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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (APEXMALHAR-1965) Create a WAL in Malhar
Date Tue, 29 Mar 2016 21:11:25 GMT

    [ https://issues.apache.org/jira/browse/APEXMALHAR-1965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15216843#comment-15216843
] 

ASF GitHub Bot commented on APEXMALHAR-1965:
--------------------------------------------

Github user ishark commented on a diff in the pull request:

    https://github.com/apache/incubator-apex-malhar/pull/204#discussion_r57801373
  
    --- Diff: library/src/main/java/org/apache/apex/malhar/lib/wal/FSWal.java ---
    @@ -0,0 +1,178 @@
    +/**
    + * 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.EOFException;
    +import java.io.IOException;
    +
    +import org.apache.hadoop.fs.FSDataOutputStream;
    +
    +import com.google.common.base.Preconditions;
    +
    +import com.datatorrent.lib.fileaccess.FileAccess;
    +
    +/**
    + * WAL implementation which allows writing entries to single file.
    + * the pointer type is the offset in the file. The entry is serialized into byte array
and
    + * first length of the entry is written followed by the serialized bytes.
    + * @param <T>
    + */
    +public class FSWal<T> implements WAL<T, Long>
    +{
    +  transient long bucketKey;
    +  private transient String name;
    +  private transient FileAccess fa;
    +  private transient WAL.Serde<T> serde;
    +
    +  public FSWal(FileAccess fa, WAL.Serde<T> serde, long bucketKey, String name)
    --- End diff --
    
    Does it make sense to have WAL with simple File APIs instead of FileAccess? That would
make it generic to use. Also, can bucketKey be a string instead of long?


> Create a WAL in Malhar
> ----------------------
>
>                 Key: APEXMALHAR-1965
>                 URL: https://issues.apache.org/jira/browse/APEXMALHAR-1965
>             Project: Apache Apex Malhar
>          Issue Type: Task
>            Reporter: Chandni Singh
>            Assignee: Tushar Gosavi
>
> In Malhar we have an IdempotentStorageManager which we use like a Write Ahead Logger.
There have been some other places where we have created a different flavor of Write Ahead
Logger. 
> We need to find overlap between all these flavors and create a common Write Ahead Logger
for use in Apex core and Apex malhar.



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