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https://issues.apache.org/jira/browse/IOTDB-460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17070677#comment-17070677
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WangChao commented on IOTDB-460:
--------------------------------
I think slot could has three info like following.
slot -> (state, source, destination)
state -> normal, rebalance
when a slot is rebalancing, it has following info.
slot -> (rebalance, source, destination)
when destination finished pulling the slot, it should start a raft log to chang
the slot state from rebalance to normal.
slot -> (normal, source, null)
source should check the slot's state, if slot is normal and source is not owned
by him, it could delete it.
So, we only support a change once time, like delete a node or add a node. Only
when all slots finished tranfer, we could do next change.
> [Distributed]Remove data of outdated slots
> ------------------------------------------
>
> Key: IOTDB-460
> URL: https://issues.apache.org/jira/browse/IOTDB-460
> Project: Apache IoTDB
> Issue Type: Improvement
> Reporter: Tian Jiang
> Priority: Major
> Labels: data-transfer, distributed
>
> In node addition/removal, the slots managed by a node will change. However,
> the data of corresponding slots cannot be removed yet because the new holders
> of the slots will pull such data to themselves. As the data pulling is issued
> by the new holders randomly, it is hard for the previous holders to find out
> when will the data be needless. As a result, the previous holder cannot
> delete the local data with confidence.
> It will be necessary to find a way for the previous holders to know when the
> data has been replicated to the new holders so that they will be able to
> remove the local data.
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