Java|Java 定位导致CPU飙升的代码过程 Java定位导致CPU飙升的代码过程

线上的一个日志实时输出的程序曾经出过这样一个问题，刚开始上线java程序占用的CPU的资源很少,但是到了整点的时候,CPU直线飙高，直接到达100%根本没有要下降的趋势，唯一的方法只能杀掉它了，后面在借助jstack与top排查到线程然后定位到某行代码出的问题。

排查演示

使用jps找到程序的pid

[root@logs bin]# ./jps -l -m | grep logdir2 22169 galaxy-log-online-0.1-SNAPSHOT-all.jar 3002 /logdir2

找到22169进程ID
找到CPU过高的线程

top -H -p 22169top - 19:03:22 up 156 days,5:57,4 users,load average: 1.00, 2.84, 4.25 Threads:15 total,0 running,15 sleeping,0 stopped,0 zombie %Cpu(s): 99.4 us, 12.6 sy,0.0 ni, 62.6 id,4.8 wa,0.0 hi,2.6 si,0.0 st KiB Mem :8010456 total,206760 free,1079668 used,6724028 buff/cache KiB Swap:0 total,0 free,0 used.6561460 avail MemPID USERPRNIVIRTRESSHR S %CPU %MEMTIME+ COMMAND 22184 root200 45433567414812960 S80.040.90:19.96 java 22169 root200 45433567414812960 S0.00.90:00.00 java 22170 root200 45433567414812960 S0.00.90:00.35 java 22171 root200 45433567414812960 S0.00.90:00.08 java 22172 root200 45433567414812960 S0.00.90:00.09 java ...

将线程转为16进制

[root@logs bin]# printf "%x" 22184 56a8

使用jstack定位到线程

[root@logs bin]# ./jstack 22169 | grep 56a8 "Thread-1" #9 prio=5 os_prio=0 tid=0x00007fe428230800 nid=0x56a8 waiting on condition [0x00007fe4121a5000]

使用3D肉眼来查看线程运行的代码了

"Thread-1" #9 prio=5 os_prio=0 tid=0x00007fe428230800 nid=0x56a8 waiting on condition [0x00007fe4121a5000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at java.lang.Thread.sleep(Unknown Source) at java.util.concurrent.TimeUnit.sleep(Unknown Source) at com.dounine.tool.http.sql.LogsRequest$4.run(LogsRequest.java:152) at java.lang.Thread.run(Unknown Source)

【Java|Java 定位导致CPU飙升的代码过程】然后开始从LogsRequest.java152行开始找起，发现里面有一个死循环...
FIX 它然后开开心心下班