在linux上启动arthas报“Can not find java process”

发生背景

完整报错信息：

[***@localhost ~]$ java -jar arthas-boot.jar
[INFO] JAVA_HOME: /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.222.b03-1.el7.x86_64/jre
[INFO] arthas-boot version: 3.6.9
[INFO] Can not find java process. Try to run `jps` command lists the instrumented Java HotSpot VMs on the target system.
Please select an available pid.

linux环境：

[***@localhost ~]$ cat /etc/centos-release
CentOS Linux release 7.7.1908 (Core)

解决方案

出现这个报错是因为找不到jps命令，我们默认安装的openjdk是不支持jps的，所以需要卸载Open JDK，安装Oracle JDK，步骤如下：

1. 查看已有的openjdk版本

[***@localhost ~]$ rpm -qa|grep jdk
java-1.8.0-openjdk-1.8.0.222.b03-1.el7.x86_64
java-1.7.0-openjdk-1.7.0.221-2.6.18.1.el7.x86_64
java-1.8.0-openjdk-headless-1.8.0.222.b03-1.el7.x86_64
java-1.7.0-openjdk-headless-1.7.0.221-2.6.18.1.el7.x86_64
copy-jdk-configs-3.3-10.el7_5.noarch

2. 卸载openjdk

[***@localhost ~]$ su
Password: 
[root@localhost yuwei]# yum -y remove copy-jdk-configs-3.3-10.el7_5.noarch
...
[root@localhost yuwei]# java -version
bash: java: command not found...

3. 安装jdk
   3.1 将jdk上传到home目录
   3.2 创建jvm目录 mkdir /usr/lib/jvm
   3.3 解压安装包 tar -zxvf ./jdk-8u181-linux-x64.tar.gz -C /usr/lib/jvm
   3.4 编辑环境变量 vi ~/.bashrc
   3.5 文件最下面添加

   export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_181
   export JRE_HOME=${JAVA_HOME}/jre  
   export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  
   export PATH=${JAVA_HOME}/bin:$PATH
   

   3.6 刷新配置文件，查看版本

   [root@localhost ~]# source ~/.bashrc
   [root@localhost ~]# java -version
   java version "1.8.0_181"
   Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
   Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)
   

4. 最后重启jar看效果

[root@localhost ***]# java -jar arthas-boot.jar 
[INFO] JAVA_HOME: /usr/lib/jvm/jdk1.8.0_181/jre
[INFO] arthas-boot version: 3.6.9
[INFO] Found existing java process, please choose one and input the serial number of the process, eg : 1. Then hit ENTER.
* [1]: 3137 math-game.jar

5. 继续报错

[INFO] File size: 17.83 MB, downloaded size: 17.81 MB, downloading ...
[INFO] Download arthas success.
[INFO] arthas home: /root/.arthas/lib/3.6.9/arthas
[INFO] Try to attach process 3137
Picked up JAVA_TOOL_OPTIONS: 
[ERROR] Start arthas failed, exception stack trace: 
com.sun.tools.attach.AttachNotSupportedException: Unable to open socket file: target process not responding or HotSpot VM not loaded
	at sun.tools.attach.LinuxVirtualMachine.<init>(LinuxVirtualMachine.java:106)
	at sun.tools.attach.LinuxAttachProvider.attachVirtualMachine(LinuxAttachProvider.java:78)
	at com.sun.tools.attach.VirtualMachine.attach(VirtualMachine.java:250)
	at com.taobao.arthas.core.Arthas.attachAgent(Arthas.java:102)
	at com.taobao.arthas.core.Arthas.<init>(Arthas.java:27)
	at com.taobao.arthas.core.Arthas.main(Arthas.java:161)
[ERROR] attach fail, targetPid: 3137

切换用户，arthas程序和应用程序需要在同一个用户账号下，app应用程序是普通用户，当前在root用户下执行的arthas，所以报错。

启动成功，效果图