The second part, debug arthas code running in the target JVM, this is the part that developers care about.

1. Start Demo in debug mode

   Write a simple java Demo:

   import java.util.concurrent.TimeUnit;
   import java.util.concurrent.atomic.AtomicInteger;
   public class Demo {
       static class Counter {
           private static AtomicInteger count = new AtomicInteger(0);
           public static void increment() {
               count.incrementAndGet();
           }
           public static int value() {
               return count.get();
           }
       }
   
       public static void main(String[] args) throws InterruptedException {
           while (true) {
               Counter.increment();
               System.out.println("counter: " + Counter.value());
               TimeUnit.SECONDS.sleep(1);
           }
       }
   }

   Complie and start:

   javac Demo.java
   java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=8000 Demo
   

2. IDEA add new remote configuration

   

3. Add breakpoint at com.taobao.arthas.agent.AgentBootstrap#agentmain, then start debugging

   

4. Run as.sh to attach to the Demo jvm

   $ ./as.sh
   Arthas script version: 3.0.4
   Found existing java process, please choose one and hit RETURN.
   * [1]: 59234 Demo
   [2]: 56707 org.jetbrains.idea.maven.server.RemoteMavenServer
   [3]: 56612
   [4]: 442
   
   Calculating attach execution time...
   Attaching to 59234 using version 3.0.5.20180927185309...

5. IDEA stop at breakpoint

   

Nice , :-)

@hengyunabc This is pretty readable now. Thanks for the help.

But still there is an issue about the first part debugging Arthas core.

1. booting Arthas via JPDA_SUSPEND=y bin/as.sh debug;
2. configuring arthas remote;
3. starting via debug.

Indeed it will stop at the arthas.main and I can check the attachAgent details, but still after this (attaching the arthas agent), the arthas remote will be disconnected as:

Connected to the target VM, address: 'localhost:8888', transport: 'socket'
Disconnected from the target VM, address: 'localhost:8888', transport: 'socket'

I can NOT still debug the command implementation in arthas core as hoped.

Like tt -D

@ralf0131 Please help me out if anything I missed out.

I think I got the point now as for #222 (comment)

the second part is actually used to debug the arthas.core commands.

I will update the https://github.com/alibaba/arthas/blob/master/CONTRIBUTING.md to make it easier for other contributors. @hengyunabc Sounds okay?

IDEA remete debug -> IDEA remote debug

@shentuUrey Thanks, fixed.

@Hearen In the second part,i encounter a problem that can not debug the arthas.core commands.Can u tell me how did u solve it？just like 'help' ,i don't debug in HelpCommand.

Debug arthas-boot.jar

arthas-boot.jar is a normal java application. If you want to debug it, just start to debug it in IDE.

You can also start it with remote debugging arguments: java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=8000 -jar arthas-boot.jar

Debug arthas-boot.jar

arthas-boot.jar is a normal java application. If you want to debug it, just start to debug it in IDE.

You can also start it with remote debugging arguments: java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=8000 -jar arthas-boot.jar

thank you @hengyunabc
both of the ways work.
but the first way can't send ctrl+c signal to embedded terminal(in intellij idea).
the second way works well for me!

Debug arthas-boot.jar

arthas-boot.jar is a normal java application. If you want to debug it, just start to debug it in IDE.

You can also start it with remote debugging arguments: java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=8000 -jar arthas-boot.jar

Thank you!

如果在第二部分的调试过程中，出现了如下问题

可以启动as.sh，然后shutdown，重启arthas之后再试。

成功之后的样子

the way like this (Hearen#20) is ok.