches those stored in the end of the data.
* @param buffer Contains the data in following order: HFileBlock header, data, checksums.
* @param pathName Path of the HFile to which the {@code data} belongs. Only used for logging.
* @param offset offset of the data being validated. Only used for logging.
* @param hdrSize Size of the block header in {@code data}. Only used for logging.
* @return True if checksum matches, else false.
*/
static boolean validateChecksum(ByteBuffer buffer, String pathName, long offset, int hdrSize)
throws IOException {
// A ChecksumType.NULL indicates that the caller is not interested in validating checksums,
// so we always return true.
ChecksumType cktype =
ChecksumType.codeToType(buffer.get(HFileBlock.Header.CHECKSUM_TYPE_INDEX));
if (cktype == ChecksumType.NULL) {
return true; // No checksum validations needed for this block.
}
// read in the stored value of the checksum size from the header.
int bytesPerChecksum = buffer.getInt(HFileBlock.Header.BYTES_PER_CHECKSUM_INDEX);
DataChecksum dataChecksum = DataChecksum.newDataChecksum(
cktype.getDataChecksumType(), bytesPerChecksum);
assert dataChecksum != null;
int onDiskDataSizeWithHeader =
buffer.getInt(HFileBlock.Header.ON_DISK_DATA_SIZE_WITH_HEADER_INDEX);
if (LOG.isTraceEnabled()) {
LOG.info("dataLength=" + buffer.capacity()
+ ", sizeWithHeader=" + onDiskDataSizeWithHeader
+ ", checksumType=" + cktype.getName()
+ ", file=" + pathName
+ ", offset=" + offset
+ ", headerSize=" + hdrSize
+ ", bytesPerChecksum=" + bytesPerChecksum);
}
try {
ByteBuffer data = (ByteBuffer) buffer.duplicate().position(0).limit(onDiskDataSizeWithHeader);
ByteBuffer checksums = (ByteBuffer) buffer.duplicate().position(onDiskDataSizeWithHeader)
.limit(buffer.capacity());
dataChecksum.verifyChunkedSums(data, checksums, pathName, 0);
} catch (ChecksumException e) {
return false;
}
return true; // checksum is valid
}
/**
* Returns the number of bytes needed to store the checksums for
* a specified data size
* @param datasize number of bytes of data
* @param bytesPerChecksum number of bytes in a checksum chunk
* @return The number of bytes needed to store the checksum values
*/
static long numBytes(long datasize, int bytesPerChecksum) {
return numChunks(datasize, bytesPerChecksum) * HFileBlock.CHECKSUM_SIZE;
}
/**
* Returns the number of checksum chunks needed to store the checksums for
* a specified data size
* @param datasize number of bytes of data
* @param bytesPerChecksum number of bytes in a checksum chunk
* @return The number of checksum chunks
*/
static long numChunks(long datasize, int bytesPerChecksum) {
long numChunks = datasize/bytesPerChecksum;
if (datasize % bytesPerChecksum != 0) {
numChunks++;
}
return numChunks;
}
/**
* Write dummy checksums to the end of the specified bytes array
* to reserve space for writing checksums later
* @param baos OutputStream to write dummy checkum values
* @param numBytes Number of bytes of data for which dummy checksums
* need to be generated
* @param bytesPerChecksum Number of bytes per checksum value
*/
static void reserveSpaceForChecksums(ByteArrayOutputStream baos,
int numBytes, int bytesPerChecksum) throws IOException {
long numChunks = numChunks(numBytes, bytesPerChecksum);
long bytesLeft = numChunks * HFileBlock.CHECKSUM_SIZE;
while (bytesLeft > 0) {
long count = Math.min(bytesLeft, DUMMY_VALUE.length);
baos.write(DUMMY_VALUE, 0, (int)count);
bytesLeft -= count;
}
}
/**
* Mechanism to throw an exception in case of hbase checksum
* failure. This is used by unit tests only.
* @param value Setting this to true will cause hbase checksum
* verification failures to generate exceptions.
*/
public static void generateExceptionForChecksumFailureForTest(boolean value) {
generateExceptions = value;
}
}