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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HELIX-674) Constraint Based Resource Rebalancer
Date Wed, 14 Mar 2018 00:41:00 GMT

    [ https://issues.apache.org/jira/browse/HELIX-674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16397911#comment-16397911
] 

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

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

    https://github.com/apache/helix/pull/145#discussion_r174326343
  
    --- Diff: helix-core/src/main/java/org/apache/helix/util/WeightAwareRebalanceUtil.java
---
    @@ -0,0 +1,141 @@
    +package org.apache.helix.util;
    +
    +import org.apache.helix.HelixException;
    +import org.apache.helix.ZNRecord;
    +import org.apache.helix.api.config.RebalanceConfig;
    +import org.apache.helix.api.rebalancer.constraint.AbstractRebalanceHardConstraint;
    +import org.apache.helix.api.rebalancer.constraint.AbstractRebalanceSoftConstraint;
    +import org.apache.helix.controller.common.PartitionStateMap;
    +import org.apache.helix.controller.common.ResourcesStateMap;
    +import org.apache.helix.controller.rebalancer.strategy.ConstraintRebalanceStrategy;
    +import org.apache.helix.controller.stages.ClusterDataCache;
    +import org.apache.helix.model.*;
    +
    +import java.util.ArrayList;
    +import java.util.HashMap;
    +import java.util.List;
    +import java.util.Map;
    +
    +/**
    + * A rebalance tool that generate an resource partition assignment based on the input.
    + * Note the assignment won't be automatically applied to the cluster. Applications are
supposed to
    + * apply the change.
    + */
    +public class WeightAwareRebalanceUtil {
    +  private final ClusterConfig _clusterConfig;
    +  private final Map<String, InstanceConfig> _instanceConfigMap = new HashMap<>();
    +  // For the possible customized state models.
    +  private final Map<String, StateModelDefinition> _stateModelDefs = new HashMap<>();
    +  private final ClusterDataCache _dataCache;
    +
    +  public enum RebalanceOption {
    +    INIT,
    +    REASSIGN
    +  }
    +
    +  public WeightAwareRebalanceUtil(ClusterConfig clusterConfig,
    +      List<InstanceConfig> instanceConfigs) {
    +    for (InstanceConfig instanceConfig : instanceConfigs) {
    +      _instanceConfigMap.put(instanceConfig.getInstanceName(), instanceConfig);
    +    }
    +    _clusterConfig = clusterConfig;
    +
    +    _dataCache = new ClusterDataCache();
    +    _dataCache.setInstanceConfigMap(_instanceConfigMap);
    +    _dataCache.setClusterConfig(_clusterConfig);
    +    List<LiveInstance> liveInstanceList = new ArrayList<>();
    +    for (String instance : _instanceConfigMap.keySet()) {
    +      LiveInstance liveInstance = new LiveInstance(instance);
    +      liveInstanceList.add(liveInstance);
    +    }
    +    _dataCache.setLiveInstances(liveInstanceList);
    +  }
    +
    +  /**
    +   * The method to generate partition assignment mappings.
    +   *
    +   * @param resourceConfigs    Config of all the resources that need to be rebalanced.
    +   *                           The tool throws Exception if any resource has no IS or
broken/uninitialized IS.
    +   *                           The tool throws Exception if any resource is in full-auto
mode.
    +   * @param existingAssignment The existing partition assignment of the input resources.
    +   * @param option             INIT or REASSIGN
    +   *                           INIT: Keep existing assignment. Only generate new partition
assignment.
    --- End diff --
    
    "Mode" is confusing while we already have "RebalanceMode".
    
    About the option name, how about "incremental" rebalance & "full" rebalance? I think
those 2 names are much better.
    
    I will add the comment about the resourceConfig, this is where users should specify the
partitions.
    Also, as a standalone tool, most rebalance options won't work even configured in the cluster
config / instance config. I will add comments to point it out.


> 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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