[HDFS-1448] Create multi-format parser for edits logs file, support binary and XML formats initially

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.22.0
• Fix Version/s: 0.23.0
• Component/s: tools
• Hadoop Flags: Reviewed

Release Note

Offline edits viewer feature adds oev tool to hdfs script. Oev makes it possible to convert edits logs to/from native binary and XML formats. It uses the same framework as Offline image viewer.

Example usage:

$HADOOP_HOME/bin/hdfs oev -i edits -o output.xml

• Assignee: Erik Steffl
• Reporter: Erik Steffl
• Created: 08/Oct/10 22:47
• Updated: 17/Feb/12 23:25
• Resolved: 21/Jan/11 22:22

Description

Create multi-format parser for edits logs file, support binary and XML formats initially.

Parsing should work from any supported format to any other supported format (e.g. from binary to XML and from XML to binary).

The binary format is the format used by FSEditLog class to read/write edits file.

Primary reason to develop this tool is to help with troubleshooting, the binary format is hard to read and edit (for human troubleshooters).

Longer term it could be used to clean up and minimize parsers for fsimage and edits files. Edits parser OfflineEditsViewer is written in a very similar fashion to OfflineImageViewer. Next step would be to merge OfflineImageViewer and OfflineEditsViewer and use the result in both FSImage and FSEditLog. This is subject to change, specifically depending on adoption of avro (which would completely change how objects are serialized as well as provide ways to convert files to different formats).

Issue Links

• is duplicated by: HDFS-209 Provide tool to view/change edits file
• is duplicated by: HDFS-312 FSEditLog dump/restore tool
• is related to: HDFS-842 Serialize NN edits log as avro records