不停机还能替换代码?6年的 Java程序员表示不可思议

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相信很多人都有这样一种感受,自己写的代码在开发、测试环境跑的稳得一笔,可一到线上就抽风,不是缺这个就是少那个反正就是一顿报错,而线上调试代码又很麻烦,让人头疼得很。不过, 阿里巴巴出了一款名叫Arthas的工具,可以在线分析诊断Java代码,让人眼前一亮。

Arthas 是什么?

Arthas(阿尔萨斯) 是阿里开源的一个Java在线分析诊断工具。

Arthas 能解决啥问题?

在日常开发上线过程中,我们多多少少都会遇到下边这些问题,苦于无法在线调试,只能通过老鸟的经验来硬分析bug,效率上不去还总开口问别人答疑解惑,多少有些不好意思

  • 这个类从哪个 jar 包加载的?为什么会报各种类相关的 Exception?

  • 我改的代码为什么没有执行到?难道是我没 commit?分支搞错了?

  • 遇到问题无法在线上 debug,难道只能通过加日志再重新发布吗?

  • 线上遇到某个用户的数据处理有问题,但线上同样无法 debug,线下无法重现!

  • 是否有一个全局视角来查看系统的运行状况?

  • 有什么办法可以监控到JVM的实时运行状态?

  • 线上代码有错误,不想重新发布?那能不能改class文件替换一下?

Arthas两种安装、启动方式

1、jar包启动

wget https://alibaba.github.io/arthas/arthas-boot.jar

java -jar arthas-boot.jar --target-ip 0.0.0.0

首先想用arthas调试项目,服务器必须要有运行着的Java服务,demo-0.0.1-SNAPSHOT.jar就是我启动的测试项目,启动arthas后它会自动检测本地所有的Java服务列出来,我们只需按照序号输入想要调试的项目即可,选1进入对应进程的arthas交互平台

[root@iz2zehzeir87zi8q99krk1z data]# java -jar arthas-boot.jar   --target-ip 172.17.72.201
[INFO] arthas-boot version: 3.1.0
[INFO] Found existing java process, please choose one and hit RETURN.
* [1]: 28679 demo-0.0.1-SNAPSHOT.jar

2、在线安装

curl -L https://alibaba.github.io/arthas/install.sh | sh

执行上面的命令会在所在的文件中生成as.sh执行文件 在这里插入图片描述 启动arthas

./as.sh PID #进程id 指定JAVA进程id
./as.sh -h #h来获取更多参数信息

3、远程连接:

要想使用arthas服务的 web console必须对外暴露本机ip

java -jar arthas-boot.jar --target-ip 172.17.72.201
java -jar arthas-boot.jar --telnet-port 9999 --http-port -1
./as.sh --target-ip 0.0.0.0
./as.sh --telnet-port 9999 --http-port -1

访问arthas控制台也有两种方法

(1)、web console 界面

重点说明:--target-ipip 一定要是arthas所在机器对外暴露的ip,但如果用的是阿里云机器必须要使用私有ip启动arthas服务,但访问必须是公网IP 在这里插入图片描述

(2)、telnet方式

telnet 10.0.2.5 8563

在这里插入图片描述 访问 http://59.110.218.9:8563/ ,进入交互平台 在这里插入图片描述

Arthas 命令使用

1、Dashboard 命令

查看当前系统的实时数据面板,例如:服务器thread信息、内存memory、GC回收等情况 在这里插入图片描述

2、Thread(线程监控)

$ thread -n 3
"as-command-execute-daemon" Id=57 cpuUsage=72% RUNNABLE
    at sun.management.ThreadImpl.dumpThreads0(Native Method)
    at sun.management.ThreadImpl.getThreadInfo(ThreadImpl.java:448)
    at com.taobao.arthas.core.command.monitor200.ThreadCommand.processTopBusyThreads(ThreadCommand.java:133)
    at com.taobao.arthas.core.command.monitor200.ThreadCommand.process(ThreadCommand.java:79)
    at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl.process(AnnotatedCommandImpl.java:82)
    at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl.access$100(AnnotatedCommandImpl.java:18)
    at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl$ProcessHandler.handle(AnnotatedCommandImpl.java:111)
    at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl$ProcessHandler.handle(AnnotatedCommandImpl.java:108)
    at com.taobao.arthas.core.shell.system.impl.ProcessImpl$CommandProcessTask.run(ProcessImpl.java:370)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

    Number of locked synchronizers = 1 
    - java.util.concurrent.ThreadPoolExecutor$Worker@a2f70c7

可以看到这个线程是被synchroned关键字锁导致的阻塞 ,目前只支持找出synchronized关键字阻塞住的线程, 如果是java.util.concurrent.Lock, 目前还不支持。

Number of locked synchronizers = 1
    - java.util.concurrent.ThreadPoolExecutor$Worker@a2f70c7
thread -n 3 #当前最忙的前N个线程
thread -b, ##找出当前阻塞其他线程的线程
thread -n 3 -i 1000 #间隔一定时间后展示

重点学习thread -b, ##找出当前阻塞其他线程的线程

3、JVM (jvm实时运行状态,内存使用情况等)

$ jvm
 RUNTIME                                                                                                                                                                                                                                    
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 MACHINE-NAME                                                       28679@iz2zehzeir87zi8q99krk1z                                                                                                                                           
 JVM-START-TIME                                                     2019-03-28 17:32:16                                                                                                                                                     
 MANAGEMENT-SPEC-VERSION                                            1.2                                                                                                                                                                     
 SPEC-NAME                                                          Java Virtual Machine Specification                                                                                                                                      
 SPEC-VENDOR                                                        Oracle Corporation                                                                                                                                                      
 SPEC-VERSION                                                       1.8                                                                                                                                                                     
 VM-NAME                                                            Java HotSpot(TM) 64-Bit Server VM                                                                                                                                       
 VM-VENDOR                                                          Oracle Corporation                                                                                                                                                      
 VM-VERSION                                                         25.191-b12                                                                                                                                                              
 INPUT-ARGUMENTS                                                    []                                                                                                                                                                      
 CLASS-PATH                                                         demo-0.0.1-SNAPSHOT.jar                                                                                                                                                 
 BOOT-CLASS-PATH                                                    /usr/local/jdk/jre/lib/resources.jar:/usr/local/jdk/jre/lib/rt.jar:/usr/local/jdk/jre/lib/sunrsasign.jar:/usr/local/jdk/jre/lib/jsse.jar:/usr/local/jdk/jre/lib/jce.jar 
                                                                    :/usr/local/jdk/jre/lib/charsets.jar:/usr/local/jdk/jre/lib/jfr.jar:/usr/local/jdk/jre/classes                                                                          
 LIBRARY-PATH                                                       /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib       

4、trace (当前方法内部调用路径,路径上每个节点的耗时)

$ trace #类名  #方法名 

在这里插入图片描述 对于执行耗时相对较长的方法,调用链路耗时属性会高亮显示方便排查 在这里插入图片描述

参数 -j 可以过滤jdk的函数 trace -j com.example.demo.controller index2 参数 #cost 可以按执行耗时毫秒ms过滤 trace -j com.example.demo.controller index2 ’#cost >10‘

5、watch

当前方法执行数据观测,能观察到的范围为:返回值、抛出异常、入参

$ trace #类名  #方法名 "{params,target,returnObj,throwExp }" 
OGNL 表达式 {params,target,returnObj,throwExp }

throwExp:异常 params :入参(数组),单个参数params【0】 returnObj:返回值

$ watch com.example.demo.controller index2 "{params,target,returnObj}" -x 5
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 81 ms.
ts
=2019-03-29 14:24:14; [cost=1000.746582ms] result=@ArrayList[
    @Object[][
        @String[辛志富],
    ],
    @controller[
    ],
    @String[index2],
]

6、stack

当前方法被调用的路径,显示当前方法被那些方法调用

public static String uuidOne() {
    return uuidTwo();
}
public static String uuidTwo() {
    return UUID.randomUUID().toString().replaceAll("-""");
}
$ stack  com.example.demo.controller uuidTwo
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 58 ms.
ts
=2019-03-29 14:38:19;thread_name=http-nio-8888-exec-5;id=13;is_daemon=true;priority=5;TCCL=org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader@525b461a
    @com.example.demo.controller.uuidOne()
        at com.example.demo.controller.index2(controller.java:31)
        at sun.reflect.GeneratedMethodAccessor36.invoke(null:-1)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

7、monitor 命令

监控类、方法的调用进行监控,调用次数、成功次数、失败次数、平均响应时长、失败率等

$ monitor -c 4 com.example.demo.controller uuidTwo
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 56 ms.
 timestamp            class                        method   total  success  fail  avg-rt(ms)  fail-rate                                                                                                                                     
--------------------------------------------------------------------------------------------------------                                                                                                                                    
 2019-03-29 14:55:40  com.example.demo.controller  uuidTwo  7      7        0     0.18        0.00%      

8、classloader 命令

将JVM中所有的类加载器统计出来,树状展示

$ classloader #每种classloader加载类的个树
 name                                                    numberOfInstances  loadedCountTotal                                                                                                                                                
 org.springframework.boot.loader.LaunchedURLClassLoader  1                  4463                                                                                                                                                            
 com.taobao.arthas.agent.ArthasClassloader               2                  3631                                                                                                                                                            
 BootstrapClassLoader                                    1                  2961                                                                                                                                                            
 java.net.FactoryURLClassLoader                          1                  835                                                                                                                                                             
 sun.misc.Launcher$AppClassLoader                        1                  46                                                                                                                                                              
 sun.reflect.DelegatingClassLoader                       41                 41                                                                                                                                                              
 sun.misc.Launcher$ExtClassLoader                        1                  25                                                                                                                                                              
Affect(row-cnt:7) cost in 7 ms.
$ classloader -t    # 类加载器间的层级关系
+-BootstrapClassLoader                                                                                                                                                                                                                      
+-sun.misc.Launcher$ExtClassLoader@1959f618                                                                                                                                                                                                 
  +-com.taobao.arthas.agent.ArthasClassloader@5fc476c6                                                                                                                                                                                      
  +-com.taobao.arthas.agent.ArthasClassloader@5017e14b                                                                                                                                                                                      
  +-sun.misc.Launcher$AppClassLoader@5c647e05                                                                                                                                                                                               
    +-java.net.FactoryURLClassLoader@4ad317f0                                                                                                                                                                                               
    +-org.springframework.boot.loader.LaunchedURLClassLoader@20ad9418                                                                                                                                                                       
Affect(row-cnt:7) cost in 5 ms

线上代码热更新(动态修改上线项目代码)

手动在代码中抛异常,不停机不重新发包的情况下,修改线上代码 在这里插入图片描述 启动服务也达到我们预期异常 在这里插入图片描述

替换代码的流程:

1、jad命令 将需要更改的文件先进行反编译,保存下来 ,编译器修改

$ jad --source--only com.example.demo.DemoApplication > /data/DemoApplication.java
在这里插入图片描述
在这里插入图片描述

修改完以后需要将类重新加载到JVM

2、SC命令 查找当前类是哪个classLoader加载的

$ sc -d *DemoApplication | grep classLoader

 classLoaderHash   20ad9418 #类加载器  编号     

3、MC命令 用指定的classloader重新将类在内存中编译

$ mc -c 20ad9418 /data/DemoApplication.java -d /data 
Memory compiler output:
/data/com/example/demo/DemoApplication.class

4、redefine命令 将编译后的类加载到JVM

上边编译后的.class文件地址

$ redefine /data/com/example/demo/DemoApplication.class  
redefine success, size1

文件替换后我们再次访问一下程序,发现异常没有了程序已经是我们修改正确后的,class文件替换成功

总结

这样我们就用arthas现实了不停机、不发包替换了生产环境的Java代码,功能确实比较强大,本文只揭开了arthas强大功能的冰山一角,后续将出更详细的文章,方便大家一起学习。

越懒越勤快

arthas的整体功能虽然很强大,但命令行的输入方式让我头疼不已,岁数大了记忆力真的下降严重,而且作为一个贼 TM 懒的程序员,让我去记住如此多的命令和参数,简直是要了老命。又一次因为懒让我勤快起来,我决定做个arthas命令可视化平台。

设计初衷:设计这个平台的初衷很简单,就是让程序员们把更多的精力放在问题的排查上,而不是记那么多枯燥无趣的命令。本身我也不是一个愿意死记硬背的人,觉得脑子里还是应该多放一些有趣、有意义的东西。可能在用惯了命令行的大佬眼里,这个功能比较鸡肋,甚至有点多余,但毕竟像我这样平凡的人更多一些,每天还陷入在重复的工作当中,工作量能减一点就多轻松一点嘛。

目前平台还在持续的开发中,由于平台是自己在维护,开发进度并不客观,平时利用一些碎片时间开发,毕竟不能耽误工作丢了饭碗嘛。不管会不会有人用,我都会一直做下去。

github地址 : https://github.com/chengxy-nds/arthas-web.git

感兴趣的小伙伴可以私信我,让我们一起打造这个有趣的东西吧!

小福利:

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