CapBasedLoadManager.java
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上传日期:2018-01-08
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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.hadoop.mapred;
- /**
- * A {@link LoadManager} for use by the {@link FairScheduler} that allocates
- * tasks evenly across nodes up to their per-node maximum, using the default
- * load management algorithm in Hadoop.
- */
- public class CapBasedLoadManager extends LoadManager {
- /**
- * Determine how many tasks of a given type we want to run on a TaskTracker.
- * This cap is chosen based on how many tasks of that type are outstanding in
- * total, so that when the cluster is used below capacity, tasks are spread
- * out uniformly across the nodes rather than being clumped up on whichever
- * machines sent out heartbeats earliest.
- */
- int getCap(int totalRunnableTasks, int localMaxTasks, int totalSlots) {
- double load = ((double)totalRunnableTasks) / totalSlots;
- return (int) Math.ceil(localMaxTasks * Math.min(1.0, load));
- }
- @Override
- public boolean canAssignMap(TaskTrackerStatus tracker,
- int totalRunnableMaps, int totalMapSlots) {
- return tracker.countMapTasks() < getCap(totalRunnableMaps,
- tracker.getMaxMapTasks(), totalMapSlots);
- }
- @Override
- public boolean canAssignReduce(TaskTrackerStatus tracker,
- int totalRunnableReduces, int totalReduceSlots) {
- return tracker.countReduceTasks() < getCap(totalRunnableReduces,
- tracker.getMaxReduceTasks(), totalReduceSlots);
- }
- }