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https://issues.apache.org/jira/browse/HELIX-674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16406750#comment-16406750
 ] 

ASF GitHub Bot commented on HELIX-674:
--------------------------------------

Github user lei-xia commented on a diff in the pull request:

    https://github.com/apache/helix/pull/145#discussion_r175858026
  
    --- Diff: 
helix-core/src/main/java/org/apache/helix/controller/rebalancer/constraint/TotalCapacityConstraint.java
 ---
    @@ -0,0 +1,79 @@
    +package org.apache.helix.controller.rebalancer.constraint;
    +
    +/*
    + * 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.
    + */
    +
    +import 
org.apache.helix.api.rebalancer.constraint.AbstractRebalanceHardConstraint;
    +import 
org.apache.helix.api.rebalancer.constraint.dataprovider.CapacityProvider;
    +import 
org.apache.helix.api.rebalancer.constraint.dataprovider.PartitionWeightProvider;
    +import org.apache.helix.controller.common.ResourcesStateMap;
    +import org.apache.helix.controller.rebalancer.util.ResourceUsageCalculator;
    +
    +import java.util.HashMap;
    +import java.util.Map;
    +
    +public class TotalCapacityConstraint extends 
AbstractRebalanceHardConstraint {
    +  private final PartitionWeightProvider _partitionWeightProvider;
    +  private final CapacityProvider _capacityProvider;
    +  // Use to track any assignments that are proposed during the rebalance 
process.
    +  // Note these assignments are not reflected in providers.
    +  private final Map<String, Integer> _pendingUsage;
    +
    +  public TotalCapacityConstraint(PartitionWeightProvider 
partitionWeightProvider,
    +      CapacityProvider capacityProvider) {
    +    super();
    +    _partitionWeightProvider = partitionWeightProvider;
    +    _capacityProvider = capacityProvider;
    +    _pendingUsage = new HashMap<>();
    +  }
    +
    +  private boolean validate(String resource, String partition, String 
participant) {
    +    int usage = _capacityProvider.getParticipantUsage(participant) + 
(_pendingUsage
    +        .containsKey(participant) ? _pendingUsage.get(participant) : 0);
    +    return +_partitionWeightProvider.getPartitionWeight(resource, 
partition) + usage
    --- End diff --
    
    why there is a "+" in begining of the statement?


> 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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