/**
* 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.dfs;
import junit.framework.TestCase;
import java.io.*;
import java.util.Random;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
/**
* This class tests the DFS positional read functionality in a single node
* mini-cluster.
*/
public class TestPread extends TestCase {
static final long seed = 0xDEADBEEFL;
static final int blockSize = 4096;
private void writeFile(FileSystem fileSys, Path name) throws IOException {
// create and write a file that contains three blocks of data
DataOutputStream stm = fileSys.create(name, true, 4096, (short)1,
(long)blockSize);
// test empty file open and read
stm.close();
FSDataInputStream in = fileSys.open(name);
byte[] buffer = new byte[(int)(12*blockSize)];
in.readFully(0, buffer, 0, 0);
IOException res = null;
try { // read beyond the end of the file
in.readFully(0, buffer, 0, 1);
} catch (IOException e) {
// should throw an exception
res = e;
}
assertTrue("Error reading beyond file boundary.", res != null);
in.close();
if (!fileSys.delete(name))
assertTrue("Cannot delete file", false);
// now create the real file
stm = fileSys.create(name, true, 4096, (short)1, (long)blockSize);
Random rand = new Random(seed);
rand.nextBytes(buffer);
stm.write(buffer);
stm.close();
}
private void checkAndEraseData(byte[] actual, int from, byte[] expected, String message) {
for (int idx = 0; idx < actual.length; idx++) {
assertEquals(message+" byte "+(from+idx)+" differs. expected "+
expected[from+idx]+" actual "+actual[idx],
actual[idx], expected[from+idx]);
actual[idx] = 0;
}
}
private void doPread(FSDataInputStream stm, long position, byte[] buffer,
int offset, int length) throws IOException {
int nread = 0;
while (nread < length) {
int nbytes = stm.read(position+nread, buffer, offset+nread, length-nread);
assertTrue("Error in pread", nbytes > 0);
nread += nbytes;
}
}
private void pReadFile(FileSystem fileSys, Path name) throws IOException {
FSDataInputStream stm = fileSys.open(name);
byte[] expected = new byte[(int)(12*blockSize)];
Random rand = new Random(seed);
rand.nextBytes(expected);
// do a sanity check. Read first 4K bytes
byte[] actual = new byte[4096];
stm.readFully(actual);
checkAndEraseData(actual, 0, expected, "Read Sanity Test");
// now do a pread for the first 8K bytes
actual = new byte[8192];
doPread(stm, 0L, actual, 0, 8192);
checkAndEraseData(actual, 0, expected, "Pread Test 1");
// Now check to see if the normal read returns 4K-8K byte range
actual = new byte[4096];
stm.readFully(actual);
checkAndEraseData(actual, 4096, expected, "Pread Test 2");
// Now see if we can cross a single block boundary successfully
// read 4K bytes from blockSize - 2K offset
stm.readFully(blockSize - 2048, actual, 0, 4096);
checkAndEraseData(actual, (int)(blockSize-2048), expected, "Pread Test 3");
// now see if we can cross two block boundaries successfully
// read blockSize + 4K bytes from blockSize - 2K offset
actual = new byte[(int)(blockSize+4096)];
stm.readFully(blockSize - 2048, actual);
checkAndEraseData(actual, (int)(blockSize-2048), expected, "Pread Test 4");
// now see if we can cross two block boundaries that are not cached
// read blockSize + 4K bytes from 10*blockSize - 2K offset
actual = new byte[(int)(blockSize+4096)];
stm.readFully(10*blockSize - 2048, actual);
checkAndEraseData(actual, (int)(10*blockSize-2048), expected, "Pread Test 5");
// now check that even after all these preads, we can still read
// bytes 8K-12K
actual = new byte[4096];
stm.readFully(actual);
checkAndEraseData(actual, 8192, expected, "Pread Test 6");
// done
stm.close();
// check block location caching
stm = fileSys.open(name);
stm.readFully(1, actual, 0, 4096);
stm.readFully(4*blockSize, actual, 0, 4096);
stm.readFully(7*blockSize, actual, 0, 4096);
actual = new byte[3*4096];
stm.readFully(0*blockSize, actual, 0, 3*4096);
checkAndEraseData(actual, 0, expected, "Pread Test 7");
actual = new byte[8*4096];
stm.readFully(3*blockSize, actual, 0, 8*4096);
checkAndEraseData(actual, 3*blockSize, expected, "Pread Test 8");
// read the tail
stm.readFully(11*blockSize+blockSize/2, actual, 0, blockSize/2);
IOException res = null;
try { // read beyond the end of the file
stm.readFully(11*blockSize+blockSize/2, actual, 0, blockSize);
} catch (IOException e) {
// should throw an exception
res = e;
}
assertTrue("Error reading beyond file boundary.", res != null);
stm.close();
}
private void cleanupFile(FileSystem fileSys, Path name) throws IOException {
assertTrue(fileSys.exists(name));
assertTrue(fileSys.delete(name));
assertTrue(!fileSys.exists(name));
}
/**
* Tests positional read in DFS.
*/
public void testPreadDFS() throws IOException {
Configuration conf = new Configuration();
conf.setLong("dfs.block.size", 4096);
conf.setLong("dfs.read.prefetch.size", 4096);
MiniDFSCluster cluster = new MiniDFSCluster(conf, 3, true, null);
FileSystem fileSys = cluster.getFileSystem();
try {
Path file1 = new Path("preadtest.dat");
writeFile(fileSys, file1);
pReadFile(fileSys, file1);
cleanupFile(fileSys, file1);
} finally {
fileSys.close();
cluster.shutdown();
}
}
/**
* Tests positional read in LocalFS.
*/
public void testPreadLocalFS() throws IOException {
Configuration conf = new Configuration();
FileSystem fileSys = FileSystem.getLocal(conf);
try {
Path file1 = new Path("build/test/data", "preadtest.dat");
writeFile(fileSys, file1);
pReadFile(fileSys, file1);
cleanupFile(fileSys, file1);
} finally {
fileSys.close();
}
}
public static void main(String[] args) throws Exception {
new TestPread().testPreadDFS();
}
}