/**
*
* 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.regionserver.wal;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.hbase.codec.Codec;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.io.LimitInputStream;
import org.apache.hadoop.hbase.protobuf.generated.WALProtos;
import org.apache.hadoop.hbase.protobuf.generated.WALProtos.WALHeader.Builder;
import org.apache.hadoop.hbase.protobuf.generated.WALProtos.WALKey;
import org.apache.hadoop.hbase.protobuf.generated.WALProtos.WALTrailer;
import org.apache.hadoop.hbase.util.Bytes;
import com.google.protobuf.CodedInputStream;
import com.google.protobuf.InvalidProtocolBufferException;
/**
* A Protobuf based WAL has the following structure:
* <p>
* <PB_WAL_MAGIC><WALHeader><WALEdits>...<WALEdits><Trailer>
* <TrailerSize> <PB_WAL_COMPLETE_MAGIC>
* </p>
* The Reader reads meta information (WAL Compression state, WALTrailer, etc) in
* {@link ProtobufLogReader#initReader(FSDataInputStream)}. A WALTrailer is an extensible structure
* which is appended at the end of the WAL. This is empty for now; it can contain some meta
* information such as Region level stats, etc in future.
*/
@InterfaceAudience.LimitedPrivate({HBaseInterfaceAudience.COPROC, HBaseInterfaceAudience.PHOENIX})
public class ProtobufLogReader extends ReaderBase {
private static final Log LOG = LogFactory.getLog(ProtobufLogReader.class);
static final byte[] PB_WAL_MAGIC = Bytes.toBytes("PWAL");
static final byte[] PB_WAL_COMPLETE_MAGIC = Bytes.toBytes("LAWP");
protected FSDataInputStream inputStream;
protected Codec.Decoder cellDecoder;
protected WALCellCodec.ByteStringUncompressor byteStringUncompressor;
protected boolean hasCompression = false;
protected boolean hasTagCompression = false;
// walEditsStopOffset is the position of the last byte to read. After reading the last WALEdit entry
// in the hlog, the inputstream's position is equal to walEditsStopOffset.
private long walEditsStopOffset;
private boolean trailerPresent;
private static List<String> writerClsNames = new ArrayList<String>();
static {
writerClsNames.add(ProtobufLogWriter.class.getSimpleName());
}
enum WALHdrResult {
EOF, // stream is at EOF when method starts
SUCCESS,
UNKNOWN_WRITER_CLS // name of writer class isn't recognized
}
// context for WALHdr carrying information such as Cell Codec classname
static class WALHdrContext {
WALHdrResult result;
String cellCodecClsName;
WALHdrContext(WALHdrResult result, String cellCodecClsName) {
this.result = result;
this.cellCodecClsName = cellCodecClsName;
}
WALHdrResult getResult() {
return result;
}
String getCellCodecClsName() {
return cellCodecClsName;
}
}
public ProtobufLogReader() {
super();
}
@Override
public void close() throws IOException {
if (this.inputStream != null) {
this.inputStream.close();
this.inputStream = null;
}
}
@Override
public long getPosition() throws IOException {
return inputStream.getPos();
}
@Override
public void reset() throws IOException {
String clsName = initInternal(null, false);
initAfterCompression(clsName); // We need a new decoder (at least).
}
@Override
protected String initReader(FSDataInputStream stream) throws IOException {
return initInternal(stream, true);
}
/*
* Returns names of the accepted writer classes
*/
protected List<String> getWriterClsNames() {
return writerClsNames;
}
protected WALHdrContext readHeader(Builder builder, FSDataInputStream stream)
throws IOException {
boolean res = builder.mergeDelimitedFrom(stream);
if (!res) return new WALHdrContext(WALHdrResult.EOF, null);
if (builder.hasWriterClsName() &&
!getWriterClsNames().contains(builder.getWriterClsName())) {
return new WALHdrContext(WALHdrResult.UNKNOWN_WRITER_CLS, null);
}
String clsName = null;
if (builder.hasCellCodecClsName()) {
clsName = builder.getCellCodecClsName();
}
return new WALHdrContext(WALHdrResult.SUCCESS, clsName);
}
private String initInternal(FSDataInputStream stream, boolean isFirst)
throws IOException {
close();
long expectedPos = PB_WAL_MAGIC.length;
if (stream == null) {
stream = fs.open(path);
stream.seek(expectedPos);
}
if (stream.getPos() != expectedPos) {
throw new IOException("The stream is at invalid position: " + stream.getPos());
}
// Initialize metadata or, when we reset, just skip the header.
WALProtos.WALHeader.Builder builder = WALProtos.WALHeader.newBuilder();
WALHdrContext hdrCtxt = readHeader(builder, stream);
WALHdrResult walHdrRes = hdrCtxt.getResult();
if (walHdrRes == WALHdrResult.EOF) {
throw new EOFException("Couldn't read WAL PB header");
}
if (walHdrRes == WALHdrResult.UNKNOWN_WRITER_CLS) {
throw new IOException("Got unknown writer class: " + builder.getWriterClsName());
}
if (isFirst) {
WALProtos.WALHeader header = builder.build();
this.hasCompression = header.hasHasCompression() && header.getHasCompression();
this.hasTagCompression = header.hasHasTagCompression() && header.getHasTagCompression();
}
this.inputStream = stream;
this.walEditsStopOffset = this.fileLength;
long currentPosition = stream.getPos();
trailerPresent = setTrailerIfPresent();
this.seekOnFs(currentPosition);
if (LOG.isTraceEnabled()) {
LOG.trace("After reading the trailer: walEditsStopOffset: " + this.walEditsStopOffset
+ ", fileLength: " + this.fileLength + ", " + "trailerPresent: " + trailerPresent);
}
return hdrCtxt.getCellCodecClsName();
}
/**
* To check whether a trailer is present in a WAL, it seeks to position (fileLength -
* PB_WAL_COMPLETE_MAGIC.size() - Bytes.SIZEOF_INT). It reads the int value to know the size of
* the trailer, and checks whether the trailer is present at the end or not by comparing the last
* PB_WAL_COMPLETE_MAGIC.size() bytes. In case trailer is not present, it returns false;
* otherwise, sets the trailer and sets this.walEditsStopOffset variable up to the point just
* before the trailer.
* <ul>
* The trailer is ignored in case:
* <li>fileLength is 0 or not correct (when file is under recovery, etc).
* <li>the trailer size is negative.
* </ul>
* <p>
* In case the trailer size > this.trailerMaxSize, it is read after a WARN message.
* @return true if a valid trailer is present
* @throws IOException
*/
private boolean setTrailerIfPresent() {
try {
long trailerSizeOffset = this.fileLength - (PB_WAL_COMPLETE_MAGIC.length + Bytes.SIZEOF_INT);
if (trailerSizeOffset <= 0) return false;// no trailer possible.
this.seekOnFs(trailerSizeOffset);
// read the int as trailer size.
int trailerSize = this.inputStream.readInt();
ByteBuffer buf = ByteBuffer.allocate(ProtobufLogReader.PB_WAL_COMPLETE_MAGIC.length);
this.inputStream.readFully(buf.array(), buf.arrayOffset(), buf.capacity());
if (!Arrays.equals(buf.array(), PB_WAL_COMPLETE_MAGIC)) {
LOG.trace("No trailer found.");
return false;
}
if (trailerSize < 0) {
LOG.warn("Invalid trailer Size " + trailerSize + ", ignoring the trailer");
return false;
} else if (trailerSize > this.trailerWarnSize) {
// continue reading after warning the user.
LOG.warn("Please investigate WALTrailer usage. Trailer size > maximum configured size : "
+ trailerSize + " > " + this.trailerWarnSize);
}
// seek to the position where trailer starts.
long positionOfTrailer = trailerSizeOffset - trailerSize;
this.seekOnFs(positionOfTrailer);
// read the trailer.
buf = ByteBuffer.allocate(trailerSize);// for trailer.
this.inputStream.readFully(buf.array(), buf.arrayOffset(), buf.capacity());
trailer = WALTrailer.parseFrom(buf.array());
this.walEditsStopOffset = positionOfTrailer;
return true;
} catch (IOException ioe) {
LOG.warn("Got IOE while reading the trailer. Continuing as if no trailer is present.", ioe);
}
return false;
}
protected WALCellCodec getCodec(Configuration conf, String cellCodecClsName,
CompressionContext compressionContext) throws IOException {
return WALCellCodec.create(conf, cellCodecClsName, compressionContext);
}
@Override
protected void initAfterCompression() throws IOException {
initAfterCompression(null);
}
@Override
protected void initAfterCompression(String cellCodecClsName) throws IOException {
WALCellCodec codec = getCodec(this.conf, cellCodecClsName, this.compressionContext);
this.cellDecoder = codec.getDecoder(this.inputStream);
if (this.hasCompression) {
this.byteStringUncompressor = codec.getByteStringUncompressor();
}
}
@Override
protected boolean hasCompression() {
return this.hasCompression;
}
@Override
protected boolean hasTagCompression() {
return this.hasTagCompression;
}
@Override
protected boolean readNext(HLog.Entry entry) throws IOException {
while (true) {
// OriginalPosition might be < 0 on local fs; if so, it is useless to us.
long originalPosition = this.inputStream.getPos();
if (trailerPresent && originalPosition > 0 && originalPosition == this.walEditsStopOffset) {
return false;
}
WALKey.Builder builder = WALKey.newBuilder();
long size = 0;
try {
long available = -1;
try {
int firstByte = this.inputStream.read();
if (firstByte == -1) {
throw new EOFException("First byte is negative");
}
size = CodedInputStream.readRawVarint32(firstByte, this.inputStream);
// available may be < 0 on local fs for instance. If so, can't depend on it.
available = this.inputStream.available();
if (available > 0 && available < size) {
throw new EOFException("Available stream not enough for edit, " +
"inputStream.available()= " + this.inputStream.available() + ", " +
"entry size= " + size);
}
final InputStream limitedInput = new LimitInputStream(this.inputStream, size);
builder.mergeFrom(limitedInput);
} catch (InvalidProtocolBufferException ipbe) {
throw (EOFException) new EOFException("Invalid PB, EOF? Ignoring; originalPosition=" +
originalPosition + ", currentPosition=" + this.inputStream.getPos() +
", messageSize=" + size + ", currentAvailable=" + available).initCause(ipbe);
}
if (!builder.isInitialized()) {
// TODO: not clear if we should try to recover from corrupt PB that looks semi-legit.
// If we can get the KV count, we could, theoretically, try to get next record.
throw new EOFException("Partial PB while reading WAL, " +
"probably an unexpected EOF, ignoring");
}
WALKey walKey = builder.build();
entry.getKey().readFieldsFromPb(walKey, this.byteStringUncompressor);
if (!walKey.hasFollowingKvCount() || 0 == walKey.getFollowingKvCount()) {
LOG.trace("WALKey has no KVs that follow it; trying the next one");
continue;
}
int expectedCells = walKey.getFollowingKvCount();
long posBefore = this.inputStream.getPos();
try {
int actualCells = entry.getEdit().readFromCells(cellDecoder, expectedCells);
if (expectedCells != actualCells) {
throw new EOFException("Only read " + actualCells); // other info added in catch
}
} catch (Exception ex) {
String posAfterStr = "<unknown>";
try {
posAfterStr = this.inputStream.getPos() + "";
} catch (Throwable t) {
LOG.trace("Error getting pos for error message - ignoring", t);
}
String message = " while reading " + expectedCells + " WAL KVs; started reading at "
+ posBefore + " and read up to " + posAfterStr;
IOException realEofEx = extractHiddenEof(ex);
throw (EOFException) new EOFException("EOF " + message).
initCause(realEofEx != null ? realEofEx : ex);
}
if (trailerPresent && this.inputStream.getPos() > this.walEditsStopOffset) {
LOG.error("Read WALTrailer while reading WALEdits. hlog: " + this.path
+ ", inputStream.getPos(): " + this.inputStream.getPos() + ", walEditsStopOffset: "
+ this.walEditsStopOffset);
throw new EOFException("Read WALTrailer while reading WALEdits");
}
} catch (EOFException eof) {
LOG.trace("Encountered a malformed edit, seeking back to last good position in file", eof);
// If originalPosition is < 0, it is rubbish and we cannot use it (probably local fs)
if (originalPosition < 0) throw eof;
// Else restore our position to original location in hope that next time through we will
// read successfully.
seekOnFs(originalPosition);
return false;
}
return true;
}
}
private IOException extractHiddenEof(Exception ex) {
// There are two problems we are dealing with here. Hadoop stream throws generic exception
// for EOF, not EOFException; and scanner further hides it inside RuntimeException.
IOException ioEx = null;
if (ex instanceof EOFException) {
return (EOFException)ex;
} else if (ex instanceof IOException) {
ioEx = (IOException)ex;
} else if (ex instanceof RuntimeException
&& ex.getCause() != null && ex.getCause() instanceof IOException) {
ioEx = (IOException)ex.getCause();
}
if (ioEx != null) {
if (ioEx.getMessage().contains("EOF")) return ioEx;
return null;
}
return null;
}
@Override
public WALTrailer getWALTrailer() {
return trailer;
}
@Override
protected void seekOnFs(long pos) throws IOException {
this.inputStream.seek(pos);
}
}