对一般小公司来说 可能yarn调度能力足够了 但是对于大规模集群1000 or 2000+的话 yarn的调度性能捉襟见肘
恰好网上看到一篇很好的文章https://tech.meituan.com/2019/08/01/hadoop-yarn-scheduling-performance-optimization-practice.html
参考了YARN-5969 发现hadoop2.9.0已经修正了该issue 实测提高了调度性能
FairScheduler 调度方式有两种
心跳调度:Yarn的NodeManager会通过心跳的方式定期向ResourceManager汇报自身状态 伴随着这次rpc请求 会触发Resourcemanager 触发nodeUpdate()方法 为这个节点进行一次资源调度
持续调度:有一个固定守护线程每隔很短的时间调度 实时的资源分配，与NodeManager的心跳出发的调度相互异步并行进行
- 每次dataNode 发来心跳 时候作为一个event走下面方法
FairScheduler 类
@Override
public void handle(SchedulerEvent event) {
switch (event.getType()) {
case NODE_ADDED:
if (!(event instanceof NodeAddedSchedulerEvent)) {
throw new RuntimeException("Unexpected event type: " + event);
}
NodeAddedSchedulerEvent nodeAddedEvent = (NodeAddedSchedulerEvent)event;
addNode(nodeAddedEvent.getContainerReports(),
nodeAddedEvent.getAddedRMNode());
break;
case NODE_REMOVED:
if (!(event instanceof NodeRemovedSchedulerEvent)) {
throw new RuntimeException("Unexpected event type: " + event);
}
NodeRemovedSchedulerEvent nodeRemovedEvent = (NodeRemovedSchedulerEvent)event;
removeNode(nodeRemovedEvent.getRemovedRMNode());
break;
case NODE_UPDATE:
if (!(event instanceof NodeUpdateSchedulerEvent)) {
throw new RuntimeException("Unexpected event type: " + event);
}
NodeUpdateSchedulerEvent nodeUpdatedEvent = (NodeUpdateSchedulerEvent)event;
nodeUpdate(nodeUpdatedEvent.getRMNode());
break;
case APP_ADDED:
if (!(event instanceof AppAddedSchedulerEvent)) {
throw new RuntimeException("Unexpected event type: " + event);
}
AppAddedSchedulerEvent appAddedEvent = (AppAddedSchedulerEvent) event;
每次nodeUpdate 走的都是相同的逻辑
attemptScheduling(node) 持续调度跟心跳调度都走该方法
// If the node is decommissioning, send an update to have the total
// resource equal to the used resource, so no available resource to
// schedule.
if (nm.getState() == NodeState.DECOMMISSIONING) {
this.rmContext
.getDispatcher()
.getEventHandler()
.handle(
new RMNodeResourceUpdateEvent(nm.getNodeID(), ResourceOption
.newInstance(getSchedulerNode(nm.getNodeID())
.getUsedResource(), 0)));
} if (continuousSchedulingEnabled) {
if (!completedContainers.isEmpty()) { //持续调度开启时
attemptScheduling(node);
}
} else {
attemptScheduling(node); //心跳调度
} // Updating node resource utilization
node.setAggregatedContainersUtilization(
nm.getAggregatedContainersUtilization());
node.setNodeUtilization(nm.getNodeUtilization());
持续调度是一个单独的守护线程
间隔getContinuousSchedulingSleepMs()时间运行一次continuousSchedulingAttempt方法
/**
* Thread which attempts scheduling resources continuously,
* asynchronous to the node heartbeats.
*/
private class ContinuousSchedulingThread extends Thread { @Override
public void run() {
while (!Thread.currentThread().isInterrupted()) {
try {
continuousSchedulingAttempt();
Thread.sleep(getContinuousSchedulingSleepMs());
} catch (InterruptedException e) {
LOG.warn("Continuous scheduling thread interrupted. Exiting.", e);
return;
}
}
}
}
之后进行一次node节点 根据资源宽松情况的排序
void continuousSchedulingAttempt() throws InterruptedException {
long start = getClock().getTime();
List<NodeId> nodeIdList = new ArrayList<NodeId>(nodes.keySet());
// Sort the nodes by space available on them, so that we offer
// containers on emptier nodes first, facilitating an even spread. This
// requires holding the scheduler lock, so that the space available on a
// node doesn't change during the sort.
synchronized (this) {
Collections.sort(nodeIdList, nodeAvailableResourceComparator);
}
// iterate all nodes
for (NodeId nodeId : nodeIdList) {
FSSchedulerNode node = getFSSchedulerNode(nodeId);
try {
if (node != null && Resources.fitsIn(minimumAllocation,
node.getAvailableResource())) {
attemptScheduling(node);
}
} catch (Throwable ex) {
LOG.error("Error while attempting scheduling for node " + node +
": " + ex.toString(), ex);
if ((ex instanceof YarnRuntimeException) &&
(ex.getCause() instanceof InterruptedException)) {
// AsyncDispatcher translates InterruptedException to
// YarnRuntimeException with cause InterruptedException.
// Need to throw InterruptedException to stop schedulingThread.
throw (InterruptedException)ex.getCause();
}
}
}
依次对node遍历分配Container
queueMgr.getRootQueue().assignContainer(node) 从root遍历树 对抽象的应用资源遍历
boolean validReservation = false;
FSAppAttempt reservedAppSchedulable = node.getReservedAppSchedulable();
if (reservedAppSchedulable != null) {
validReservation = reservedAppSchedulable.assignReservedContainer(node);
}
if (!validReservation) {
// No reservation, schedule at queue which is farthest below fair share
int assignedContainers = 0;
Resource assignedResource = Resources.clone(Resources.none());
Resource maxResourcesToAssign =
Resources.multiply(node.getAvailableResource(), 0.5f);
while (node.getReservedContainer() == null) {
boolean assignedContainer = false;
Resource assignment = queueMgr.getRootQueue().assignContainer(node);
if (!assignment.equals(Resources.none())) { //判断是否分配到container
assignedContainers++;
assignedContainer = true;
Resources.addTo(assignedResource, assignment);
}
if (!assignedContainer) { break; }
if (!shouldContinueAssigning(assignedContainers,
maxResourcesToAssign, assignedResource)) {
break;
}
}
接下来在assignContainer 方法中对子队列使用特定的比较器排序这里是fairSchduler
@Override
public Resource assignContainer(FSSchedulerNode node) { 对于每一个服务器，对资源树进行一次递归搜索
Resource assigned = Resources.none(); // If this queue is over its limit, reject
if (!assignContainerPreCheck(node)) {
return assigned;
} // Hold the write lock when sorting childQueues
writeLock.lock();
try {
Collections.sort(childQueues, policy.getComparator());
} finally {
writeLock.unlock();
}
对队列下的app排序
/*
* We are releasing the lock between the sort and iteration of the
* "sorted" list. There could be changes to the list here:
* 1. Add a child queue to the end of the list, this doesn't affect
* container assignment.
* 2. Remove a child queue, this is probably good to take care of so we
* don't assign to a queue that is going to be removed shortly.
*/
readLock.lock();
try {
for (FSQueue child : childQueues) {
assigned = child.assignContainer(node);
if (!Resources.equals(assigned, Resources.none())) {
break;
}
}
} finally {
readLock.unlock();
}
return assigned;
assignContainer 可能传入的是app 可能传入的是一个队列 是队列的话 进行递归 直到找到app为止（root(FSParentQueue)节点递归调用assignContainer()，最终将到达最终叶子节点的assignContainer()方法，才真正开始进行分配）
优化一 : 优化队列比较器
我们在这里 关注的就是排序
hadoop2.8.4 排序类 FairSharePolicy中的 根据权重 需求的资源大小 和内存占比 进行排序 多次获取
getResourceUsage() 产生了大量重复计算 这个方法是一个动态获取的过程(耗时)
@Override
public int compare(Schedulable s1, Schedulable s2) {
double minShareRatio1, minShareRatio2;
double useToWeightRatio1, useToWeightRatio2;
Resource minShare1 = Resources.min(RESOURCE_CALCULATOR, null,
s1.getMinShare(), s1.getDemand());
Resource minShare2 = Resources.min(RESOURCE_CALCULATOR, null,
s2.getMinShare(), s2.getDemand());
boolean s1Needy = Resources.lessThan(RESOURCE_CALCULATOR, null,
s1.getResourceUsage(), minShare1);
boolean s2Needy = Resources.lessThan(RESOURCE_CALCULATOR, null,
s2.getResourceUsage(), minShare2);
minShareRatio1 = (double) s1.getResourceUsage().getMemorySize()
/ Resources.max(RESOURCE_CALCULATOR, null, minShare1, ONE).getMemorySize();
minShareRatio2 = (double) s2.getResourceUsage().getMemorySize()
/ Resources.max(RESOURCE_CALCULATOR, null, minShare2, ONE).getMemorySize();
useToWeightRatio1 = s1.getResourceUsage().getMemorySize() /
s1.getWeights().getWeight(ResourceType.MEMORY);
useToWeightRatio2 = s2.getResourceUsage().getMemorySize() /
s2.getWeights().getWeight(ResourceType.MEMORY);
int res = 0;
if (s1Needy && !s2Needy)
res = -1;
else if (s2Needy && !s1Needy)
res = 1;
else if (s1Needy && s2Needy)
res = (int) Math.signum(minShareRatio1 - minShareRatio2);
else
// Neither schedulable is needy
res = (int) Math.signum(useToWeightRatio1 - useToWeightRatio2);
if (res == 0) {
// Apps are tied in fairness ratio. Break the tie by submit time and job
// name to get a deterministic ordering, which is useful for unit tests.
res = (int) Math.signum(s1.getStartTime() - s2.getStartTime());
if (res == 0)
res = s1.getName().compareTo(s2.getName());
}
return res;
}
}
新版优化后如下
@Override
public int compare(Schedulable s1, Schedulable s2) {
int res = compareDemand(s1, s2); // Pre-compute resource usages to avoid duplicate calculation
Resource resourceUsage1 = s1.getResourceUsage();
Resource resourceUsage2 = s2.getResourceUsage(); if (res == 0) {
res = compareMinShareUsage(s1, s2, resourceUsage1, resourceUsage2);
} if (res == 0) {
res = compareFairShareUsage(s1, s2, resourceUsage1, resourceUsage2);
} // Break the tie by submit time
if (res == 0) {
res = (int) Math.signum(s1.getStartTime() - s2.getStartTime());
} // Break the tie by job name
if (res == 0) {
res = s1.getName().compareTo(s2.getName());
} return res;
} private int compareDemand(Schedulable s1, Schedulable s2) {
int res = 0;
Resource demand1 = s1.getDemand();
Resource demand2 = s2.getDemand();
if (demand1.equals(Resources.none()) && Resources.greaterThan(
RESOURCE_CALCULATOR, null, demand2, Resources.none())) {
res = 1;
} else if (demand2.equals(Resources.none()) && Resources.greaterThan(
RESOURCE_CALCULATOR, null, demand1, Resources.none())) {
res = -1;
}
return res;
} private int compareMinShareUsage(Schedulable s1, Schedulable s2,
Resource resourceUsage1, Resource resourceUsage2) {
int res;
Resource minShare1 = Resources.min(RESOURCE_CALCULATOR, null,
s1.getMinShare(), s1.getDemand());
Resource minShare2 = Resources.min(RESOURCE_CALCULATOR, null,
s2.getMinShare(), s2.getDemand());
boolean s1Needy = Resources.lessThan(RESOURCE_CALCULATOR, null,
resourceUsage1, minShare1);
boolean s2Needy = Resources.lessThan(RESOURCE_CALCULATOR, null,
resourceUsage2, minShare2); if (s1Needy && !s2Needy) {
res = -1;
} else if (s2Needy && !s1Needy) {
res = 1;
} else if (s1Needy && s2Needy) {
double minShareRatio1 = (double) resourceUsage1.getMemorySize() /
Resources.max(RESOURCE_CALCULATOR, null, minShare1, ONE)
.getMemorySize();
double minShareRatio2 = (double) resourceUsage2.getMemorySize() /
Resources.max(RESOURCE_CALCULATOR, null, minShare2, ONE)
.getMemorySize();
res = (int) Math.signum(minShareRatio1 - minShareRatio2);
} else {
res = 0;
} return res;
} /**
* To simplify computation, use weights instead of fair shares to calculate
* fair share usage.
*/
private int compareFairShareUsage(Schedulable s1, Schedulable s2,
Resource resourceUsage1, Resource resourceUsage2) {
double weight1 = s1.getWeights().getWeight(ResourceType.MEMORY);
double weight2 = s2.getWeights().getWeight(ResourceType.MEMORY);
double useToWeightRatio1;
double useToWeightRatio2;
if (weight1 > 0.0 && weight2 > 0.0) {
useToWeightRatio1 = resourceUsage1.getMemorySize() / weight1;
useToWeightRatio2 = resourceUsage2.getMemorySize() / weight2;
} else { // Either weight1 or weight2 equals to 0
if (weight1 == weight2) {
// If they have same weight, just compare usage
useToWeightRatio1 = resourceUsage1.getMemorySize();
useToWeightRatio2 = resourceUsage2.getMemorySize();
} else {
// By setting useToWeightRatios to negative weights, we give the
// zero-weight one less priority, so the non-zero weight one will
// be given slots.
useToWeightRatio1 = -weight1;
useToWeightRatio2 = -weight2;
}
} return (int) Math.signum(useToWeightRatio1 - useToWeightRatio2);
} }
用了测试环境集群 比较了修改前后两次队列排序耗时
图中使用挫劣的方式比对 请观众凑合看吧^-^
上面红框里为 新版本 下面红框为老版本 虽然没有进行压测 但是在同样的调度任务前提下 是有说服力的 在大集群上每秒调度上千万乃至上亿次该方法时 调度优化变的明显
上线压测时 在1000队列 1500 pending任务600running任务时 调度性能提高了一倍 还是比较明显的提升的
优化二 : 优化yarn调度逻辑
思想:在大规模集群中 资源利用率表现的并不好，为了提高资源利用率，开启持续调度 然而实践发现 资源利用率是上去了但是 集群调度能力很弱 处理跟释放的container并没有提高
排查原因是心跳调度跟持续调度 走相同的synchronized 方法修饰的attemptScheduling 导致竞争锁 分配和释放都变的缓慢 且队列排序分配 在集群pending任务巨多时异常缓慢
优化:1,启用持续调度 禁用心跳调度
2，持续调度按批进行 间接减少队列排序造成的耗时影响
3. 释放不重要的锁 解放性能
说干就干
开启yarn的持续调度 配置如下:
<property>
<name>yarn.scheduler.fair.continuous-scheduling-enabled</name>
<value>true</value>
<discription>是否打开连续调度功能</discription>
</property>
<property>
持续调度 每5ms执行一次上述方法 对node依次迭代执行
void continuousSchedulingAttempt() throws InterruptedException {
long start = getClock().getTime();
List<NodeId> nodeIdList = new ArrayList<NodeId>(nodes.keySet());
// Sort the nodes by space available on them, so that we offer
// containers on emptier nodes first, facilitating an even spread. This
// requires holding the scheduler lock, so that the space available on a
// node doesn't change during the sort.
synchronized (this) {
Collections.sort(nodeIdList, nodeAvailableResourceComparator); //对所有node 根据资源排序
}
// iterate all nodes
for (NodeId nodeId : nodeIdList) { //遍历所有的node
FSSchedulerNode node = getFSSchedulerNode(nodeId);
try {
if (node != null && Resources.fitsIn(minimumAllocation,
node.getAvailableResource())) { //判断该node 上现有的资源是否大于最小配置资源单位
attemptScheduling(node); //执行ttemptScheduling方法
} } catch (Throwable ex) { LOG.error("Error while attempting scheduling for node " + node + ": " + ex.toString(), ex); if ((ex instanceof YarnRuntimeException) && (ex.getCause() instanceof InterruptedException)) { // AsyncDispatcher translates InterruptedException to // YarnRuntimeException with cause InterruptedException. // Need to throw InterruptedException to stop schedulingThread. throw (InterruptedException)ex.getCause(); } } }
下面看下attemptScheduling方法
@VisibleForTesting
synchronized void attemptScheduling(FSSchedulerNode node) {
if (rmContext.isWorkPreservingRecoveryEnabled()
&& !rmContext.isSchedulerReadyForAllocatingContainers()) {
return;
} final NodeId nodeID = node.getNodeID();
if (!nodes.containsKey(nodeID)) { //合法性
// The node might have just been removed while this thread was waiting
// on the synchronized lock before it entered this synchronized method
LOG.info("Skipping scheduling as the node " + nodeID +
" has been removed");
return;
} // Assign new containers...
// 1. Check for reserved applications
// 2. Schedule if there are no reservations boolean validReservation = false;
FSAppAttempt reservedAppSchedulable = node.getReservedAppSchedulable();
if (reservedAppSchedulable != null) {
validReservation = reservedAppSchedulable.assignReservedContainer(node);
}
if (!validReservation) { //合法性判断
// No reservation, schedule at queue which is farthest below fair share
int assignedContainers = 0;
Resource assignedResource = Resources.clone(Resources.none());
Resource maxResourcesToAssign =
Resources.multiply(node.getAvailableResource(), 0.5f); //默认使用该node最大50%的资源
while (node.getReservedContainer() == null) {
boolean assignedContainer = false;
Resource assignment = queueMgr.getRootQueue().assignContainer(node); //主要方法 依次对root树 遍历直到app 对该node上分配container
if (!assignment.equals(Resources.none())) { //分配到资源
assignedContainers++; //分配到的container个数增1
assignedContainer = true;
Resources.addTo(assignedResource, assignment);
}
if (!assignedContainer) { break; } //未匹配到 跳出
if (!shouldContinueAssigning(assignedContainers, //根据相关配置判断 现在分配的container个数 是否超出node上配置最大数 或node上的可用资源是否超出最小的配置资源
maxResourcesToAssign, assignedResource)) {
break;
}
}
}
updateRootQueueMetrics();
}
针对上面源码 修改为如下内容:
interface Schedulable 接口新增 方法
/**
* Assign list container list this node if possible, and return the amount of
* resources assigned.
*/
public List<Resource> assignContainers(List<FSSchedulerNode> nodes);
@VisibleForTesting
protected void attemptSchedulings(ArrayList<FSSchedulerNode> fsSchedulerNodeList) {
if (rmContext.isWorkPreservingRecoveryEnabled()
&& !rmContext.isSchedulerReadyForAllocatingContainers()) {
return;
}
List<FSSchedulerNode> fsSchedulerNodes = new ArrayList(); //定义个新集合 添加通过检查的node 抽象对象
fsSchedulerNodeList.stream().forEach(node -> {
final NodeId nodeID = node.getNodeID();
if (nodes.containsKey(nodeID)) {
// Assign new containers...// 1. Check for reserved applications
// 2. Schedule if there are no reservations
boolean validReservation = false;
FSAppAttempt reservedAppSchedulable = node.getReservedAppSchedulable();
if (reservedAppSchedulable != null) {
validReservation = reservedAppSchedulable.assignReservedContainer(node);
}
if (!validReservation) { //通过合法检查
if (node.getReservedContainer() == null) { //该node上 没有被某个container预留
fsSchedulerNodes.add(node);
}
}
} else {
LOG.info("Skipping scheduling as the node " + nodeID +
" has been removed");
}
});
if (fsSchedulerNodes.isEmpty()) {
LOG.error("Handle fsSchedulerNodes empty and return");
return;
}
LOG.info("符合条件的nodes:" + fsSchedulerNodeList.size());
List<Resource> resources = queueMgr.getRootQueue().assignContainers(fsSchedulerNodes); //传入node的集合 批量操作
fsOpDurations.addDistributiveContainer(resources.size());
LOG.info("本次分配的container count:" + resources.size());
updateRootQueueMetrics();
}
FSParentQueue 类中 添加实现
@Override
public List<Resource> assignContainers(List<FSSchedulerNode> nodes) {
List<Resource> assignedsNeed = new ArrayList<>();
ArrayList<FSSchedulerNode> fsSchedulerNodes = new ArrayList<>();
for (FSSchedulerNode node : nodes) {
if (assignContainerPreCheck(node)) {
fsSchedulerNodes.add(node);
}
}
if (fsSchedulerNodes.isEmpty()) {
LOG.info("Nodes is empty, skip this assign around");
return assignedsNeed;
} // Hold the write lock when sorting childQueues
writeLock.lock();
try {
Collections.sort(childQueues, policy.getComparator()); //排序又见排序 哈哈
} finally {
writeLock.unlock();
} /*
* We are releasing the lock between the sort and iteration of the
* "sorted" list. There could be changes to the list here:
* 1. Add a child queue to the end of the list, this doesn't affect
* container assignment.
* 2. Remove a child queue, this is probably good to take care of so we
* don't assign to a queue that is going to be removed shortly.
*/
readLock.lock();
try {
for (FSQueue child : childQueues) {
List<Resource> assigneds = child.assignContainers(fsSchedulerNodes); //同样传入node集合
if (!assigneds.isEmpty()) {
for (Resource assign : assigneds) {
assignedsNeed.add(assign);
}
break;
}
}
} finally {
readLock.unlock();
} return assignedsNeed;
}
app最终在FSLeafQueue节点上得到处理
@Override
public List<Resource> assignContainers(List<FSSchedulerNode> nodes) {
Resource assigned = Resources.none();
List<Resource> assigneds = new ArrayList<>();
ArrayList<FSSchedulerNode> fsSchedulerNodes = new ArrayList<>();
for (FSSchedulerNode node : nodes) {
if (assignContainerPreCheck(node)) {
fsSchedulerNodes.add(node);
}
}
if (fsSchedulerNodes.isEmpty()) {
LOG.info("Nodes is empty, skip this assign around");
return assigneds;
}
// Apps that have resource demands.
TreeSet<FSAppAttempt> pendingForResourceApps =
new TreeSet<FSAppAttempt>(policy.getComparator());
readLock.lock();
try {
for (FSAppAttempt app : runnableApps) { //所有的app running or pending 队列 进行依次排序
Resource pending = app.getAppAttemptResourceUsage().getPending();
if (!pending.equals(Resources.none())) { //有资源需求的加入排序队列
pendingForResourceApps.add(app);
}
}
} finally {
readLock.unlock();
} int count = 0; //每个node 分配container计数
Set<String> repeatApp = new HashSet<>(); //定义去重集合
for (FSSchedulerNode node : fsSchedulerNodes) { //node 遍历
count = 0;
for (FSAppAttempt sched : pendingForResourceApps) { //app遍历
// One node just allocate for one app once
if (repeatApp.contains(sched.getId())) { //去重
continue;
}
if (SchedulerAppUtils.isPlaceBlacklisted(sched, node, LOG)) { //判断app有没有在node黑名单里
continue;
}
if (node.getReservedContainer() == null
&& Resources.fitsIn(minimumAllocation, node.getAvailableResource())) { //判断node上还有没有资源
assigned = sched.assignContainer(node); //具体分配container方法
if (!assigned.equals(Resources.none())) {//给container 在node上分配到了资源
count++;
repeatApp.add(sched.getId());
assigneds.add(assigned);
if (LOG.isDebugEnabled()) {
LOG.debug("Assigned container in queue:" + getName() + " " +
"container:" + assigned);
}
}
}
if (count >= maxNodeContainerAssign) { //node 分配的数量 超出最大的配置数 跳出 给下一node 分配
break;
}
}
}
return assigneds;
}
这轮优化 完毕 对比之前 调度性能提高了四倍样子 线上的积压问题得到有效解决
优化后nodeUpdate耗时对比如下
