Java tutorial
/** * Copyright (c) 2016. Qubole Inc * Licensed 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. See accompanying LICENSE file. */ package com.qubole.rubix.core; import com.google.common.base.Throwables; import com.qubole.rubix.bookkeeper.RetryingBookkeeperClient; 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 java.io.IOException; import java.io.RandomAccessFile; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import static com.google.common.base.Preconditions.checkState; import static com.qubole.rubix.bookkeeper.RetryingBookkeeperClient.createBookKeeperClient; /** * Created by stagra on 4/1/16. * * This chain reads from Remote and stores one copy in cache */ public class RemoteReadRequestChain extends ReadRequestChain { final FSDataInputStream inputStream; final String localFilename; private int totalPrefixRead = 0; private int totalSuffixRead = 0; private int totalRequestedRead = 0; private long warmupPenalty = 0; private static final Log log = LogFactory.getLog(RemoteReadRequestChain.class); public RemoteReadRequestChain(FSDataInputStream inputStream, String localFile) { this.inputStream = inputStream; this.localFilename = localFile; } public Integer call() throws IOException { Thread.currentThread().setName(threadName); checkState(isLocked, "Trying to execute Chain without locking"); if (readRequests.size() == 0) { return 0; } RandomAccessFile localFile = null; FileChannel fc = null; try { localFile = new RandomAccessFile(localFilename, "rw"); fc = localFile.getChannel(); for (ReadRequest readRequest : readRequests) { log.debug(String.format("Executing ReadRequest: [%d, %d, %d, %d, %d]", readRequest.getBackendReadStart(), readRequest.getBackendReadEnd(), readRequest.getActualReadStart(), readRequest.getActualReadEnd(), readRequest.getDestBufferOffset())); inputStream.seek(readRequest.backendReadStart); MappedByteBuffer mbuf = fc.map(FileChannel.MapMode.READ_WRITE, readRequest.backendReadStart, readRequest.getBackendReadLength()); log.debug(String.format("Mapped file from %d till length %d", readRequest.backendReadStart, readRequest.getBackendReadLength())); /* * MappedByteBuffer does not provide backing byte array, so cannot write directly to it via FSDataOutputStream.read * Instead, download to normal destination buffer (+offset buffer to get block boundaries) and then copy to MappedByteBuffer */ int prefixBufferLength = (int) (readRequest.getActualReadStart() - readRequest.getBackendReadStart()); int suffixBufferLength = (int) (readRequest.getBackendReadEnd() - readRequest.getActualReadEnd()); log.debug( String.format("PrefixLength: %d SuffixLength: %d", prefixBufferLength, suffixBufferLength)); // TODO: use single byte buffer for all three streams /* TODO: also GC cost can be lowered by shared buffer pool, a small one. IOUtils.copyLarge method. A single 4kB byte buffer can be used to copy whole file */ if (prefixBufferLength > 0) { byte[] prefixBuffer = new byte[prefixBufferLength]; log.debug(String.format("Trying to Read %d bytes into prefix buffer", prefixBufferLength)); totalPrefixRead += readAndCopy(prefixBuffer, 0, mbuf, prefixBufferLength); log.debug(String.format("Read %d bytes into prefix buffer", prefixBufferLength)); } log.debug(String.format("Trying to Read %d bytes into destination buffer", readRequest.getActualReadLength())); int readBytes = readAndCopy(readRequest.getDestBuffer(), readRequest.destBufferOffset, mbuf, readRequest.getActualReadLength()); totalRequestedRead += readBytes; log.debug(String.format("Read %d bytes into destination buffer", readBytes)); if (suffixBufferLength > 0) { // If already in reading actually required data we get a eof, then there should not have been a suffix request checkState(readBytes == readRequest.getActualReadLength(), "Acutal read less than required, still requested for suffix"); byte[] suffixBuffer = new byte[suffixBufferLength]; log.debug(String.format("Trying to Read %d bytes into suffix buffer", suffixBufferLength)); totalSuffixRead += readAndCopy(suffixBuffer, 0, mbuf, suffixBufferLength); log.debug(String.format("Read %d bytes into suffix buffer", suffixBufferLength)); } } } finally { if (fc != null) { fc.close(); } if (localFile != null) { localFile.close(); } } log.info(String.format("Read %d bytes from remote file, added %d to destination buffer", totalPrefixRead + totalRequestedRead + totalSuffixRead, totalRequestedRead)); return totalRequestedRead; } private int readAndCopy(byte[] destBuffer, int destBufferOffset, MappedByteBuffer localFileBuffer, int length) throws IOException { int nread = 0; while (nread < length) { int nbytes = inputStream.read(destBuffer, destBufferOffset + nread, length - nread); if (nbytes < 0) { return nread; } nread += nbytes; } long start = System.nanoTime(); localFileBuffer.put(destBuffer, destBufferOffset, length); warmupPenalty += System.nanoTime() - start; return nread; } public ReadRequestChainStats getStats() { return new ReadRequestChainStats().setPrefixRead(totalPrefixRead).setRequestedRead(totalRequestedRead) .setSuffixRead(totalSuffixRead).setWarmupPenalty(warmupPenalty).setRemoteReads(requests); } @Override public void updateCacheStatus(String remotePath, long fileSize, long lastModified, int blockSize, Configuration conf) { try { RetryingBookkeeperClient client = createBookKeeperClient(conf); for (ReadRequest readRequest : readRequests) { client.setAllCached(remotePath, fileSize, lastModified, toBlock(readRequest.getBackendReadStart(), blockSize), toBlock(readRequest.getBackendReadEnd() - 1, blockSize) + 1); } client.close(); } catch (Exception e) { log.info("Could not update BookKeeper about newly cached blocks: " + Throwables.getStackTraceAsString(e)); } } private long toBlock(long pos, int blockSize) { return pos / blockSize; } }