org.apache.flink.streaming.runtime.partitioner.RescalePartitioner 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.streaming.runtime.partitioner;
import org.apache.flink.annotation.Internal;
import org.apache.flink.runtime.jobgraph.DistributionPattern;
import org.apache.flink.runtime.plugable.SerializationDelegate;
import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
/**
* Partitioner that distributes the data equally by cycling through the output
* channels. This distributes only to a subset of downstream nodes because
* {@link org.apache.flink.streaming.api.graph.StreamingJobGraphGenerator} instantiates
* a {@link DistributionPattern#POINTWISE} distribution pattern when encountering
* {@code SemiRebalancePartitioner}.
*
* The subset of downstream operations to which the upstream operation sends
* elements depends on the degree of parallelism of both the upstream and downstream operation.
* For example, if the upstream operation has parallelism 2 and the downstream operation
* has parallelism 4, then one upstream operation would distribute elements to two
* downstream operations while the other upstream operation would distribute to the other
* two downstream operations. If, on the other hand, the downstream operation has parallelism
* 2 while the upstream operation has parallelism 4 then two upstream operations will
* distribute to one downstream operation while the other two upstream operations will
* distribute to the other downstream operations.
*
*
In cases where the different parallelisms are not multiples of each other one or several
* downstream operations will have a differing number of inputs from upstream operations.
*
* @param Type of the elements in the Stream being rescaled
*/
@Internal
public class RescalePartitioner extends StreamPartitioner {
private static final long serialVersionUID = 1L;
private final int[] returnArray = new int[] {-1};
@Override
public int[] selectChannels(SerializationDelegate> record, int numberOfOutputChannels) {
int newChannel = ++this.returnArray[0];
if (newChannel >= numberOfOutputChannels) {
this.returnArray[0] = 0;
}
return this.returnArray;
}
public StreamPartitioner copy() {
return this;
}
@Override
public String toString() {
return "RESCALE";
}
}