[HADOOP-18596] Distcp -update between different cloud stores to use modification time while checking for file skip.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.6
• Component/s: tools/distcp
• Labels: pull-request-available
• Target Version/s: 3.3.9
• Assignee: Mehakmeet Singh
• Reporter: Mehakmeet Singh
• Created: 17/Jan/23 05:51
• Updated: 22/Jun/23 20:30
• Resolved: 15/Feb/23 11:22

Description

Distcp -update currently relies on File size, block size, and Checksum comparisons to figure out which files should be skipped or copied.
Since different cloud stores have different checksum algorithms we should check for modification time as well to the checks.

This would ensure that while performing -update if the files are perceived to be out of sync we should copy them. The machines between which the file transfers occur should be in time sync to avoid any extra copies.

Improving testing and documentation for modification time checks between different object stores to ensure no incorrect skipping of files.

Issue Links

• causes: HADOOP-18633 fix test AbstractContractDistCpTest#testDistCpUpdateCheckFileSkip
• links to: GitHub Pull Request #5308
• links to: GitHub Pull Request #5387