org.apache.flink.runtime.jobmaster.slotpool.PreviousAllocationSlotSelectionStrategy 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.runtime.jobmaster.slotpool;

import org.apache.flink.runtime.clusterframework.types.AllocationID;
import org.apache.flink.runtime.clusterframework.types.SlotProfile;
import org.apache.flink.runtime.jobmanager.scheduler.Locality;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nonnull;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Optional;
import java.util.Set;

/**
 * This class implements a {@link SlotSelectionStrategy} that is based on previous allocations and
 * falls back to using location preference hints if there is no previous allocation.
 */
public class PreviousAllocationSlotSelectionStrategy implements SlotSelectionStrategy {

    private static final Logger LOG =
            LoggerFactory.getLogger(PreviousAllocationSlotSelectionStrategy.class);

    private final SlotSelectionStrategy fallbackSlotSelectionStrategy;

    private PreviousAllocationSlotSelectionStrategy(
            SlotSelectionStrategy fallbackSlotSelectionStrategy) {
        this.fallbackSlotSelectionStrategy = fallbackSlotSelectionStrategy;
    }

    @Override
    public Optional selectBestSlotForProfile(
            @Nonnull Collection availableSlots,
            @Nonnull SlotProfile slotProfile) {

        LOG.debug("Select best slot for profile {}.", slotProfile);

        Collection priorAllocations = slotProfile.getPreferredAllocations();

        // First, if there was a prior allocation try to schedule to the same/old slot
        if (!priorAllocations.isEmpty()) {
            for (SlotInfoAndResources availableSlot : availableSlots) {
                if (priorAllocations.contains(availableSlot.getSlotInfo().getAllocationId())) {
                    return Optional.of(
                            SlotInfoAndLocality.of(availableSlot.getSlotInfo(), Locality.LOCAL));
                }
            }
        }

        // Second, select based on location preference, excluding blacklisted allocations
        Set blackListedAllocations = slotProfile.getReservedAllocations();
        Collection availableAndAllowedSlots =
                computeWithoutBlacklistedSlots(availableSlots, blackListedAllocations);
        return fallbackSlotSelectionStrategy.selectBestSlotForProfile(
                availableAndAllowedSlots, slotProfile);
    }

    @Nonnull
    private Collection computeWithoutBlacklistedSlots(
            @Nonnull Collection availableSlots,
            @Nonnull Set blacklistedAllocations) {

        if (blacklistedAllocations.isEmpty()) {
            return Collections.unmodifiableCollection(availableSlots);
        }

        ArrayList availableAndAllowedSlots =
                new ArrayList<>(availableSlots.size());
        for (SlotInfoAndResources availableSlot : availableSlots) {
            if (!blacklistedAllocations.contains(availableSlot.getSlotInfo().getAllocationId())) {
                availableAndAllowedSlots.add(availableSlot);
            }
        }

        return availableAndAllowedSlots;
    }

    public static PreviousAllocationSlotSelectionStrategy create() {
        return create(LocationPreferenceSlotSelectionStrategy.createDefault());
    }

    public static PreviousAllocationSlotSelectionStrategy create(
            SlotSelectionStrategy fallbackSlotSelectionStrategy) {
        return new PreviousAllocationSlotSelectionStrategy(fallbackSlotSelectionStrategy);
    }
}