org.apache.kafka.connect.util.ConnectorUtils Maven / Gradle / Ivy
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* 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.
*/
package org.apache.kafka.connect.util;
import java.util.ArrayList;
import java.util.List;
/**
* Utilities that connector implementations might find useful. Contains common building blocks
* for writing connectors.
*/
public class ConnectorUtils {
/**
* Given a list of elements and a target number of groups, generates list of groups of
* elements to match the target number of groups, spreading them evenly among the groups.
* This generates groups with contiguous elements, which results in intuitive ordering if
* your elements are also ordered (e.g. alphabetical lists of table names if you sort
* table names alphabetically to generate the raw partitions) or can result in efficient
* partitioning if elements are sorted according to some criteria that affects performance
* (e.g. topic partitions with the same leader).
*
* @param elements list of elements to partition
* @param numGroups the number of output groups to generate.
*/
public static List> groupPartitions(List elements, int numGroups) {
if (numGroups <= 0)
throw new IllegalArgumentException("Number of groups must be positive.");
List> result = new ArrayList<>(numGroups);
// Each group has either n+1 or n raw partitions
int perGroup = elements.size() / numGroups;
int leftover = elements.size() - (numGroups * perGroup);
int assigned = 0;
for (int group = 0; group < numGroups; group++) {
int numThisGroup = group < leftover ? perGroup + 1 : perGroup;
List groupList = new ArrayList<>(numThisGroup);
for (int i = 0; i < numThisGroup; i++) {
groupList.add(elements.get(assigned));
assigned++;
}
result.add(groupList);
}
return result;
}
}