Jstack命令

官方解释

jstack prints Java stack traces of Java threads for a given Java process or core file or a remote debug server. For each Java frame, the full class name, method name, ‘bci’ (byte code index) and line number, if available, are printed. With the -m option, jstack prints both Java and native frames of all threads along with the ‘pc’ (program counter). For each native frame, the closest native symbol to ‘pc’, if available, is printed.

OPTIONS

• -F
  Force a stack dump when ‘jstack [-l] pid’ does not respond.
• -l
  Long listing. Prints additional information about locks such as list of owned java.util.concurrent ownable synchronizers.
• -m
  prints mixed mode (both Java and native C/C++ frames) stack trace.
• -h
  prints a help message.
• -help
  prints a help message

以上为oracle官方对jstack命令的简介和使用说明

https://docs.oracle.com/javase/7/docs/technotes/tools/share/jstack.html

从上面的信息可以得 Jstack主要用来查看某个Java进程内的线程堆栈信息

使用jstack定位运行时异常 ⭐️⭐️⭐️

当Java程序运行时出现异常，我们可以使用jstack命令来定位和分析具体问题。

下面简单介绍一下如何使用jstack定位到具体的出错的位置

共5个步骤：

1. jps 查看java进程pid
2. top -Hp pid 找出该进程内最耗费CPU的线程
3. printf “%x\n” 1787 得到十六进制值为6fb
4. jstack pid > file.log 通过jstack 把该进程的所有线程堆栈打印到file.log中
5. vi file.log 打开文件搜索 6fb 找到具体出问题的代码

补充

1. 如果服务是docker部署的方式

找到docker服务的pid

docker ps

进入docker

docker exec -it {
    
    pid} /bin/bash

再使用Jstack命令

2. jstack统计线程数

/opt/java8/bin/jstack -l 28367 | grep 'java.lang.Thread.State' | wc -l