YARN-4524. Cleanup AppSchedulingInfo. (Karthik Kambatla via wangda)

This commit is contained in:
Wangda Tan 2015-12-30 15:36:55 -08:00
parent 6eefae1b33
commit 05fa852d75
3 changed files with 175 additions and 210 deletions

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@ -26,6 +26,8 @@ Release 2.9.0 - UNRELEASED
YARN-4522. Queue acl can be checked at app submission. (Jian He via wangda)
YARN-4524. Cleanup AppSchedulingInfo. (Karthik Kambatla via wangda)
OPTIMIZATIONS
BUG FIXES

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@ -20,6 +20,7 @@ package org.apache.hadoop.yarn.server.resourcemanager.scheduler;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
@ -42,7 +43,6 @@ import org.apache.hadoop.yarn.api.records.NodeId;
import org.apache.hadoop.yarn.api.records.Priority;
import org.apache.hadoop.yarn.api.records.Resource;
import org.apache.hadoop.yarn.api.records.ResourceRequest;
import org.apache.hadoop.yarn.server.resourcemanager.rmapp.attempt.RMAppAttemptState;
import org.apache.hadoop.yarn.server.resourcemanager.rmcontainer.RMContainer;
import org.apache.hadoop.yarn.server.resourcemanager.rmcontainer.RMContainerState;
import org.apache.hadoop.yarn.util.resource.Resources;
@ -56,40 +56,36 @@ import org.apache.hadoop.yarn.util.resource.Resources;
public class AppSchedulingInfo {
private static final Log LOG = LogFactory.getLog(AppSchedulingInfo.class);
private static final Comparator COMPARATOR =
new org.apache.hadoop.yarn.server.resourcemanager.resource.Priority.Comparator();
private static final int EPOCH_BIT_SHIFT = 40;
private final ApplicationId applicationId;
private final ApplicationAttemptId applicationAttemptId;
final ApplicationId applicationId;
private String queueName;
Queue queue;
final String user;
// TODO making containerIdCounter long
private final AtomicLong containerIdCounter;
private final int EPOCH_BIT_SHIFT = 40;
private final String user;
final Set<Priority> priorities = new TreeSet<Priority>(
new org.apache.hadoop.yarn.server.resourcemanager.resource.Priority.Comparator());
final Map<Priority, Map<String, ResourceRequest>> resourceRequestMap =
new ConcurrentHashMap<Priority, Map<String, ResourceRequest>>();
final Map<NodeId, Map<Priority, Map<ContainerId,
SchedContainerChangeRequest>>> increaseRequestMap =
new ConcurrentHashMap<>();
private Set<String> userBlacklist = new HashSet<>();
private Set<String> amBlacklist = new HashSet<>();
//private final ApplicationStore store;
private Queue queue;
private ActiveUsersManager activeUsersManager;
/* Allocated by scheduler */
boolean pending = true; // for app metrics
private boolean pending = true; // whether accepted/allocated by scheduler
private ResourceUsage appResourceUsage;
private final Set<String> amBlacklist = new HashSet<>();
private Set<String> userBlacklist = new HashSet<>();
final Set<Priority> priorities = new TreeSet<>(COMPARATOR);
final Map<Priority, Map<String, ResourceRequest>> resourceRequestMap =
new ConcurrentHashMap<>();
final Map<NodeId, Map<Priority, Map<ContainerId,
SchedContainerChangeRequest>>> containerIncreaseRequestMap =
new ConcurrentHashMap<>();
public AppSchedulingInfo(ApplicationAttemptId appAttemptId,
String user, Queue queue, ActiveUsersManager activeUsersManager,
long epoch, ResourceUsage appResourceUsage) {
this.applicationAttemptId = appAttemptId;
this.applicationId = appAttemptId.getApplicationId();
this.queue = queue;
this.queueName = queue.getQueueName();
this.user = user;
this.activeUsersManager = activeUsersManager;
this.containerIdCounter = new AtomicLong(epoch << EPOCH_BIT_SHIFT);
@ -104,14 +100,18 @@ public class AppSchedulingInfo {
return applicationAttemptId;
}
public String getQueueName() {
return queueName;
}
public String getUser() {
return user;
}
public long getNewContainerId() {
return this.containerIdCounter.incrementAndGet();
}
public synchronized String getQueueName() {
return queue.getQueueName();
}
public synchronized boolean isPending() {
return pending;
}
@ -125,30 +125,23 @@ public class AppSchedulingInfo {
LOG.info("Application " + applicationId + " requests cleared");
}
public long getNewContainerId() {
return this.containerIdCounter.incrementAndGet();
}
public boolean hasIncreaseRequest(NodeId nodeId) {
public synchronized boolean hasIncreaseRequest(NodeId nodeId) {
Map<Priority, Map<ContainerId, SchedContainerChangeRequest>> requestsOnNode =
increaseRequestMap.get(nodeId);
if (null == requestsOnNode) {
return false;
}
return requestsOnNode.size() > 0;
containerIncreaseRequestMap.get(nodeId);
return requestsOnNode == null ? false : requestsOnNode.size() > 0;
}
public Map<ContainerId, SchedContainerChangeRequest>
public synchronized Map<ContainerId, SchedContainerChangeRequest>
getIncreaseRequests(NodeId nodeId, Priority priority) {
Map<Priority, Map<ContainerId, SchedContainerChangeRequest>> requestsOnNode =
increaseRequestMap.get(nodeId);
if (null == requestsOnNode) {
return null;
}
return requestsOnNode.get(priority);
containerIncreaseRequestMap.get(nodeId);
return requestsOnNode == null ? null : requestsOnNode.get(priority);
}
/**
* return true if any of the existing increase requests are updated,
* false if none of them are updated
*/
public synchronized boolean updateIncreaseRequests(
List<SchedContainerChangeRequest> increaseRequests) {
boolean resourceUpdated = false;
@ -157,10 +150,10 @@ public class AppSchedulingInfo {
NodeId nodeId = r.getRMContainer().getAllocatedNode();
Map<Priority, Map<ContainerId, SchedContainerChangeRequest>> requestsOnNode =
increaseRequestMap.get(nodeId);
containerIncreaseRequestMap.get(nodeId);
if (null == requestsOnNode) {
requestsOnNode = new TreeMap<>();
increaseRequestMap.put(nodeId, requestsOnNode);
containerIncreaseRequestMap.put(nodeId, requestsOnNode);
}
SchedContainerChangeRequest prevChangeRequest =
@ -168,22 +161,21 @@ public class AppSchedulingInfo {
if (null != prevChangeRequest) {
if (Resources.equals(prevChangeRequest.getTargetCapacity(),
r.getTargetCapacity())) {
// New target capacity is as same as what we have, just ignore the new
// one
// increase request hasn't changed
continue;
}
// remove the old one
// remove the old one, as we will use the new one going forward
removeIncreaseRequest(nodeId, prevChangeRequest.getPriority(),
prevChangeRequest.getContainerId());
}
if (Resources.equals(r.getTargetCapacity(), r.getRMContainer().getAllocatedResource())) {
if (Resources.equals(r.getTargetCapacity(),
r.getRMContainer().getAllocatedResource())) {
if (LOG.isDebugEnabled()) {
LOG.debug("Trying to increase/decrease container, "
+ "target capacity = previous capacity = " + prevChangeRequest
+ " for container=" + r.getContainerId()
+ ". Will ignore this increase request");
LOG.debug("Trying to increase container " + r.getContainerId()
+ ", target capacity = previous capacity = " + prevChangeRequest
+ ". Will ignore this increase request.");
}
continue;
}
@ -195,25 +187,26 @@ public class AppSchedulingInfo {
return resourceUpdated;
}
// insert increase request and add missing hierarchy if missing
/**
* Insert increase request, adding any missing items in the data-structure
* hierarchy.
*/
private void insertIncreaseRequest(SchedContainerChangeRequest request) {
NodeId nodeId = request.getNodeId();
Priority priority = request.getPriority();
ContainerId containerId = request.getContainerId();
Map<Priority, Map<ContainerId, SchedContainerChangeRequest>> requestsOnNode =
increaseRequestMap.get(nodeId);
containerIncreaseRequestMap.get(nodeId);
if (null == requestsOnNode) {
requestsOnNode =
new HashMap<Priority, Map<ContainerId, SchedContainerChangeRequest>>();
increaseRequestMap.put(nodeId, requestsOnNode);
requestsOnNode = new HashMap<>();
containerIncreaseRequestMap.put(nodeId, requestsOnNode);
}
Map<ContainerId, SchedContainerChangeRequest> requestsOnNodeWithPriority =
requestsOnNode.get(priority);
if (null == requestsOnNodeWithPriority) {
requestsOnNodeWithPriority =
new TreeMap<ContainerId, SchedContainerChangeRequest>();
requestsOnNodeWithPriority = new TreeMap<>();
requestsOnNode.put(priority, requestsOnNodeWithPriority);
}
@ -237,7 +230,7 @@ public class AppSchedulingInfo {
public synchronized boolean removeIncreaseRequest(NodeId nodeId, Priority priority,
ContainerId containerId) {
Map<Priority, Map<ContainerId, SchedContainerChangeRequest>> requestsOnNode =
increaseRequestMap.get(nodeId);
containerIncreaseRequestMap.get(nodeId);
if (null == requestsOnNode) {
return false;
}
@ -256,7 +249,7 @@ public class AppSchedulingInfo {
requestsOnNode.remove(priority);
}
if (requestsOnNode.isEmpty()) {
increaseRequestMap.remove(nodeId);
containerIncreaseRequestMap.remove(nodeId);
}
if (request == null) {
@ -279,18 +272,15 @@ public class AppSchedulingInfo {
public SchedContainerChangeRequest getIncreaseRequest(NodeId nodeId,
Priority priority, ContainerId containerId) {
Map<Priority, Map<ContainerId, SchedContainerChangeRequest>> requestsOnNode =
increaseRequestMap.get(nodeId);
containerIncreaseRequestMap.get(nodeId);
if (null == requestsOnNode) {
return null;
}
Map<ContainerId, SchedContainerChangeRequest> requestsOnNodeWithPriority =
requestsOnNode.get(priority);
if (null == requestsOnNodeWithPriority) {
return null;
}
return requestsOnNodeWithPriority.get(containerId);
return requestsOnNodeWithPriority == null ? null
: requestsOnNodeWithPriority.get(containerId);
}
/**
@ -299,121 +289,120 @@ public class AppSchedulingInfo {
* by the application.
*
* @param requests resources to be acquired
* @param recoverPreemptedRequest recover Resource Request on preemption
* @return true if any resource was updated, false else
* @param recoverPreemptedRequest recover ResourceRequest on preemption
* @return true if any resource was updated, false otherwise
*/
synchronized public boolean updateResourceRequests(
public synchronized boolean updateResourceRequests(
List<ResourceRequest> requests, boolean recoverPreemptedRequest) {
QueueMetrics metrics = queue.getMetrics();
// Flag to track if any incoming requests update "ANY" requests
boolean anyResourcesUpdated = false;
// Update resource requests
for (ResourceRequest request : requests) {
Priority priority = request.getPriority();
String resourceName = request.getResourceName();
boolean updatePendingResources = false;
ResourceRequest lastRequest = null;
if (resourceName.equals(ResourceRequest.ANY)) {
if (LOG.isDebugEnabled()) {
LOG.debug("update:" + " application=" + applicationId + " request="
+ request);
}
updatePendingResources = true;
anyResourcesUpdated = true;
// Premature optimization?
// Assumes that we won't see more than one priority request updated
// in one call, reasonable assumption... however, it's totally safe
// to activate same application more than once.
// Thus we don't need another loop ala the one in decrementOutstanding()
// which is needed during deactivate.
if (request.getNumContainers() > 0) {
activeUsersManager.activateApplication(user, applicationId);
}
ResourceRequest previousAnyRequest =
getResourceRequest(priority, resourceName);
// When there is change in ANY request label expression, we should
// update label for all resource requests already added of same
// priority as ANY resource request.
if ((null == previousAnyRequest)
|| isRequestLabelChanged(previousAnyRequest, request)) {
Map<String, ResourceRequest> resourceRequest =
getResourceRequests(priority);
if (resourceRequest != null) {
for (ResourceRequest r : resourceRequest.values()) {
if (!r.getResourceName().equals(ResourceRequest.ANY)) {
r.setNodeLabelExpression(request.getNodeLabelExpression());
}
}
}
}
} else {
ResourceRequest anyRequest =
getResourceRequest(priority, ResourceRequest.ANY);
if (anyRequest != null) {
request.setNodeLabelExpression(anyRequest.getNodeLabelExpression());
}
}
// Update node labels if required
updateNodeLabels(request);
Map<String, ResourceRequest> asks = this.resourceRequestMap.get(priority);
if (asks == null) {
asks = new ConcurrentHashMap<String, ResourceRequest>();
asks = new ConcurrentHashMap<>();
this.resourceRequestMap.put(priority, asks);
this.priorities.add(priority);
}
lastRequest = asks.get(resourceName);
// Increment number of containers if recovering preempted resources
ResourceRequest lastRequest = asks.get(resourceName);
if (recoverPreemptedRequest && lastRequest != null) {
// Increment the number of containers to 1, as it is recovering a
// single container.
request.setNumContainers(lastRequest.getNumContainers() + 1);
}
// Update asks
asks.put(resourceName, request);
if (updatePendingResources) {
// Similarly, deactivate application?
if (request.getNumContainers() <= 0) {
LOG.info("checking for deactivate of application :"
+ this.applicationId);
checkForDeactivation();
}
int lastRequestContainers = lastRequest != null ? lastRequest
.getNumContainers() : 0;
Resource lastRequestCapability = lastRequest != null ? lastRequest
.getCapability() : Resources.none();
metrics.incrPendingResources(user, request.getNumContainers(),
request.getCapability());
metrics.decrPendingResources(user, lastRequestContainers,
lastRequestCapability);
// update queue:
Resource increasedResource =
Resources.multiply(request.getCapability(),
request.getNumContainers());
queue.incPendingResource(request.getNodeLabelExpression(),
increasedResource);
appResourceUsage.incPending(request.getNodeLabelExpression(),
increasedResource);
if (lastRequest != null) {
Resource decreasedResource =
Resources.multiply(lastRequestCapability, lastRequestContainers);
queue.decPendingResource(lastRequest.getNodeLabelExpression(),
decreasedResource);
appResourceUsage.decPending(lastRequest.getNodeLabelExpression(),
decreasedResource);
if (resourceName.equals(ResourceRequest.ANY)) {
anyResourcesUpdated = true;
// Activate application. Metrics activation is done here.
// TODO: Shouldn't we activate even if numContainers = 0?
if (request.getNumContainers() > 0) {
activeUsersManager.activateApplication(user, applicationId);
}
// Update pendingResources
updatePendingResources(lastRequest, request, queue.getMetrics());
}
}
return anyResourcesUpdated;
}
private boolean isRequestLabelChanged(ResourceRequest requestOne,
private void updatePendingResources(ResourceRequest lastRequest,
ResourceRequest request, QueueMetrics metrics) {
if (request.getNumContainers() <= 0) {
LOG.info("checking for deactivate of application :"
+ this.applicationId);
checkForDeactivation();
}
int lastRequestContainers =
(lastRequest != null) ? lastRequest.getNumContainers() : 0;
Resource lastRequestCapability =
lastRequest != null ? lastRequest.getCapability() : Resources.none();
metrics.incrPendingResources(user,
request.getNumContainers(), request.getCapability());
metrics.decrPendingResources(user,
lastRequestContainers, lastRequestCapability);
// update queue:
Resource increasedResource =
Resources.multiply(request.getCapability(), request.getNumContainers());
queue.incPendingResource(request.getNodeLabelExpression(),
increasedResource);
appResourceUsage.incPending(request.getNodeLabelExpression(),
increasedResource);
if (lastRequest != null) {
Resource decreasedResource =
Resources.multiply(lastRequestCapability, lastRequestContainers);
queue.decPendingResource(lastRequest.getNodeLabelExpression(),
decreasedResource);
appResourceUsage.decPending(lastRequest.getNodeLabelExpression(),
decreasedResource);
}
}
private void updateNodeLabels(ResourceRequest request) {
Priority priority = request.getPriority();
String resourceName = request.getResourceName();
if (resourceName.equals(ResourceRequest.ANY)) {
ResourceRequest previousAnyRequest =
getResourceRequest(priority, resourceName);
// When there is change in ANY request label expression, we should
// update label for all resource requests already added of same
// priority as ANY resource request.
if ((null == previousAnyRequest)
|| hasRequestLabelChanged(previousAnyRequest, request)) {
Map<String, ResourceRequest> resourceRequest =
getResourceRequests(priority);
if (resourceRequest != null) {
for (ResourceRequest r : resourceRequest.values()) {
if (!r.getResourceName().equals(ResourceRequest.ANY)) {
r.setNodeLabelExpression(request.getNodeLabelExpression());
}
}
}
}
} else {
ResourceRequest anyRequest =
getResourceRequest(priority, ResourceRequest.ANY);
if (anyRequest != null) {
request.setNodeLabelExpression(anyRequest.getNodeLabelExpression());
}
}
}
private boolean hasRequestLabelChanged(ResourceRequest requestOne,
ResourceRequest requestTwo) {
String requestOneLabelExp = requestOne.getNodeLabelExpression();
String requestTwoLabelExp = requestTwo.getNodeLabelExpression();
@ -465,24 +454,24 @@ public class AppSchedulingInfo {
}
}
synchronized public Collection<Priority> getPriorities() {
public synchronized Collection<Priority> getPriorities() {
return priorities;
}
synchronized public Map<String, ResourceRequest> getResourceRequests(
public synchronized Map<String, ResourceRequest> getResourceRequests(
Priority priority) {
return resourceRequestMap.get(priority);
}
public List<ResourceRequest> getAllResourceRequests() {
List<ResourceRequest> ret = new ArrayList<ResourceRequest>();
public synchronized List<ResourceRequest> getAllResourceRequests() {
List<ResourceRequest> ret = new ArrayList<>();
for (Map<String, ResourceRequest> r : resourceRequestMap.values()) {
ret.addAll(r.values());
}
return ret;
}
synchronized public ResourceRequest getResourceRequest(Priority priority,
public synchronized ResourceRequest getResourceRequest(Priority priority,
String resourceName) {
Map<String, ResourceRequest> nodeRequests = resourceRequestMap.get(priority);
return (nodeRequests == null) ? null : nodeRequests.get(resourceName);
@ -511,7 +500,7 @@ public class AppSchedulingInfo {
}
}
}
public synchronized void increaseContainer(
SchedContainerChangeRequest increaseRequest) {
NodeId nodeId = increaseRequest.getNodeId();
@ -559,28 +548,17 @@ public class AppSchedulingInfo {
/**
* Resources have been allocated to this application by the resource
* scheduler. Track them.
*
* @param type
* the type of the node
* @param node
* the nodeinfo of the node
* @param priority
* the priority of the request.
* @param request
* the request
* @param container
* the containers allocated.
*/
synchronized public List<ResourceRequest> allocate(NodeType type,
public synchronized List<ResourceRequest> allocate(NodeType type,
SchedulerNode node, Priority priority, ResourceRequest request,
Container container) {
List<ResourceRequest> resourceRequests = new ArrayList<ResourceRequest>();
Container containerAllocated) {
List<ResourceRequest> resourceRequests = new ArrayList<>();
if (type == NodeType.NODE_LOCAL) {
allocateNodeLocal(node, priority, request, container, resourceRequests);
allocateNodeLocal(node, priority, request, resourceRequests);
} else if (type == NodeType.RACK_LOCAL) {
allocateRackLocal(node, priority, request, container, resourceRequests);
allocateRackLocal(node, priority, request, resourceRequests);
} else {
allocateOffSwitch(node, priority, request, container, resourceRequests);
allocateOffSwitch(request, resourceRequests);
}
QueueMetrics metrics = queue.getMetrics();
if (pending) {
@ -592,8 +570,8 @@ public class AppSchedulingInfo {
if (LOG.isDebugEnabled()) {
LOG.debug("allocate: applicationId=" + applicationId
+ " container=" + container.getId()
+ " host=" + container.getNodeId().toString()
+ " container=" + containerAllocated.getId()
+ " host=" + containerAllocated.getNodeId().toString()
+ " user=" + user
+ " resource=" + request.getCapability()
+ " type=" + type);
@ -606,12 +584,9 @@ public class AppSchedulingInfo {
/**
* The {@link ResourceScheduler} is allocating data-local resources to the
* application.
*
* @param allocatedContainers
* resources allocated to the application
*/
synchronized private void allocateNodeLocal(SchedulerNode node,
Priority priority, ResourceRequest nodeLocalRequest, Container container,
private synchronized void allocateNodeLocal(SchedulerNode node,
Priority priority, ResourceRequest nodeLocalRequest,
List<ResourceRequest> resourceRequests) {
// Update future requirements
decResourceRequest(node.getNodeName(), priority, nodeLocalRequest);
@ -641,12 +616,9 @@ public class AppSchedulingInfo {
/**
* The {@link ResourceScheduler} is allocating data-local resources to the
* application.
*
* @param allocatedContainers
* resources allocated to the application
*/
synchronized private void allocateRackLocal(SchedulerNode node,
Priority priority, ResourceRequest rackLocalRequest, Container container,
private synchronized void allocateRackLocal(SchedulerNode node,
Priority priority, ResourceRequest rackLocalRequest,
List<ResourceRequest> resourceRequests) {
// Update future requirements
decResourceRequest(node.getRackName(), priority, rackLocalRequest);
@ -663,20 +635,16 @@ public class AppSchedulingInfo {
/**
* The {@link ResourceScheduler} is allocating data-local resources to the
* application.
*
* @param allocatedContainers
* resources allocated to the application
*/
synchronized private void allocateOffSwitch(SchedulerNode node,
Priority priority, ResourceRequest offSwitchRequest, Container container,
List<ResourceRequest> resourceRequests) {
private synchronized void allocateOffSwitch(
ResourceRequest offSwitchRequest, List<ResourceRequest> resourceRequests) {
// Update future requirements
decrementOutstanding(offSwitchRequest);
// Update cloned OffRack requests for recovery
resourceRequests.add(cloneResourceRequest(offSwitchRequest));
}
synchronized private void decrementOutstanding(
private synchronized void decrementOutstanding(
ResourceRequest offSwitchRequest) {
int numOffSwitchContainers = offSwitchRequest.getNumContainers() - 1;
@ -695,7 +663,7 @@ public class AppSchedulingInfo {
offSwitchRequest.getCapability());
}
synchronized private void checkForDeactivation() {
private synchronized void checkForDeactivation() {
boolean deactivate = true;
for (Priority priority : getPriorities()) {
ResourceRequest request = getResourceRequest(priority, ResourceRequest.ANY);
@ -709,7 +677,7 @@ public class AppSchedulingInfo {
// also we need to check increase request
if (!deactivate) {
deactivate = increaseRequestMap.isEmpty();
deactivate = containerIncreaseRequestMap.isEmpty();
}
if (deactivate) {
@ -717,7 +685,7 @@ public class AppSchedulingInfo {
}
}
synchronized public void move(Queue newQueue) {
public synchronized void move(Queue newQueue) {
QueueMetrics oldMetrics = queue.getMetrics();
QueueMetrics newMetrics = newQueue.getMetrics();
for (Map<String, ResourceRequest> asks : resourceRequestMap.values()) {
@ -741,10 +709,9 @@ public class AppSchedulingInfo {
activeUsersManager = newQueue.getActiveUsersManager();
activeUsersManager.activateApplication(user, applicationId);
this.queue = newQueue;
this.queueName = newQueue.getQueueName();
}
synchronized public void stop(RMAppAttemptState rmAppAttemptFinalState) {
public synchronized void stop() {
// clear pending resources metrics for the application
QueueMetrics metrics = queue.getMetrics();
for (Map<String, ResourceRequest> asks : resourceRequestMap.values()) {
@ -782,12 +749,8 @@ public class AppSchedulingInfo {
public synchronized void transferStateFromPreviousAppSchedulingInfo(
AppSchedulingInfo appInfo) {
// this.priorities = appInfo.getPriorities();
// this.requests = appInfo.getRequests();
// This should not require locking the userBlacklist since it will not be
// used by this instance until after setCurrentAppAttempt.
// Should cleanup this to avoid sharing between instances and can
// then remove getBlacklist as well.
this.userBlacklist = appInfo.getBlackList();
}

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@ -331,7 +331,7 @@ public class SchedulerApplicationAttempt implements SchedulableEntity {
public synchronized void stop(RMAppAttemptState rmAppAttemptFinalState) {
// Cleanup all scheduling information
isStopped = true;
appSchedulingInfo.stop(rmAppAttemptFinalState);
appSchedulingInfo.stop();
}
public synchronized boolean isStopped() {