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From tweise <...@git.apache.org>
Subject [GitHub] incubator-apex-malhar pull request: APEXMALHAR-1965 WAL Utility
Date Fri, 22 Apr 2016 01:07:17 GMT
Github user tweise commented on a diff in the pull request:

    https://github.com/apache/incubator-apex-malhar/pull/242#discussion_r60678798
  
    --- Diff: library/src/main/java/org/apache/apex/malhar/lib/wal/FileSystemWAL.java ---
    @@ -0,0 +1,688 @@
    +/**
    + * 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.apex.malhar.lib.wal;
    +
    +import java.io.DataInputStream;
    +import java.io.DataOutputStream;
    +import java.io.IOException;
    +import java.util.EnumSet;
    +import java.util.HashSet;
    +import java.util.Iterator;
    +import java.util.Map;
    +import java.util.Set;
    +import java.util.TreeMap;
    +
    +import javax.validation.constraints.Min;
    +import javax.validation.constraints.NotNull;
    +
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import org.apache.apex.malhar.lib.utils.FileContextUtils;
    +import org.apache.apex.malhar.lib.utils.IOUtils;
    +import org.apache.hadoop.fs.CreateFlag;
    +import org.apache.hadoop.fs.FileContext;
    +import org.apache.hadoop.fs.FileStatus;
    +import org.apache.hadoop.fs.Options;
    +import org.apache.hadoop.fs.Path;
    +import org.apache.hadoop.fs.RemoteIterator;
    +import org.apache.hadoop.fs.Syncable;
    +import org.apache.hadoop.fs.local.LocalFs;
    +import org.apache.hadoop.fs.local.RawLocalFs;
    +
    +import com.google.common.base.Preconditions;
    +
    +import com.datatorrent.api.annotation.Stateless;
    +import com.datatorrent.netlet.util.Slice;
    +
    +/**
    + * A WAL implementation that is file based.
    + * <p/>
    + * Note:<br/>
    + * The FileSystem Writer and Reader operations should not alternate because intermingling
these operations will cause
    + * problems. Typically the  WAL Reader will only used in recovery.<br/>
    + *
    + * Also this implementation is thread unsafe- the filesystem wal writer and reader operations
should be performed in
    + * operator's thread.
    + */
    +public class FileSystemWAL implements WAL<FileSystemWAL.FileSystemWALReader, FileSystemWAL.FileSystemWALWriter>
    +{
    +
    +  @NotNull
    +  private String filePath;
    +
    +  //max length of the file
    +  @Min(0)
    +  private long maxLength;
    +
    +  private FileSystemWALPointer walStartPointer = new FileSystemWALPointer(0, 0);
    +
    +  @NotNull
    +  private FileSystemWAL.FileSystemWALReader fileSystemWALReader = new FileSystemWALReader(this);
    +
    +  @NotNull
    +  private FileSystemWAL.FileSystemWALWriter fileSystemWALWriter = new FileSystemWALWriter(this);
    +
    +  //part => tmp file path;
    +  private final Map<Integer, String> tempPartFiles = new TreeMap<>();
    +
    +  private long lastCheckpointedWindow = Stateless.WINDOW_ID;
    +
    +  @Override
    +  public void setup()
    +  {
    +    try {
    +      FileContext fileContext = FileContextUtils.getFileContext(filePath);
    +      if (maxLength == 0) {
    +        maxLength = fileContext.getDefaultFileSystem().getServerDefaults().getBlockSize();
    +      }
    +      fileSystemWALWriter.open(fileContext);
    +      fileSystemWALReader.open(fileContext);
    +    } catch (IOException e) {
    +      throw new RuntimeException("during setup", e);
    +    }
    +  }
    +
    +  @Override
    +  public void beforeCheckpoint(long window)
    +  {
    +    try {
    +      lastCheckpointedWindow = window;
    +      fileSystemWALWriter.flush();
    +    } catch (IOException e) {
    +      throw new RuntimeException("during before cp", e);
    +    }
    +  }
    +
    +  @Override
    +  public void committed(long window)
    --- End diff --
    
    Why does it happen in committed. Shouldn't the file be renamed as soon as it is closed?



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