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,
* 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.flink.streaming.runtime.partitioner;
import org.apache.flink.annotation.Internal;
import org.apache.flink.runtime.io.network.api.writer.SubtaskStateMapper;
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 RescalePartitioner}.
*
* 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 int nextChannelToSendTo = -1;
@Override
public int selectChannel(SerializationDelegate> record) {
if (++nextChannelToSendTo >= numberOfChannels) {
nextChannelToSendTo = 0;
}
return nextChannelToSendTo;
}
@Override
public SubtaskStateMapper getDownstreamSubtaskStateMapper() {
return SubtaskStateMapper.UNSUPPORTED;
}
@Override
public SubtaskStateMapper getUpstreamSubtaskStateMapper() {
return SubtaskStateMapper.UNSUPPORTED;
}
public StreamPartitioner copy() {
return this;
}
@Override
public String toString() {
return "RESCALE";
}
@Override
public boolean isPointwise() {
return true;
}
}