Hdfs file input plugin for Embulk

Read files on Hdfs.

Overview

• Plugin type: file input
• Resume supported: not yet
• Cleanup supported: no

Configuration

• config_files list of paths to Hadoop's configuration files (array of strings, default: [])
• config overwrites configuration parameters (hash, default: {})
• path file path on Hdfs. you can use glob and Date format like %Y%m%d/%s.
• rewind_seconds When you use Date format in input_path property, the format is executed by using the time which is Now minus this property.
• partition when this is true, partition input files and increase task count. (default: true)
• num_partitions number of partitions. (default: Runtime.getRuntime().availableProcessors())

Example

in:
  type: hdfs
  config_files:
    - /opt/analytics/etc/hadoop/conf/core-site.xml
    - /opt/analytics/etc/hadoop/conf/hdfs-site.xml
  config:
    fs.defaultFS: 'hdfs://hadoop-nn1:8020'
    dfs.replication: 1
    fs.hdfs.impl: 'org.apache.hadoop.hdfs.DistributedFileSystem'
    fs.file.impl: 'org.apache.hadoop.fs.LocalFileSystem'
  path: /user/embulk/test/%Y-%m-%d/*
  rewind_seconds: 86400
  partition: true
  num_partitions: 30
  decoders:
    - {type: gzip}
  parser:
    charset: UTF-8
    newline: CRLF
    type: csv
    delimiter: "\t"
    quote: ''
    escape: ''
    trim_if_not_quoted: true
    skip_header_lines: 0
    allow_extra_columns: true
    allow_optional_columns: true
    columns:
    - {name: c0, type: string}
    - {name: c1, type: string}
    - {name: c2, type: string}
    - {name: c3, type: long}

Note

• The parameter num_partitions is the approximate value. The actual num_partitions is larger than this parameter.
  • see: The Partitioning Logic
• the feature of the partition supports only 3 line terminators.
  • \n
  • \r
  • \r\n

The Reference Implementation

• hito4t/embulk-input-filesplit

The Partitioning Logic

int partitionSizeByOneTask = totalFileLength / approximateNumPartitions;

/*
...
*/

    int numPartitions;
    if (path.toString().endsWith(".gz") || path.toString().endsWith(".bz2") || path.toString().endsWith(".lzo")) {
        // if the file is compressed, skip partitioning.
        numPartitions = 1;
    }
    else if (!task.getPartition()) {
        // if no partition mode, skip partitioning.
        numPartitions = 1;
    } 
    else {
        // equalize the file size per task as much as possible.
        numPartitions = ((fileLength - 1) / partitionSizeByOneTask) + 1;
    }

/*
...
*/

Build

$ ./gradlew gem

Development

$ ./gradlew classpath
$ bundle exec embulk run -I lib example.yml