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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (APEXMALHAR-2116) File Record reader module
Date Thu, 21 Jul 2016 12:48:20 GMT

    [ https://issues.apache.org/jira/browse/APEXMALHAR-2116?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15387621#comment-15387621
] 

ASF GitHub Bot commented on APEXMALHAR-2116:
--------------------------------------------

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

    https://github.com/apache/apex-malhar/pull/326#discussion_r71698302
  
    --- Diff: library/src/main/java/org/apache/apex/malhar/lib/fs/FSRecordReaderModule.java
---
    @@ -0,0 +1,344 @@
    +/**
    + * 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.fs;
    +
    +import javax.validation.constraints.Min;
    +
    +import javax.validation.constraints.NotNull;
    +import javax.validation.constraints.Size;
    +
    +import org.apache.apex.malhar.lib.fs.FSRecordReader.RECORD_READER_MODE;
    +import org.apache.hadoop.conf.Configuration;
    +
    +import com.datatorrent.api.Context;
    +import com.datatorrent.api.DAG;
    +import com.datatorrent.api.Module;
    +import com.datatorrent.common.partitioner.StatelessPartitioner;
    +import com.datatorrent.lib.codec.KryoSerializableStreamCodec;
    +import com.datatorrent.lib.io.block.BlockMetadata;
    +import com.datatorrent.lib.io.block.FSSliceReader;
    +import com.datatorrent.lib.io.fs.FileSplitterInput;
    +
    +/**
    + * This module is used for reading records/tuples from FileSystem. Records can
    + * be read in parallel using multiple partitions of record reader operator.
    + * (Ordering is not guaranteed when records are read in parallel)
    + *
    + * Input directory is scanned at specified interval to poll for new data.
    + * 
    + * The module reads data in parallel, following parameters can be configured
    + * <br/>
    + * 1. files: list of file(s)/directories to read<br/>
    + * 2. filePatternRegularExp: Files with names matching given regex will be read<br/>
    + * 3. scanIntervalMillis: interval between two scans to discover new files in
    + * input directory<br/>
    + * 4. recursive: if true, scan input directories recursively<br/>
    + * 5. blockSize: block size used to read input blocks of file<br/>
    + * 6. readersCount: count of readers to read input file<br/>
    + * 7. sequentialFileRead: if true, then each reader partition will read different file.
<br/>
    + *    instead of reading different offsets of the same file. <br/>
    + *    (File level parallelism instead of block level parallelism)<br/>
    + * 8. blocksThreshold: number of blocks emitted per window
    + */
    +@org.apache.hadoop.classification.InterfaceStability.Evolving
    +public class FSRecordReaderModule implements Module
    +{
    +  @NotNull
    +  @Size(min = 1)
    +  private String files;
    +  private String filePatternRegularExp;
    +  @Min(1)
    +  private long scanIntervalMillis = 5000;
    +  private boolean recursive = true;
    +  private boolean sequentialFileRead = false;
    +  @Min(1)
    +  private int readersCount = 1;
    +  @Min(1)
    +  protected int blocksThreshold = 1;
    +
    +  public final transient ProxyOutputPort<byte[]> records = new ProxyOutputPort<byte[]>();
    +
    +  /**
    +   * Criteria for record split
    +   */
    +  private RECORD_READER_MODE mode = RECORD_READER_MODE.DELIMITED_RECORD;
    +
    +  /**
    +   * Length for fixed width record
    +   */
    +  @Min(1)
    +  private int recordLength;
    --- End diff --
    
    @amberarrow As per your suggestion, removed @ min annotation for record length.
    Added validation in the code to ensure that the value is positive if FIXED_WIDTH_RECORD.
    Also, added test case for validating this.
    
    Could you have a look and merge this if it looks OK.


> File Record reader module
> -------------------------
>
>                 Key: APEXMALHAR-2116
>                 URL: https://issues.apache.org/jira/browse/APEXMALHAR-2116
>             Project: Apache Apex Malhar
>          Issue Type: New Feature
>            Reporter: Yogi Devendra
>            Assignee: Yogi Devendra
>
> This will be useful for the usecases which involves reading from files "line by line"
in parallel and emit each line as seperate tuple.
> Proposal is to have new Module which would allow users to monitor directories, read files
and emit data records(tuple). Records are based on record separator (e.g. newline) or fixed
size (no of bytes). 
> Plan is as follows:
> 1. New operator FileRecordReader which will extend BlockReader.
> 2. This operator will have configuration option to select mode for FIXED_LENGTH, SEPARATOR_BASED
recors. 
> 3. Using appropriate ReaderContext based on mode.
> 4. New module FileRecordReaderModule which wraps (FileSplitter (existing) + FileRecordReader
operator)
> Reason for having different operator than BlockReader is because output port signature
is different than BlockReader.
>  



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