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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.regionserver.wal;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.NavigableMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.wal.WAL.Entry;
import org.apache.hadoop.hdfs.client.HdfsDataInputStream;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.SequenceFile.Metadata;
import org.apache.hadoop.io.Text;
@InterfaceAudience.LimitedPrivate({HBaseInterfaceAudience.COPROC, HBaseInterfaceAudience.PHOENIX,
HBaseInterfaceAudience.CONFIG})
public class SequenceFileLogReader extends ReaderBase {
private static final Log LOG = LogFactory.getLog(SequenceFileLogReader.class);
// Legacy stuff from pre-PB WAL metadata.
private static final Text WAL_VERSION_KEY = new Text("version");
// Let the version be 1. Let absence of a version meta tag be old, version 0.
// Set this version '1' to be the version that introduces compression,
// the COMPRESSION_VERSION.
private static final int COMPRESSION_VERSION = 1;
private static final Text WAL_COMPRESSION_TYPE_KEY = new Text("compression.type");
private static final Text DICTIONARY_COMPRESSION_TYPE = new Text("dictionary");
/**
* Hack just to set the correct file length up in SequenceFile.Reader.
* See HADOOP-6307. The below is all about setting the right length on the
* file we are reading. fs.getFileStatus(file).getLen() is passed down to
* a private SequenceFile.Reader constructor. This won't work. Need to do
* the available on the stream. The below is ugly. It makes getPos, the
* first time its called, return length of the file -- i.e. tell a lie -- just
* so this line up in SF.Reader's constructor ends up with right answer:
*
* this.end = in.getPos() + length;
*
*/
private static class WALReader extends SequenceFile.Reader {
WALReader(final FileSystem fs, final Path p, final Configuration c)
throws IOException {
super(fs, p, c);
}
@Override
protected FSDataInputStream openFile(FileSystem fs, Path file,
int bufferSize, long length)
throws IOException {
return new WALReaderFSDataInputStream(super.openFile(fs, file,
bufferSize, length), length);
}
/**
* Override just so can intercept first call to getPos.
*/
static class WALReaderFSDataInputStream extends FSDataInputStream {
private boolean firstGetPosInvocation = true;
private long length;
WALReaderFSDataInputStream(final FSDataInputStream is, final long l)
throws IOException {
super(is);
this.length = l;
}
// This section can be confusing. It is specific to how HDFS works.
// Let me try to break it down. This is the problem:
//
// 1. HDFS DataNodes update the NameNode about a filename's length
// on block boundaries or when a file is closed. Therefore,
// if an RS dies, then the NN's fs.getLength() can be out of date
// 2. this.in.available() would work, but it returns int &
// therefore breaks for files > 2GB (happens on big clusters)
// 3. DFSInputStream.getFileLength() gets the actual length from the DNs
// 4. DFSInputStream is wrapped 2 levels deep : this.in.in
//
// So, here we adjust getPos() using getFileLength() so the
// SequenceFile.Reader constructor (aka: first invocation) comes out
// with the correct end of the file:
// this.end = in.getPos() + length;
@Override
public long getPos() throws IOException {
if (this.firstGetPosInvocation) {
this.firstGetPosInvocation = false;
long adjust = 0;
HdfsDataInputStream hdfsDataInputStream = null;
try {
if (this.in.getClass().getName().endsWith("HdfsDataInputStream")
|| this.in.getClass().getName().endsWith("DFSInputStream")) {
hdfsDataInputStream = (HdfsDataInputStream) this.getWrappedStream();
long realLength = hdfsDataInputStream.getVisibleLength();
assert(realLength >= this.length);
adjust = realLength - this.length;
} else {
LOG.info(
"Input stream class: " + this.in.getClass().getName() + ", not adjusting length");
}
} catch (Exception e) {
LOG.warn("Error while trying to get accurate file length. "
+ "Truncation / data loss may occur if RegionServers die.",
e);
throw new IOException(e);
}
return adjust + super.getPos();
}
return super.getPos();
}
}
}
// Protected for tests.
protected SequenceFile.Reader reader;
long entryStart = 0; // needed for logging exceptions
public SequenceFileLogReader() {
super();
}
@Override
public void close() throws IOException {
try {
if (reader != null) {
this.reader.close();
this.reader = null;
}
} catch (IOException ioe) {
throw addFileInfoToException(ioe);
}
}
@Override
public long getPosition() throws IOException {
return reader != null ? reader.getPosition() : 0;
}
@Override
public void reset() throws IOException {
// Resetting the reader lets us see newly added data if the file is being written to
// We also keep the same compressionContext which was previously populated for this file
reader = new WALReader(fs, path, conf);
}
@Override
protected String initReader(FSDataInputStream stream) throws IOException {
// We don't use the stream because we have to have the magic stream above.
if (stream != null) {
stream.close();
}
reset();
return null;
}
@Override
protected void initAfterCompression(String cellCodecClsName) throws IOException {
// Nothing to do here
}
@Override
protected void initAfterCompression() throws IOException {
// Nothing to do here
}
@Override
protected boolean hasCompression() {
return isWALCompressionEnabled(reader.getMetadata());
}
@Override
protected boolean hasTagCompression() {
// Tag compression not supported with old SequenceFileLog Reader/Writer
return false;
}
/**
* Call this method after init() has been executed
* @return whether WAL compression is enabled
*/
static boolean isWALCompressionEnabled(final Metadata metadata) {
// Check version is >= VERSION?
Text txt = metadata.get(WAL_VERSION_KEY);
if (txt == null || Integer.parseInt(txt.toString()) < COMPRESSION_VERSION) {
return false;
}
// Now check that compression type is present. Currently only one value.
txt = metadata.get(WAL_COMPRESSION_TYPE_KEY);
return txt != null && txt.equals(DICTIONARY_COMPRESSION_TYPE);
}
/**
* fill in the passed entry with teh next key/value.
* Note that because this format deals with our legacy storage, the provided
* Entery MUST use an {@link HLogKey} for the key.
* @return boolean indicating if the contents of Entry have been filled in.
*/
@Override
protected boolean readNext(Entry e) throws IOException {
try {
if (!(e.getKey() instanceof HLogKey)) {
final IllegalArgumentException exception = new IllegalArgumentException(
"SequenceFileLogReader only works when given entries that have HLogKey for keys. This" +
" one had '" + e.getKey().getClass() + "'");
LOG.error("We need to use the legacy SequenceFileLogReader to handle a " +
" pre-0.96 style WAL, but HBase internals failed to use the deprecated HLogKey class." +
" This is a bug; please file an issue or email the developer mailing list. You will " +
"need the following exception details when seeking help from the HBase community.",
exception);
throw exception;
}
boolean hasNext = this.reader.next((HLogKey)e.getKey(), e.getEdit());
if (!hasNext) return false;
// Scopes are probably in WAL edit, move to key
NavigableMap scopes = e.getEdit().getAndRemoveScopes();
if (scopes != null) {
e.getKey().readOlderScopes(scopes);
}
return true;
} catch (IOException ioe) {
throw addFileInfoToException(ioe);
}
}
@Override
protected void seekOnFs(long pos) throws IOException {
try {
reader.seek(pos);
} catch (IOException ioe) {
throw addFileInfoToException(ioe);
}
}
protected IOException addFileInfoToException(final IOException ioe)
throws IOException {
long pos = -1;
try {
pos = getPosition();
} catch (IOException e) {
LOG.warn("Failed getting position to add to throw", e);
}
// See what SequenceFile.Reader thinks is the end of the file
long end = Long.MAX_VALUE;
try {
Field fEnd = SequenceFile.Reader.class.getDeclaredField("end");
fEnd.setAccessible(true);
end = fEnd.getLong(this.reader);
} catch(NoSuchFieldException nfe) {
/* reflection failure, keep going */
if (LOG.isTraceEnabled()) LOG.trace(nfe);
} catch(IllegalAccessException iae) {
/* reflection failure, keep going */
if (LOG.isTraceEnabled()) LOG.trace(iae);
} catch(Exception e) {
/* All other cases. Should we handle it more aggressively? */
LOG.warn("Unexpected exception when accessing the end field", e);
}
String msg = (this.path == null? "": this.path.toString()) +
", entryStart=" + entryStart + ", pos=" + pos +
((end == Long.MAX_VALUE) ? "" : ", end=" + end) +
", edit=" + this.edit;
// Enhance via reflection so we don't change the original class type
try {
return (IOException) ioe.getClass()
.getConstructor(String.class)
.newInstance(msg)
.initCause(ioe);
} catch(NoSuchMethodException nfe) {
/* reflection failure, keep going */
if (LOG.isTraceEnabled()) LOG.trace(nfe);
} catch(IllegalAccessException iae) {
/* reflection failure, keep going */
if (LOG.isTraceEnabled()) LOG.trace(iae);
} catch(Exception e) {
/* All other cases. Should we handle it more aggressively? */
LOG.warn("Unexpected exception when accessing the end field", e);
}
return ioe;
}
}