tomcat 应用服务启动cpu过高

参考资料：https://my.oschina.net/7001/blog/1504798?nocache=1516010315775

1、Linux环境下可以使用top指令查看系统进程占用情况

2、 top -Hp pid（例23399）可以查看进程的线程运行情况

3、jstack 23399|grep -A 10 5d13 （5d13 为线程id的16进制）查看一个进程里面的线程运行情况

操作系统线程运行图

New: 新建状态,当线程对象创建时存在的状态;

 

Runnable:ready-to-run,可运行状态,调用thread.start()后,线程变成为Runnable状态,还需要获得CPU才能运行;

 

Running:正在运行,当调用Thread.yield()或执行完时间片,CPU会重新调度;注意:Thread.yield()调用之后,线程会释放CPU,但是CPU重新调度可能让线程重新获得时间片。

 

Waiting:调用thread.join()、object.wait()和LockSupport.park()线程都会进入该状态,表明线程正处于等待某个资源或条件发生来唤醒自己;thread.join()、object.wait()需要Object的notify()/notifyAll()来唤醒,LockSupport.park()需要LockSupport.unpark()来唤醒,这些方法使线程进入running状态,参与CPU调度。

 

thread.join():作用是等待线程thread终止,只有等thread执行完成后,主线程才会继续向下执行;从join()实现可知,只有thread.isAlive()返回true,才会调用object.wait()进入等待状态,也就是说,thread.start()未被调用,或thread已经结束,object.wait()都不会被调用;若在waiting状态被唤醒,会再次判断thread.isAlive(),若为true,继续调用object.wait()进入waiting状态,直到thread终止,thread.isAlive()返回false。

 

object.wait():作用是使线程进入等待状态,只有线程持有对象上的锁,才能调用该对象的wait(),线程进入等待状态后会释放其持有的该对象上的锁,但会仍然持有其它对象的锁。若其他线程想要调用notify()、notifyAll()唤醒该线程,也需要持有该对象的锁。

 

LockSupport.park():挂起当前线程,不参与线程调度,除非调用LockSupport.unpark()重新参与调度。

 

Timed_Waiting:调用Thread.sleep(long)、LockSupport.parkNanos(long)、thread.join(long)或obj.wait(long)等线程都会进入该状态,与Waiting的区别在于Timed_Waiting的等待有时间限制;

 

Thread.sleep():让当前线程停止运行指定的毫秒数,该线程不会释放其持有的锁等资源。

 

Blocked:指线程正在等待获取锁,当线程进入synchronized保护的代码块或方法时,没有获取到锁,则会进入该状态;或者线程正在等待I/O,也会进入该状态。注意,java中Lock对象不会使线程进入该状态。

 

Dead:线程执行完毕,或者抛出了未捕获的异常之后,会进入dead状态,表示该线程结束。

 

上图中某些状态只是为了方便说明,实际并不存在,如running/sleeping,java中明确定义的线程状态值有如下几个:

 

NEW、RUNNABLE、BLOCKED、WAITING、TIMED_WAITING、TERMINATED

分析jstack日志

大量dubbo线程处于WAITING状态,看日志:

"DubboServerHandler-192.168.10.33:33180-thread-1220" #1700 daemon prio=5 os_prio=0 tid=0x00007f3394988800 nid=0x4aae waiting on condition [0x00007f32d75c0000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for<0x00000000866090c0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1081)
at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

由日志可知道,线程“DubboServerHandler-172.24.16.78:33180-thread-1220”处于WAITING状态,主要是因为从线程池队列中取任务来执行,但线程池为空,最终调用了LockSupport.park使线程进入等待,需要等待队列非空的通知。

 

设想一下,什么时候会新创建新线程来处理请求?结合jdk线程池实现可知,当新请求到来时,若池中线程数量未达到corePoolSize,直接新建线程来处理请求。

 

根据jstack日志,有195个dubbo线程从ScheduledThreadPoolExecutor中取任务导致处于WAITING状态,按理这些dubbo线程应该不会处理调度任务,为什么会去调度任务线程中取任务呢?这里暂时抛出这个问题吧,我也不知道答案,希望有大神帮忙解答。

 

还有一部分WAITING状态的线程,看日志:

"DubboServerHandler-192.168.10.33:33180-thread-1489" #1636 daemon prio=5 os_prio=0 tid=0x00007f33b0122800 nid=0x48ec waiting on condition [0x00007f32db600000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for<0x0000000089d717a8> (a java.util.concurrent.SynchronousQueue$TransferStack)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.SynchronousQueue$TransferStack.awaitFulfill(SynchronousQueue.java:458)
at java.util.concurrent.SynchronousQueue$TransferStack.transfer(SynchronousQueue.java:362)
at java.util.concurrent.SynchronousQueue.take(SynchronousQueue.java:924)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

这部分线程主要是因为从ThreadPoolExecutor取任务来执行时被挂起(309个线程),这部分线程主要是正常处理完请求后,回到线程池等待任务执行。由于这里使用newFixedThreadPool作为dubbo请求处理池,因此每个新请求默认都会创建新线程来处理,除非达到池的限定值。只有达到线程池最大线程数量,哪些阻塞在getTask()的线程才会得到复用。

 

此外,还有大量dubbo线程处于BLOCKED状态,看日志:

"DubboServerHandler-192.168.10.33:33180-thread-236" #1727 daemon prio=5 os_prio=0 tid=0x00007f336403b000 nid=0x4b8b waiting for monitor entry [0x00007f32d58a4000]
java.lang.Thread.State: BLOCKED (on object monitor)
at org.apache.logging.log4j.core.appender.rolling.RollingFileManager.checkRollover(RollingFileManager.java:149)
- waiting to lock <0x0000000085057998> (a org.apache.logging.log4j.core.appender.rolling.RollingRandomAccessFileManager)
at org.apache.logging.log4j.core.appender.RollingRandomAccessFileAppender.append(RollingRandomAccessFileAppender.java:88)
at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:155)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:128)
at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:119)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:390)
at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:375)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:359)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:349)
at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:63)
at org.apache.logging.log4j.core.Logger.logMessage(Logger.java:146)
at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:1993)
at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1852)
at org.apache.logging.slf4j.Log4jLogger.info(Log4jLogger.java:179)
at com.alibaba.dubbo.common.logger.slf4j.Slf4jLogger.info(Slf4jLogger.java:42)
at com.alibaba.dubbo.common.logger.support.FailsafeLogger.info(FailsafeLogger.java:93)
at com.dianwoba.universe.dubbo.filter.ResponseFilter$1.run(ResponseFilter.java:116)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

waiting for monitor entry :说明当前线程正处于EntryList队列中,等待获取监视器锁。

 

说明:Java中synchronized的同步语义主要基于Java对象头和monitor实现,每个monitor同一时间只能由一个线程拥有,其他想要获取该monitor只能等待,其中monitor具有两个队列:WaitSet 和 EntryList。当某个线程在拥有monitor时,调用了Object.wait(),则会释放monitor,进入WaitSet等待,等待其他线程调用Object的notify()/notifyAll()来唤醒,此时将会重新竞争monitor,此时线程状态为WAITING,WaitSet 中等待的状态是 “in Object.wait()”;当某个线程尝试进入synchronized代码块或方法时,获取monitor失败则会进入EntryList队列,此时线程状态为BLOCKED,EntryList中等待的状态为“waiting for monitor entry”。

 

根据jstack日志,有377个dubbo线程在等待锁定资源“0x0000000085057998”,从堆栈可知,这些线程都在竞争RollingRandomAccessFileManager的monitor,让我们看看那个线程拥有了该监视器,看日志:

"DubboServerHandler-192.168.10.33:33180-thread-429" #553 daemon prio=5 os_prio=0 tid=0x00007f339c09f800 nid=0x4467 waiting for monitor entry [0x00007f331f53a000]
java.lang.Thread.State: BLOCKED (on object monitor)
at org.apache.logging.log4j.core.appender.rolling.RollingFileManager.checkRollover(RollingFileManager.java:149)
- locked <0x0000000085057998> (a org.apache.logging.log4j.core.appender.rolling.RollingRandomAccessFileManager)
at org.apache.logging.log4j.core.appender.RollingRandomAccessFileAppender.append(RollingRandomAccessFileAppender.java:88)
at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:155)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:128)
at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:119)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:390)
at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:375)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:359)
at org.apache.logging.log4j.core.config.LoggerConfig.logParent(LoggerConfig.java:381)
at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:376)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:359)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:349)
at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:63)
at org.apache.logging.log4j.core.Logger.logMessage(Logger.java:146)
at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:1993)
at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1852)
at org.apache.logging.slf4j.Log4jLogger.warn(Log4jLogger.java:239)
at com.alibaba.dubbo.common.logger.slf4j.Slf4jLogger.warn(Slf4jLogger.java:54)
at com.alibaba.dubbo.common.logger.support.FailsafeLogger.warn(FailsafeLogger.java:107)
at com.alibaba.dubbo.rpc.filter.TimeoutFilter.invoke(TimeoutFilter.java:48)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.protocol.dubbo.filter.TraceFilter.invoke(TraceFilter.java:78)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.ContextFilter.invoke(ContextFilter.java:60)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:112)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:38)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:38)
at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)
at com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:108)
at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:84)
at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:170)
at com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:52)
at com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:82)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

看到该线程的堆栈就一脸懵b了,它已经锁定了资源“0x0000000085057998”,但仍然处于BLOCKED状态,是不是有死锁的味道?但是这里不是死锁,最可能的原因是:

线程没有获得运行所需的资源;
JVM正在进行fullGC

从这部分日志可知,大部分线程阻塞在打印监控日志的过程中,所以很多请求出现超时。主要原因CPU占用率高,持有锁的线程处理过程非常慢,导致越来越多的线程在锁竞争中被阻塞,整体性能下降。

 

到此,仍然没有找到问题的原因,再一次观察资源占用情况,发现当出现问题时,内存占用持续增长,且无下降痕迹,然后找运维dump了一份GC日志,发现JVM一直在做fullGC,而每次GC之后内存基本没变化,说明程序中发生了内存泄漏。最后定位到发生内存泄漏的地方是一个分页查询接口,SQL语句中漏掉了limit,offset。

 

这尼玛一次性将整张表的数据查出来(300万),还要对300万记录循环处理一遍,这内存不爆掉就怪了。正是因为该原因,导致内存长时间没有释放,JVM执行fullGC无法回收内存,导致持续做fullGC,CPU被耗尽,无法处理应用请求。

 

综上,罪魁祸首是发生了内存泄漏,导致CPU突然飙升,Dubbo活动线程增大,请求处理超时。根据以上分析,同时也暴露了另外一个不合理的问题:dubbo线程池数量配置过大,最大值为1500,也就是说最终线程池中会有1500个线程来处理用户请求,当并发量高时,活动线程数增加,CPU频繁进行上下文切换,系统的吞吐率并不会太高。

 

本文记录该过程,一方面是为了记录曾经踩过的坑,同时提高自己的故障分析和处理能力。当需要问题时,一定不要着急,学会分析问题,找到问题所在。尤其是遇到线上问题时,由于无法调试,一定要在应用中做监控,当出现问题时,一定要结合日志来分析,业务中的问题结合业务日志,性能问题结合内存dump日志和线程dump日志等等。

7、jstack 84204 >> log.log（将进程号位84204的堆栈运行信息输入到log.log日志文件夹中）

生产文件的位置在当前文件夹中