Ubuntu 20.10官方源安装OpenJDK 8u292、Tomcat9的无法Attach

[phith0n]

环境信息

• arthas-boot.jar 或者 as.sh 的版本： 3.5.0
• Arthas 版本: 3.5.0
• 操作系统版本: Ubuntu 20.10
• 目标进程的JVM版本: 1.8.0_292
• 执行arthas-boot的版本: 1.8.0_292

重现问题的步骤

纯净的Ubuntu 20.10系统，安装OpenJDK8和Tomcat9：

apt update
apt install openjdk-8-jdk tomcat9 tomcat9-examples

当前Java版本为：

tomcat@sample-jvm:/tmp/arthas$ java -version
openjdk version "1.8.0_292"
OpenJDK Runtime Environment (build 1.8.0_292-8u292-b10-0ubuntu1~20.10-b10)
OpenJDK 64-Bit Server VM (build 25.292-b10, mixed mode)

此时，tomcat9以tomcat用户运行，PID号是7391：

sample@sample-jvm:~$ ps aux|grep tomcat
tomcat      7391  0.6  4.0 5536164 329780 ?      Ssl  22:48   0:08 /usr/lib/jvm/java-8-openjdk-amd64/bin/java -Djava.util.logging.config.file=/var/lib/tomcat9/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.awt.headless=true -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -Dignore.endorsed.dirs= -classpath /usr/share/tomcat9/bin/bootstrap.jar:/usr/share/tomcat9/bin/tomcat-juli.jar -Dcatalina.base=/var/lib/tomcat9 -Dcatalina.home=/usr/share/tomcat9 -Djava.io.tmpdir=/tmp org.apache.catalina.startup.Bootstrap start

然后我们来到/tmp目录，切换到tomcat用户，并创建arthas目录，下载arthas-boot（3.5.0）：

root@sample-jvm:/tmp# su -l tomcat -s /bin/bash
tomcat@sample-jvm:/$ id
uid=997(tomcat) gid=997(tomcat) groups=997(tomcat)
tomcat@sample-jvm:/$ mkdir /tmp/arthas
tomcat@sample-jvm:/$ cd /tmp/arthas/
tomcat@sample-jvm:/tmp/arthas$ curl -O https://arthas.aliyun.com/arthas-boot.jar
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  137k  100  137k    0     0   814k      0 --:--:-- --:--:-- --:--:--  814k
tomcat@sample-jvm:/tmp/arthas$ ls
arthas-boot.jar

然后执行arthas-boot，对进程7391进行attach，失败：

tomcat@sample-jvm:/tmp/arthas$ java -jar arthas-boot.jar 7391
[INFO] arthas-boot version: 3.5.0
[INFO] Start download arthas from remote server: https://arthas.aliyun.com/download/3.5.0?mirror=center
[INFO] File size: 12.22 MB, downloaded size: 1.76 MB, downloading ...
[INFO] File size: 12.22 MB, downloaded size: 6.78 MB, downloading ...
[INFO] Download arthas success.
[INFO] arthas home: /tmp/.arthas/lib/3.5.0/arthas
[INFO] Try to attach process 7391
[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:63)
	at com.sun.tools.attach.VirtualMachine.attach(VirtualMachine.java:208)
	at com.taobao.arthas.core.Arthas.attachAgent(Arthas.java:97)
	at com.taobao.arthas.core.Arthas.<init>(Arthas.java:26)
	at com.taobao.arthas.core.Arthas.main(Arthas.java:137)
[ERROR] attach fail, targetPid: 7391

期望的结果

成功attach。

实际运行的结果

tomcat@sample-jvm:/tmp/arthas$ java -jar arthas-boot.jar 7391
[INFO] arthas-boot version: 3.5.0
[INFO] Start download arthas from remote server: https://arthas.aliyun.com/download/3.5.0?mirror=center
[INFO] File size: 12.22 MB, downloaded size: 1.76 MB, downloading ...
[INFO] File size: 12.22 MB, downloaded size: 6.78 MB, downloading ...
[INFO] Download arthas success.
[INFO] arthas home: /tmp/.arthas/lib/3.5.0/arthas
[INFO] Try to attach process 7391
[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:63)
	at com.sun.tools.attach.VirtualMachine.attach(VirtualMachine.java:208)
	at com.taobao.arthas.core.Arthas.attachAgent(Arthas.java:97)
	at com.taobao.arthas.core.Arthas.<init>(Arthas.java:26)
	at com.taobao.arthas.core.Arthas.main(Arthas.java:137)
[ERROR] attach fail, targetPid: 7391

[hengyunabc]

https://arthas.aliyun.com/doc/faq.html#target-process-not-responding-or-hotspot-vm-not-loaded

[phith0n]

https://arthas.aliyun.com/doc/faq.html#target-process-not-responding-or-hotspot-vm-not-loaded

您好，我按照FAQ中的步骤进行排查：

1. 已切换到tomcat用户执行，细节可以参见我的issue描述
2. 执行jstack出现下面错误：

tomcat@sample-jvm:/tmp/sample$ jstack -l 874
874: Unable to open socket file: target process not responding or HotSpot VM not loaded
The -F option can be used when the target process is not responding

不太明白假死是什么意思，但是我是本地虚拟机里测试环境，仅安装了源里的Tomcat，无其他用户访问。我正常访问Tomcat页面是没有问题的，JSP也能正常执行。

3. 尚未进行尝试，等下尝试再回复。但是我还是更想知道tomcat进程无法attach的原因。
4. issue中貌似没有我遇到的问题

感谢回复！

[phith0n]

测试了一下math-game，是可以成功attach的。不过我希望能找到无法Attach Tomcat的原因，看看是否有同样遭遇的同学。

我的问题可以复现，刚才临时下载的Ubuntu 20.10 Server版本并安装，安装好以后没干任何事，就是按照issue中的步骤进行了测试，排除了一下大部分干扰因素。:)

[jiaozg22]

centos7下openjdk也失败

[ilaotan]

可以反着试试oracle jdk8, 我们公司项目在oraclejdk下正常, openjdk 总会出莫名的错误没法使用

[virusdefender]

应该和 systemd 有关系。

apt 安装 tomcat 是由 systemd 拉起来 java 的，而 systemd 给 java 加了一些安全配置，包括 PrivateTmp AmbientCapabilities ProtectSystem，去掉这三个之后执行 sudo systemctl daemon-reload && sudo systemctl restart tomcat9 就可以工作了，详见 /lib/systemd/system/tomcat9.service。

具体原因暂时还没研究。

https://bugs.launchpad.net/ubuntu/+source/tomcat9/+bug/1981523