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https://issues.apache.org/jira/browse/HELIX-654?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16086664#comment-16086664
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ASF GitHub Bot commented on HELIX-654:
--------------------------------------
Github user asfgit closed the pull request at:
https://github.com/apache/helix/pull/88
> Rebalance running task
> ----------------------
>
> Key: HELIX-654
> URL: https://issues.apache.org/jira/browse/HELIX-654
> Project: Apache Helix
> Issue Type: New Feature
> Components: helix-core
> Reporter: Weihan Kong
>
> h3. Feature summary
> Helix Task Framework empowers user to run tasks on instances managed by
> Helix. There're 2 type of tasks: generic task and fixed target task. For
> fixed target task, the task always follows the targeted partition and is
> rebalanced if the partition is rebalanced. For generic task, Helix provides
> user the choice to rebalance the running task or not, when the topology of
> the cluster changes.
> For most users, it's better to disabled this feature(as default) since
> there's no need to re-run the task every time new node is added. For users
> with long-running tasks, enabling this feature can be very useful so that
> when new node is added, the load of the tasks are better balanced among the
> cluster.
> h3. Defined system behavior
> h4. When a node fails,
> h6. Feature disabled:
> * Running tasks on that failed node will be rebalanced to a live node, since
> the task no longer exists and failed with the node.
> h6. Feature enabled:
> * Same.
> h4. When a new node is added,
> h6. Feature disabled:
> * Running tasks will continue to run on the current instance.
> * If a running task fails after a while, it might be rebalanced and run on
> other instances, according to the new rebalance assignment under the new
> cluster topology.
> h6. Feature enabled:
> * Running task might be cancelled and rebalanced immediately, according to
> the new rebalance assignment under the new cluster topology.
> h3. Configuration
> A job level config field(RebalanceRunningTask) in JobConfig to enable/disable
> this feature. By default it's false.
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