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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4347) Implement SlotManager core
Date Mon, 22 Aug 2016 15:19:20 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15430970#comment-15430970
] 

ASF GitHub Bot commented on FLINK-4347:
---------------------------------------

Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2388#discussion_r75697328
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/clusterframework/SlotManager.java
---
    @@ -0,0 +1,519 @@
    +/*
    + * 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.clusterframework;
    +
    +import com.google.common.collect.BiMap;
    +import com.google.common.collect.HashBiMap;
    +import org.apache.flink.annotation.VisibleForTesting;
    +import org.apache.flink.runtime.clusterframework.types.AllocationID;
    +import org.apache.flink.runtime.clusterframework.types.ResourceID;
    +import org.apache.flink.runtime.clusterframework.types.ResourceProfile;
    +import org.apache.flink.runtime.clusterframework.types.ResourceSlot;
    +import org.apache.flink.runtime.clusterframework.types.SlotID;
    +import org.apache.flink.runtime.rpc.resourcemanager.ResourceManagerGateway;
    +import org.apache.flink.runtime.rpc.resourcemanager.SlotRequest;
    +import org.apache.flink.runtime.rpc.taskexecutor.SlotReport;
    +import org.apache.flink.runtime.rpc.taskexecutor.SlotStatus;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import java.util.HashMap;
    +import java.util.LinkedHashMap;
    +import java.util.Map;
    +
    +import static org.apache.flink.util.Preconditions.checkNotNull;
    +
    +/**
    + * SlotManager is responsible for receiving slot requests and do slot allocations. It
allows to request
    + * slots from registered TaskManagers and issues container allocation requests in case
of there are not
    + * enough available slots. Besides, it should sync its slot allocation with TaskManager's
heartbeat.
    + * <p>
    + * The main operation principle of SlotManager is:
    + * <ul>
    + * <li>1. All slot allocation status should be synced with TaskManager, which is
the ground truth.</li>
    + * <li>2. All slots that have registered must be tracked, either by free pool or
allocated pool.</li>
    + * <li>3. All slot requests will be handled by best efforts, there is no guarantee
that one request will be
    + * fulfilled in time or correctly allocated. Conflicts or timeout or some special error
will happen, it should
    + * be handled outside SlotManager. SlotManager will make each decision based on the information
it currently
    + * holds.</li>
    + * </ul>
    + * <b>IMPORTANT:</b> This class is <b>Not Thread-safe</b>.
    + */
    +public abstract class SlotManager {
    +
    +	private static final Logger LOG = LoggerFactory.getLogger(SlotManager.class);
    +
    +	/** Gateway to communicate with ResourceManager */
    +	private final ResourceManagerGateway resourceManagerGateway;
    +
    +	/** All registered slots, including free and allocated slots */
    +	private final Map<ResourceID, Map<SlotID, ResourceSlot>> registeredSlots;
    +
    +	/** All pending slot requests, waiting available slots to fulfil */
    +	private final Map<AllocationID, SlotRequest> pendingSlotRequests;
    +
    +	/** All free slots that can be used to be allocated */
    +	private final Map<SlotID, ResourceSlot> freeSlots;
    +
    +	/** All allocations, we can lookup allocations either by SlotID or AllocationID */
    +	private final AllocationMap allocationMap;
    +
    +	public SlotManager(ResourceManagerGateway resourceManagerGateway) {
    +		this.resourceManagerGateway = resourceManagerGateway;
    +		this.registeredSlots = new HashMap<>();
    +		this.pendingSlotRequests = new LinkedHashMap<>();
    +		this.freeSlots = new HashMap<>();
    +		this.allocationMap = new AllocationMap();
    +	}
    +
    +	// ------------------------------------------------------------------------
    +	//  slot managements
    +	// ------------------------------------------------------------------------
    +
    +	/**
    +	 * Request a slot with requirements, we may either fulfill the request or pending it.
Trigger container
    +	 * allocation if we don't have enough resource. If we have free slot which can match
the request, record
    +	 * this allocation and forward the request to TaskManager through ResourceManager (we
want this done by
    +	 * RPC's main thread to avoid race condition).
    +	 *
    +	 * @param request The detailed request of the slot
    +	 */
    +	public void requestSlot(final SlotRequest request) {
    +		if (isRequestDuplicated(request)) {
    +			LOG.warn("Duplicated slot request, AllocationID:{}", request.getAllocationId());
    +			return;
    +		}
    +
    +		// try to fulfil the request with current free slots
    +		ResourceSlot slot = chooseSlotToUse(request, freeSlots);
    +		if (slot != null) {
    +			LOG.info("Assigning SlotID({}) to AllocationID({}), JobID:{}", slot.getSlotId(),
    +				request.getAllocationId(), request.getJobId());
    +
    +			// record this allocation in bookkeeping
    +			allocationMap.addAllocation(slot.getSlotId(), request.getAllocationId());
    +
    +			// remove selected slot from free pool
    +			freeSlots.remove(slot.getSlotId());
    +
    +			// TODO: send slot request to TaskManager
    +		} else {
    +			LOG.info("Does not have enough slot now, pending request and try to allocate new container,
" +
    +				"AllocationID:{}, JobID:{}", request.getAllocationId(), request.getJobId());
    +			allocateContainer(request.getResourceProfile());
    +			pendingSlotRequests.put(request.getAllocationId(), request);
    +		}
    +	}
    +
    +	/**
    +	 * Sync slot status with TaskManager's SlotReport.
    +	 */
    +	public void updateSlotStatus(final SlotReport slotReport) {
    +		for (SlotStatus slotStatus : slotReport.getSlotsStatus()) {
    +			updateSlotStatus(slotStatus);
    +		}
    +	}
    +
    +	/**
    +	 * The slot request to TaskManager may be either failed by rpc communication(timeout,
network error, etc.)
    +	 * or really rejected by TaskManager. We shall retry this request by:
    +	 * <ul>
    +	 * <li>1. verify and clear all the previous allocate information for this request
    +	 * <li>2. try to request slot again
    +	 * </ul>
    +	 * <p>
    +	 * This may cause some duplicate allocation, e.g. the slot request to TaskManager is
successful but the response
    +	 * is lost somehow, so we may request a slot in another TaskManager, this causes two
slots assigned to one request,
    +	 * but it can be taken care of by rejecting registration at JobManager.
    +	 *
    +	 * @param originalRequest The original slot request
    +	 * @param slotId          The target SlotID
    +	 */
    +	public void handleSlotRequestFailedAtTaskManager(final SlotRequest originalRequest,
final SlotID slotId) {
    +		final AllocationID originalAllocationId = originalRequest.getAllocationId();
    +		LOG.info("Slot request failed at TaskManager, SlotID:{}, AllocationID:{}, JobID:{}",
    +			slotId, originalAllocationId, originalRequest.getJobId());
    +
    +		// verify the allocation info before we do anything
    +		if (freeSlots.containsKey(slotId)) {
    +			// this slot is currently empty, no need to de-allocate it from our allocations
    +			LOG.info("Original slot is somehow empty, retrying this request");
    +
    +			// before retry, we should double check whether this request was allocated by some
other ways
    +			if (!allocationMap.isAllocated(originalAllocationId)) {
    +				requestSlot(originalRequest);
    +			} else {
    +				LOG.info("The failed request is somehow been allocated, SlotID:{}",
    +					allocationMap.getSlotID(originalAllocationId));
    +			}
    +		} else if (allocationMap.isAllocated(slotId)) {
    +			final AllocationID currentAllocationId = allocationMap.getAllocationID(slotId);
    +
    +			// check whether we have an agreement on whom this slot belongs to
    +			if (originalAllocationId.equals(currentAllocationId)) {
    +				LOG.info("De-allocate this request and retry");
    +				allocationMap.removeAllocation(currentAllocationId);
    +
    +				// put this slot back to free pool
    +				ResourceSlot slot = checkNotNull(getRegisteredSlot(slotId));
    +				freeSlots.put(slotId, slot);
    +
    +				// retry the request
    +				requestSlot(originalRequest);
    +			} else {
    +				// the slot is taken by someone else, no need to de-allocate it from our allocations
    +				LOG.info("Original slot is taken by someone else, current AllocationID:{}", currentAllocationId);
    +
    +				// before retry, we should double check whether this request was allocated by some
other ways
    +				if (!allocationMap.isAllocated(originalAllocationId)) {
    +					requestSlot(originalRequest);
    +				} else {
    +					LOG.info("The failed request is somehow been allocated, SlotID:{}",
    +						allocationMap.getSlotID(originalAllocationId));
    +				}
    +			}
    +		} else {
    +			LOG.error("BUG! {} is neither in free pool nor in allocated pool", slotId);
    +		}
    +	}
    +
    +	/**
    +	 * TaskManager been notified failure, we should clean up all its slots.
    --- End diff --
    
    Maybe: "Callback for task manager failures. In case that a task manager fails, we have
to clean up all its slots."


> Implement SlotManager core
> --------------------------
>
>                 Key: FLINK-4347
>                 URL: https://issues.apache.org/jira/browse/FLINK-4347
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Cluster Management
>            Reporter: Kurt Young
>            Assignee: Kurt Young
>
> The slot manager is responsible to maintain the list of slot requests and slot allocations.
It allows to request slots from the registered TaskExecutors and issues container allocation
requests in case that there are not enough available resources.



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