[HBASE-22306] Improve SLB to distribute table regions across all region servers

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Balancer
• Labels: balancer
• Assignee: Unassigned
• Reporter: Biju Nair
• Created: 24/Apr/19 22:48
• Updated: 25/Apr/19 01:01

Description

Noticed in clusters that distribution of regions of tables are skewed. From quick tests, it looks like that the current table skew cost may not be having any influence on selecting the target "cluster" candidate.

Cluster: 
Nodes  regions  Tables 
  5      50       5 

Test 1: Initial Distribution
———————————
Table 0 regions [1, 1, 2, 4, 2]
Table 1 regions [1, 2, 4, 2, 2]
Table 2 regions [0, 2, 2, 0, 4]
Table 3 regions [0, 5, 0, 2, 3]
Table 4 regions [0, 2, 4, 4, 1]

Test 1: After Balancer Run
———————————
Table 0 regions [2, 2, 2, 2, 2]
Table 1 regions [2, 2, 3, 2, 2]
Table 2 regions [1, 2, 2, 2, 1]
Table 3 regions [2, 3, 0, 2, 3]
Table 4 regions [3, 1, 3, 2, 2]

Test 2: Initial Distribution
———————————
Table 0 regions [2, 1, 0, 1, 2]
Table 1 regions [5, 1, 1, 2, 1]
Table 2 regions [2, 4, 0, 2, 4]
Table 3 regions [1, 4, 1, 3, 1]
Table 4 regions [2, 2, 0, 4, 4]

Test 2: After Balancer Run
———————————-
Table 0 regions [1, 2, 2, 1, 0]
Table 1 regions [2, 2, 2, 2, 2]
Table 2 regions [3, 3, 1, 2, 3]
Table 3 regions [2, 2, 2, 2, 2]
Table 4 regions [2, 1, 3, 3, 3]