RFR: 8262520: Add CLHSDB command to connect to debug server

[Yasumasa Suenaga]

On Tue, 2 Mar 2021 11:39:10 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

>>> @plummercj Ok, I try to add debug server support to `attach` clhsdb command. Then should we still need CSR?
>> 
>> Pushed new commit to be implemented as `attach`. It works fine with serviceability/sa jtreg tests on my Linux x64.
>> I will add CSR if you are ok.
>
> Hi,
> I ran the first version and agree it works, the connect command worked OK when I ran a local, manual test.  But I do like adding to the attach Command rather than connect, avoiding introducing a new Command name.
> 
> Assuming an int is a PID like in Tool.java is reasonable.  
> You can have a leading numeral since a certain RFC, but although I can't find clear language to say it's definitely illegal, actualy using a fully numeric hostname seems unwise.
> 
> CLHSDB.java line 185
> Now that "private void attachDebugger(int pid)" takes an int, we don't want to catch NumberFormatException, that try/catch block is not wanted.
> 
> In the testcase, I think it will fail if a command throws an Exception, but that is limiting what problems it can detect:
> could we make the test check at least some of the key output to show that we are attached and getting information, not errors or something unexpected?  If at least some key commands we issue are checked that they contain some output indicating success that would be great.

Thanks @kevinjwalls !

> CLHSDB.java line 185
> Now that "private void attachDebugger(int pid)" takes an int, we don't want to catch NumberFormatException, that try/catch block is not wanted.

I fixed it in new commit, and also I fixed HSDB.java.

> In the testcase, I think it will fail if a command throws an Exception, but that is limiting what problems it can detect:
> could we make the test check at least some of the key output to show that we are attached and getting information, not errors or something unexpected? If at least some key commands we issue are checked that they contain some output indicating success that would be great.

I added calling `class java.lang.Object` and `class java.lang.String` in testcase. We can check whether the connection works fine through them.

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PR: https://git.openjdk.java.net/jdk/pull/2773