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Posted to commits@cassandra.apache.org by "Jonathan Ellis (JIRA)" <ji...@apache.org> on 2010/02/08 17:12:28 UTC
[jira] Commented: (CASSANDRA-762) Load balancing does not account
for the load of the moving node
[ https://issues.apache.org/jira/browse/CASSANDRA-762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12830991#action_12830991 ]
Jonathan Ellis commented on CASSANDRA-762:
------------------------------------------
did you test on 0.5?
> Load balancing does not account for the load of the moving node
> ---------------------------------------------------------------
>
> Key: CASSANDRA-762
> URL: https://issues.apache.org/jira/browse/CASSANDRA-762
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 0.5, 0.6
> Reporter: Stu Hood
> Assignee: Stu Hood
> Priority: Minor
> Fix For: 0.5, 0.6
>
> Attachments: 0001-Wait-BROADCAST_INTERVAL-for-load-information-and-cal.patch, for-0.5-0001-Wait-BROADCAST_INTERVAL-for-load-information-and-cal.patch
>
>
> 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.
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