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README.md

Hdfs file output plugin for Embulk

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A File Output Plugin for Embulk to write HDFS.

Overview

  • Plugin type: file output
  • Load all or nothing: yes
  • Resume supported: no
  • 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_prefix: prefix of target files (string, required)
  • file_ext: suffix of target files (string, required)
  • sequence_format: format for sequence part of target files (string, default: '%03d.%02d.')
  • rewind_seconds: When you use Date format in path_prefix property(like /tmp/embulk/%Y-%m-%d/out), the format is interpreted by using the time which is Now minus this property. (int, default: 0)
  • doas: username which access to Hdfs (string, default: executed user)
  • overwrite (Deprecated: Please use mode option instead): overwrite files when the same filenames already exists (boolean, default: false)
    • caution: even if this property is true, this does not mean ensuring the idempotence. if you want to ensure the idempotence, you need the procedures to remove output files after or before running.
  • delete_in_advance (Deprecated: Please use mode option instead): delete files and directories having path_prefix in advance (enum, default: NONE)
    • NONE: do nothing
    • FILE_ONLY: delete files
    • RECURSIVE: delete files and directories
  • mode: "abort_if_exist", "overwrite", "delete_files_in_advance", "delete_recursive_in_advance", or "replace". See below. (string, optional, default: "abort_if_exist")
    • In the future, default mode will become "replace".

CAUTION

If you use hadoop user (hdfs admin user) as doas, and if delete_in_advance is RECURSIVE, embulk-output-hdfs can delete any files and directories you indicate as path_prefix, this means embulk-output-hdfs can destroy your hdfs. So, please be careful when you use delete_in_advance option and doas option ...

About DELETE

When this plugin deletes files or directories, use Hadoop Trash API. So, you can find them in the trash during fs.trash.interval.

Modes

  • abort_if_exist:
    • Behavior: This mode writes rows to the target files in order. If target files already exist, abort the transaction.
    • Transactional: No. If fails, the target files could have some rows written.
    • Resumable: No.
  • overwrite:
    • Behavior: This mode writes rows to the target files in order. If target files already exist, this re-write from the beginning of the file.
    • Transactional: No. If fails, the target files could have some rows written.
    • Resumable: No.
  • delete_files_in_advance:
    • Behavior: This mode delete files at first, then writes rows to the target files in order.
    • Transactional: No. If fails, the target files could be removed.
    • Resumable: No.
  • delete_recursive_in_advance:
    • Behavior: This mode delete directories recursively at first, then writes rows to the target files in order.
    • Transactional: No. If fails, the target files could be removed.
    • Resumable: No.
  • replace:
    • Behavior: This mode writes rows to the workspace files in order, then replace them to target directories. This replace is not atomic because hdfs api does not have atomic replace.
    • Transactional: No. If fails, the target files could be removed.
    • Resumable: No.

Example

out:
  type: hdfs
  config_files:
    - /etc/hadoop/conf/core-site.xml
    - /etc/hadoop/conf/hdfs-site.xml
  config:
    fs.defaultFS: 'hdfs://hdp-nn1:8020'
    fs.hdfs.impl: 'org.apache.hadoop.hdfs.DistributedFileSystem'
    fs.file.impl: 'org.apache.hadoop.fs.LocalFileSystem'
  path_prefix: '/tmp/embulk/hdfs_output/%Y-%m-%d/out'
  file_ext: 'txt'
  overwrite: true
  formatter:
    type: csv
    encoding: UTF-8

Build

$ ./gradlew gem

Development

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

About

A File Output Plugin for Embulk to write HDFS.

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