Affects Version/s: 0.19.0
Fix Version/s: 0.20.0
With a 10 node cluster, there were only 9 online nodes. With about 215 total regions, each of the 9 had around 24 regions (average load is 24). Slop is 10% so 22 to 26 is the acceptable range.
Starting up the 10th node, master log showed:
The new regionserver received only 6 regions. This happened because when the 10th came in, average load dropped to 22. This caused two servers with 25 regions (acceptable when avg was 24 but not now) to reassign 3 of their regions each to bring them back down to the average. Unfortunately all other regions remained within the 10% slop (20 to 24) so they were not overloaded and thus did not reassign off any regions. It was only chance that made even 6 of the regions get reassigned as there could have been exactly 24 on each server, in which case none would have been assigned to the new node.
This will behave worse on larger clusters when adding a new node has little impact on the avg load/server.
|Refactor to Server Manager||Closed|