Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/2388#discussion_r75697458
--- 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.
+ *
+ * @param resourceId The ResourceID of the TaskManager
+ */
+ public void notifyTaskManagerFailure(final ResourceID resourceId) {
+ LOG.info("Resource:{} been notified failure", resourceId);
+ final Map<SlotID, ResourceSlot> slotIdsToRemove =
registeredSlots.remove(resourceId);
+ if (slotIdsToRemove == null) {
+ return;
+ }
--- End diff --
We could also write `if (slotsIdsToRemove != null) { for ... }`
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