[CASSANDRA-762] Load balancing does not account for the load of the moving node

• Type: Bug
• Status: Resolved
• Priority: Low
• Resolution: Fixed
• Fix Version/s: 0.5
• Severity: Low
• Assignee: Stu Hood
• Reporter: Stu Hood

Authors

Stu Hood

• Created: 03/Feb/10 23:20
• Updated: 16/Apr/19 09:33
• Resolved: 10/Feb/10 02:15

Description

Given a node A (with load 10 gb) and a node B (with load 20 gb), running the loadbalance command against node A will:
1. Remove node A from the ring

• Recalculates pending ranges so that node B is responsible for the entire ring
  2. Pick the most loaded node
• node B is still reporting 20 gb load, because that is all it has locally
  3. Choose a token that divides the range of the most loaded node in half

Since the token calculation doesn't take into account the load that node B is 'inheriting' from node A, the token will divide node B's load in half and swap the loads. Instead, the token calculation needs to pretend that B has already inherited the 10 gb from node A, for a total of 30 gb. The token that should be chosen falls at 15 gb of the total load, or 5 gb into node B's load.