modules/compute/src/jobs/java/org/apache/ignite/internal/compute/MapReduce.java

/*
 * 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.ignite.internal.compute;

import static java.util.stream.Collectors.toList;

import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import org.apache.ignite.compute.DeploymentUnit;
import org.apache.ignite.compute.JobExecutionOptions;
import org.apache.ignite.compute.task.ComputeJobRunner;
import org.apache.ignite.compute.task.MapReduceTask;
import org.apache.ignite.compute.task.TaskExecutionContext;

/** Map reduce task which runs a {@link GetNodeNameJob} on each node and computes a sum of length of all node names. */
public class MapReduce implements MapReduceTask<Integer> {
    @Override
    public List<ComputeJobRunner> split(TaskExecutionContext taskContext, Object... args) {
        List<DeploymentUnit> deploymentUnits = (List<DeploymentUnit>) args[0];

        return taskContext.ignite().clusterNodes().stream().map(node ->
                ComputeJobRunner.builder()
                        .jobClassName(GetNodeNameJob.class.getName())
                        .units(deploymentUnits)
                        .nodes(Set.of(node))
                        .options(JobExecutionOptions.builder()
                                .maxRetries(10)
                                .priority(Integer.MAX_VALUE)
                                .build()
                        ).build()
        ).collect(toList());
    }

    @Override
    public Integer reduce(Map<UUID, ?> results) {
        return results.values().stream()
                .map(String.class::cast)
                .map(String::length)
                .reduce(Integer::sum)
                .orElseThrow();
    }
}