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https://issues.apache.org/jira/browse/HELIX-674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16398864#comment-16398864
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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_r174525270
--- Diff:
helix-core/src/main/java/org/apache/helix/api/rebalancer/constraint/dataprovider/CapacityProvider.java
---
@@ -0,0 +1,38 @@
+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 participant capacity information.
+ */
+public interface CapacityProvider {
+
+ /**
+ * @param participant
+ * @return The total participant capacity.
+ */
+ int getParticipantCapacity(String participant);
+
+ /**
+ * @param participant
+ * @return The provisioned capacity.
+ */
+ int getParticipantProvisioned(String participant);
--- End diff --
Please provide examples in the javadoc. In this case, I would add something
like: "For example if the constraint is on memory used by a resource in a
participant, and the participant is provisioned with a max of 10MB for
resources, out of which 40k is used, the getParticpantUsage() should return 40,
and getParticipantCapacity() should return 100000. On the other hand, if the
constraint is on number of partitions in a participant, and the particpant has
been provisioned to for a max of 1200 partitions, but has only 65, then
getParticipantUsage() should return 65, and getParticipantCapacity() should
return 1200" -- something like this. It does not hurt to have more comments.
You will get less questions.
> 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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