[jira] [Updated] (HELIX-654) Rebalance running task

["Weihan Kong (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HELIX-654?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Weihan Kong updated HELIX-654:
------------------------------
    Description: 
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.

  was:Currently, for generic tasks, running task won't be rebalanced if cluster topology changes. This feature enable user to specify, on the job level, whether the task framework should drop the running task and re-assign it to the new node when cluster topology changes(and "ideal" assignment changes).


> 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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