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https://issues.apache.org/jira/browse/HELIX-674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16398867#comment-16398867
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ASF GitHub Bot commented on HELIX-674:
--------------------------------------

Github user mcvsubbu commented on a diff in the pull request:

    https://github.com/apache/helix/pull/145#discussion_r174526219
  
    --- Diff: 
helix-core/src/main/java/org/apache/helix/api/rebalancer/constraint/dataprovider/PartitionQuotaProvider.java
 ---
    @@ -0,0 +1,33 @@
    +package org.apache.helix.api.rebalancer.constraint.dataprovider;
    +
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *   http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing,
    + * software distributed under the License is distributed on an
    + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    + * KIND, either express or implied.  See the License for the
    + * specific language governing permissions and limitations
    + * under the License.
    + */
    +
    +/**
    + * An interface for getting partition quota information.
    + */
    +public interface PartitionQuotaProvider {
    +
    +  /**
    +   * @param resource
    +   * @param partition
    +   * @return The quota that is required by a certain partition in the 
specified resource
    +   */
    +  int getPartitionQuota(String resource, String partition);
    --- End diff --
    
    Clarify it with comments int he javadoc, with examples. I prefer weight 
rather than quota
    
    A specific example class with a lot of javadocs on different scenarios and 
how these classes are to be used, will not hurt. Tests can serve as examples, 
but they are usually sloppy, and if they are examples, then they tend to be 
copy-pasted the same way in real code.


> Constraint Based Resource Rebalancer
> ------------------------------------
>
>                 Key: HELIX-674
>                 URL: https://issues.apache.org/jira/browse/HELIX-674
>             Project: Apache Helix
>          Issue Type: New Feature
>            Reporter: Jiajun Wang
>            Assignee: Jiajun Wang
>            Priority: Major
>             Fix For: 0.8.x
>
>         Attachments: Constraint-BasedResourceRebalancing-080318-2226-240.pdf
>
>
> Helix rebalancer assigns resources according to different strategies. 
> Recently, we optimize the strategy for evenness and minimize movement. 
> However, the evenness here only applies to partition numbers. Moreover, we've 
> got more requests for customizable rebalancer from our users.
> Take partition weight as an example:
> In reality, partition replicas have different size. We use "partition weight" 
> as an abstraction of the partition size. It can be network traffic usage, 
> disk usage, or any other combined factors.
> Given each partition may have different weights, Helix should be able to 
> assign partition accordingly. So that the distribution would be even 
> regarding the weight.
> In this project, we are planning new rebalancer mechanism that generates 
> resource partition assignment according to a list of "constraints". Current 
> rebalance strategy can be regarded as one kind of constraint. Moving forward, 
> Helix users would be able to extend the constraint interface using their own 
> logic.
> Some init discussions are in progress and we will have a proposal posted here 
> soon.



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