| /** |
| * 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.distributedlog; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| import java.io.IOException; |
| import java.io.InputStream; |
| |
| import org.apache.distributedlog.api.DistributedLogManager; |
| import org.apache.distributedlog.api.LogReader; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * AppendOnlyStreamReader. |
| */ |
| public class AppendOnlyStreamReader extends InputStream { |
| static final Logger LOG = LoggerFactory.getLogger(AppendOnlyStreamReader.class); |
| |
| private LogRecordWithInputStream currentLogRecord = null; |
| private final DistributedLogManager dlm; |
| private LogReader reader; |
| private long currentPosition; |
| private static final int SKIP_BUFFER_SIZE = 512; |
| |
| // Cache the input stream for a log record. |
| private static class LogRecordWithInputStream { |
| private final InputStream payloadStream; |
| private final LogRecordWithDLSN logRecord; |
| |
| LogRecordWithInputStream(LogRecordWithDLSN logRecord) { |
| checkNotNull(logRecord); |
| |
| LOG.debug("Got record dlsn = {}, txid = {}, len = {}", |
| new Object[] {logRecord.getDlsn(), logRecord.getTransactionId(), logRecord.getPayload().length}); |
| |
| this.logRecord = logRecord; |
| this.payloadStream = logRecord.getPayLoadInputStream(); |
| } |
| |
| InputStream getPayLoadInputStream() { |
| return payloadStream; |
| } |
| |
| LogRecordWithDLSN getLogRecord() { |
| return logRecord; |
| } |
| |
| // The last txid of the log record is the position of the next byte in the stream. |
| // Subtract length to get starting offset. |
| long getOffset() { |
| return logRecord.getTransactionId() - logRecord.getPayload().length; |
| } |
| } |
| |
| /** |
| * Construct ledger input stream. |
| * |
| * @param dlm the Distributed Log Manager to access the stream |
| */ |
| AppendOnlyStreamReader(DistributedLogManager dlm) |
| throws IOException { |
| this.dlm = dlm; |
| reader = dlm.getInputStream(0); |
| currentPosition = 0; |
| } |
| |
| /** |
| * Get input stream representing next entry in the |
| * ledger. |
| * |
| * @return input stream, or null if no more entries |
| */ |
| private LogRecordWithInputStream nextLogRecord() throws IOException { |
| return nextLogRecord(reader); |
| } |
| |
| private static LogRecordWithInputStream nextLogRecord(LogReader reader) throws IOException { |
| LogRecordWithDLSN record = reader.readNext(false); |
| |
| if (null != record) { |
| return new LogRecordWithInputStream(record); |
| } else { |
| record = reader.readNext(false); |
| if (null != record) { |
| return new LogRecordWithInputStream(record); |
| } else { |
| LOG.debug("No record"); |
| return null; |
| } |
| } |
| } |
| |
| @Override |
| public int read() throws IOException { |
| byte[] b = new byte[1]; |
| if (read(b, 0, 1) != 1) { |
| return -1; |
| } else { |
| return b[0]; |
| } |
| } |
| |
| @Override |
| public int read(byte[] b, int off, int len) throws IOException { |
| int read = 0; |
| if (currentLogRecord == null) { |
| currentLogRecord = nextLogRecord(); |
| if (currentLogRecord == null) { |
| return read; |
| } |
| } |
| |
| while (read < len) { |
| int thisread = currentLogRecord.getPayLoadInputStream().read(b, off + read, (len - read)); |
| if (thisread == -1) { |
| currentLogRecord = nextLogRecord(); |
| if (currentLogRecord == null) { |
| return read; |
| } |
| } else { |
| LOG.debug("Offset saved = {}, persisted = {}", |
| currentPosition, currentLogRecord.getLogRecord().getTransactionId()); |
| currentPosition += thisread; |
| read += thisread; |
| } |
| } |
| return read; |
| } |
| |
| /** |
| * Position the reader at the given offset. If we fail to skip to the desired position |
| * and don't hit end of stream, return false. |
| * |
| * @throws org.apache.distributedlog.exceptions.EndOfStreamException if we attempt to |
| * skip past the end of the stream. |
| */ |
| public boolean skipTo(long position) throws IOException { |
| |
| // No need to skip anywhere. |
| if (position == position()) { |
| return true; |
| } |
| |
| LogReader skipReader = dlm.getInputStream(position); |
| LogRecordWithInputStream logRecord = null; |
| try { |
| logRecord = nextLogRecord(skipReader); |
| } catch (IOException ex) { |
| skipReader.close(); |
| throw ex; |
| } |
| |
| if (null == logRecord) { |
| return false; |
| } |
| |
| // We may end up with a reader positioned *before* the requested position if |
| // we're near the tail and the writer is still active, or if the desired position |
| // is not at a log record payload boundary. |
| // Transaction ID gives us the starting position of the log record. Read ahead |
| // if necessary. |
| currentPosition = logRecord.getOffset(); |
| currentLogRecord = logRecord; |
| LogReader oldReader = reader; |
| reader = skipReader; |
| |
| // Close the oldreader after swapping AppendOnlyStreamReader state. Close may fail |
| // and we need to make sure it leaves AppendOnlyStreamReader in a consistent state. |
| oldReader.close(); |
| |
| byte[] skipBuffer = new byte[SKIP_BUFFER_SIZE]; |
| while (currentPosition < position) { |
| long bytesToRead = Math.min(position - currentPosition, SKIP_BUFFER_SIZE); |
| long bytesRead = read(skipBuffer, 0, (int) bytesToRead); |
| if (bytesRead < bytesToRead) { |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| public long position() { |
| return currentPosition; |
| } |
| } |