org.apache.hadoop.hdfs.nfs.nfs3.WriteCtx Maven / Gradle / Ivy
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* 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.hdfs.nfs.nfs3;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.hdfs.client.HdfsDataOutputStream;
import org.apache.hadoop.nfs.nfs3.FileHandle;
import org.apache.hadoop.nfs.nfs3.Nfs3Constant.WriteStableHow;
import org.jboss.netty.channel.Channel;
import org.apache.hadoop.thirdparty.com.google.common.annotations.VisibleForTesting;
import org.apache.hadoop.thirdparty.com.google.common.base.Preconditions;
/**
* WriteCtx saves the context of one write request, such as request, channel,
* xid and reply status.
*/
class WriteCtx {
public static final Logger LOG = LoggerFactory.getLogger(WriteCtx.class);
/**
* In memory write data has 3 states. ALLOW_DUMP: not sequential write, still
* wait for prerequisite writes. NO_DUMP: sequential write, no need to dump
* since it will be written to HDFS soon. DUMPED: already dumped to a file.
*/
public enum DataState {
ALLOW_DUMP,
NO_DUMP,
DUMPED
}
private final FileHandle handle;
private long offset;
private int count;
/**
* Some clients can send a write that includes previously written data along
* with new data. In such case the write request is changed to write from only
* the new data. {@code originalCount} tracks the number of bytes sent in the
* request before it was modified to write only the new data.
* @see OpenFileCtx#addWritesToCache for more details
*/
private int originalCount;
public static final int INVALID_ORIGINAL_COUNT = -1;
/**
* Overlapping Write Request Handling
* A write request can be in three states:
* s0. just created, with data != null
* s1. dumped as length "count", and data set to null
* s2. read back from dumped area as length "count"
*
* Write requests may have overlapping range, we detect this by comparing
* the data offset range of the request against the current offset of data
* already written to HDFS. There are two categories:
*
* 1. If the beginning part of a new write request data is already written
* due to an earlier request, we alter the new request by trimming this
* portion before the new request enters state s0, and the originalCount is
* remembered.
*
* 2. If the lower end of the write request range is beyond the current
* offset of data already written, we put the request into cache, and detect
* the overlapping when taking the request out from cache.
*
* For category 2, if we find out that a write request overlap with another,
* this write request is already in state s0, s1, or s3. We trim the
* beginning part of this request, by remembering the size of this portion
* as trimDelta. So the resulted offset of the write request is
* "offset + trimDelta" and the resulted size of the write request is
* "count - trimDelta".
*
* What important to notice is, if the request is in s1 when we do the
* trimming, the data dumped is of size "count", so when we load
* the data back from dumped area, we should set the position of the data
* buffer to trimDelta.
*/
private int trimDelta;
public synchronized int getOriginalCount() {
return originalCount;
}
public void trimWrite(int delta) {
Preconditions.checkState(delta < count);
if (LOG.isDebugEnabled()) {
LOG.debug("Trim write request by delta:" + delta + " " + toString());
}
synchronized(this) {
trimDelta = delta;
if (originalCount == INVALID_ORIGINAL_COUNT) {
originalCount = count;
}
trimData();
}
}
private final WriteStableHow stableHow;
private volatile ByteBuffer data;
private final Channel channel;
private final int xid;
private boolean replied;
/**
* Data belonging to the same {@link OpenFileCtx} may be dumped to a file.
* After being dumped to the file, the corresponding {@link WriteCtx} records
* the dump file and the offset.
*/
private RandomAccessFile raf;
private long dumpFileOffset;
private volatile DataState dataState;
public final long startTime;
public DataState getDataState() {
return dataState;
}
public void setDataState(DataState dataState) {
this.dataState = dataState;
}
/**
* Writing the data into a local file. After the writing, if
* {@link #dataState} is still ALLOW_DUMP, set {@link #data} to null and set
* {@link #dataState} to DUMPED.
*/
long dumpData(FileOutputStream dumpOut, RandomAccessFile raf)
throws IOException {
if (dataState != DataState.ALLOW_DUMP) {
if (LOG.isTraceEnabled()) {
LOG.trace("No need to dump with status(replied,dataState):" + "("
+ replied + "," + dataState + ")");
}
return 0;
}
// Resized write should not allow dump
Preconditions.checkState(getOriginalCount() == INVALID_ORIGINAL_COUNT);
this.raf = raf;
dumpFileOffset = dumpOut.getChannel().position();
dumpOut.write(data.array(), 0, count);
if (LOG.isDebugEnabled()) {
LOG.debug("After dump, new dumpFileOffset:" + dumpFileOffset);
}
// it is possible that while we dump the data, the data is also being
// written back to HDFS. After dump, if the writing back has not finished
// yet, we change its flag to DUMPED and set the data to null. Otherwise
// this WriteCtx instance should have been removed from the buffer.
if (dataState == DataState.ALLOW_DUMP) {
synchronized (this) {
if (dataState == DataState.ALLOW_DUMP) {
data = null;
dataState = DataState.DUMPED;
return count;
}
}
}
return 0;
}
FileHandle getHandle() {
return handle;
}
long getOffset() {
synchronized(this) {
// See comment "Overlapping Write Request Handling" above
return offset + trimDelta;
}
}
/**
* @return the offset field
*/
private synchronized long getPlainOffset() {
return offset;
}
int getCount() {
synchronized(this) {
// See comment "Overlapping Write Request Handling" above
return count - trimDelta;
}
}
WriteStableHow getStableHow() {
return stableHow;
}
@VisibleForTesting
ByteBuffer getData() throws IOException {
if (dataState != DataState.DUMPED) {
synchronized (this) {
if (dataState != DataState.DUMPED) {
Preconditions.checkState(data != null);
return data;
}
}
}
// read back from dumped file
this.loadData();
return data;
}
private void loadData() throws IOException {
Preconditions.checkState(data == null);
byte[] rawData = new byte[count];
raf.seek(dumpFileOffset);
int size = raf.read(rawData, 0, count);
if (size != count) {
throw new IOException("Data count is " + count + ", but read back "
+ size + "bytes");
}
synchronized(this) {
data = ByteBuffer.wrap(rawData);
trimData();
}
}
private void trimData() {
if (data != null && trimDelta > 0) {
// make it not dump-able since the data will be used
// shortly
dataState = DataState.NO_DUMP;
data.position(data.position() + trimDelta);
offset += trimDelta;
count -= trimDelta;
trimDelta = 0;
}
}
public void writeData(HdfsDataOutputStream fos) throws IOException {
Preconditions.checkState(fos != null);
ByteBuffer dataBuffer;
try {
dataBuffer = getData();
} catch (Exception e1) {
LOG.error("Failed to get request data offset:" + getPlainOffset() + " " +
"count:" + count + " error:" + e1);
throw new IOException("Can't get WriteCtx.data");
}
byte[] data = dataBuffer.array();
int position = dataBuffer.position();
int limit = dataBuffer.limit();
Preconditions.checkState(limit - position == count);
// Modified write has a valid original count
if (position != 0) {
if (limit != getOriginalCount()) {
throw new IOException("Modified write has differnt original size."
+ "buff position:" + position + " buff limit:" + limit + ". "
+ toString());
}
}
// Now write data
fos.write(data, position, count);
}
Channel getChannel() {
return channel;
}
int getXid() {
return xid;
}
boolean getReplied() {
return replied;
}
void setReplied(boolean replied) {
this.replied = replied;
}
WriteCtx(FileHandle handle, long offset, int count, int originalCount,
WriteStableHow stableHow, ByteBuffer data, Channel channel, int xid,
boolean replied, DataState dataState) {
this.handle = handle;
this.offset = offset;
this.count = count;
this.originalCount = originalCount;
this.trimDelta = 0;
this.stableHow = stableHow;
this.data = data;
this.channel = channel;
this.xid = xid;
this.replied = replied;
this.dataState = dataState;
raf = null;
this.startTime = System.nanoTime();
}
@Override
public String toString() {
return "FileHandle:" + handle.dumpFileHandle() + " offset:"
+ getPlainOffset() + " " + "count:" + count + " originalCount:"
+ getOriginalCount() + " stableHow:" + stableHow + " replied:"
+ replied + " dataState:" + dataState + " xid:" + xid;
}
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