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From Changgeng Li <li.changg...@gmail.com>
Subject Re: Customized rebalancer
Date Thu, 25 Jun 2015 06:13:38 GMT
yes, it's always null.

actually I checked the code that parameter was never set.
https://github.com/apache/helix/blob/acd902e2433f65e9864ccf49fcd1a04c36b1f206/helix-core/src/main/java/org/apache/helix/controller/stages/BestPossibleStateCalcStage.java#L222

On Wed, Jun 24, 2015 at 10:41 PM, kishore g <g.kishore@gmail.com> wrote:

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> ---------- Forwarded message ----------
> From: kishore g <g.kishore@gmail.com>
> Date: Wed, Jun 24, 2015 at 10:37 PM
> Subject: Re: Customized rebalancer
> To: "user@helix.apache.org" <user@helix.apache.org>
>
>
> Hi Changgeng,
>
> I think the first invocation will always be null, subsequent invocations
> should provide you the previous resource assignment. Are you saying its
> always null?.
>
> thanks,
> Kishore G
>
> On Wed, Jun 24, 2015 at 3:42 PM, Changgeng Li <li.changgeng@gmail.com>
> wrote:
>
>> Hello,
>>
>> We have a use case that when adding or removing a new node, we hope to
>> minimize the shuffle of partitions between nodes. I'm trying to implement a
>> customized rebalancer calculating the new resource assignment based on the
>> previous resource assignment. When a new node is added, just move some
>> partitions from existing node to the new node, and when a node is down,
>> move the partitions on this node to the other nodes. Partitions would not
>> move between two nodes if the both status are not changed.
>>
>> The documentation says:
>> In rebalance(), ... the third is the output of the previous invocation
>> of this method (if supported) ...
>>
>> During my testing I found the previous resource assignment passed in is
>> always null. my question is what "if supported" means here? Does the
>> rebalancer need to support something?
>>
>>
>> Any other suggestions are also welcome.
>>
>> Thanks,
>> Changgeng
>>
>
>
>

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