[HBASE-28204] Region Canary can take lot more time If any region (except the first region) starts with delete markers

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.6.0, 2.4.18, 2.5.8, 3.0.0-beta-2
• Component/s: canary
• Labels: pull-request-available
• Hadoop Flags: Reviewed

Release Note

Canary is using Scan for first region of the table and Get for rest of the region. RAW Scan was only enabled for first region of any table. If a region has high number of deleted rows for the first row of the key-space, then It can take really long time for Get to finish execution.

With this change, Region canary will use scan to validate that every region is accessible and also enables RAW Scan if it's enabled by the user.

• Assignee: Mihir Monani
• Reporter: Mihir Monani
• Created: 14/Nov/23 23:34
• Updated: 13/Feb/24 20:21
• Resolved: 12/Feb/24 17:17

Description

In CanaryTool.java, Canary reads only the first row of the region using Get for any region of the table. Canary uses Scan with FirstRowKeyFilter for table scan If the said region has empty start key (This will only happen when region is the first region for a table)

With HBASE-16091 RawScan was implemented to improve performance for regions which can have high number of delete markers. Based on currently implementation, RawScan is only enabled if region has empty start-key (or region is first region for the table).

RawScan doesn't work for rest of the regions in the table except first region. Also If the region has all the rows or majority of the rows with delete markers, Get Operation can take a lot of time. This is can cause timeouts for CanaryTool.

Issue Links

• is related to: HBASE-28356 RegionServer Canary can should use Scan just like Region Canary with option to enable Raw Scan
• relates to: HBASE-16091 Canary takes lot more time when there are delete markers in the table
• links to: GitHub Pull Request #5522
• links to: GitHub Pull Request #5675