Github user mcvsubbu commented on a diff in the pull request:
https://github.com/apache/helix/pull/145#discussion_r176490613
--- Diff:
helix-core/src/main/java/org/apache/helix/api/rebalancer/constraint/dataprovider/CapacityProvider.java
---
@@ -0,0 +1,48 @@
+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.
+ * The return value will be used to estimate available capacity, as well
as utilization in percentage for prioritizing participants.
+ *
+ * Note that all return values of the provider are supposed to be in the
same unit.
+ * For example, if the provider is for memory capacity of a host (total
memory size is 8G, current usage is 512MB),
+ * the return values could be {@link
org.apache.helix.api.rebalancer.constraint.dataprovider.CapacityProvider#getParticipantCapacity(String)}
= 8192, and {@link
org.apache.helix.api.rebalancer.constraint.dataprovider.CapacityProvider#getParticipantUsage(String)}
= 512.
+ * Another example, if the provider is for partition count capacity (max
count 1000 partitions, currently no partition assigned),
+ * the return values should be {@link
org.apache.helix.api.rebalancer.constraint.dataprovider.CapacityProvider#getParticipantCapacity(String)}
= 1000, and {@link
org.apache.helix.api.rebalancer.constraint.dataprovider.CapacityProvider#getParticipantUsage(String)}
= 0.
+ *
+ * Moreover, while this provider is used together with a {@link
org.apache.helix.api.rebalancer.constraint.dataprovider.PartitionWeightProvider
PartitionWeightProvider},
+ * both providers are supposed to return values in the same unit so they
can be used to estimate the resource usage of an proposed assignment.
+ */
+public interface CapacityProvider {
+
+ /**
+ * @param participant
+ * @return The total participant capacity.
+ */
+ int getParticipantCapacity(String participant);
+
+ /**
+ * @param participant
+ * @return The participant usage (provisioned capacity).
--- End diff --
The comment "(provisioned capacity)" is confusing. Can we remove it?
---
