RFR: 8263635: Add --prefix option to jhsdb debugd [v2]

[Chris Plummer]

On Tue, 11 May 2021 00:15:21 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> `jhsdb debugd` supports server name prefix with `sun.jvm.hotspot.rmi.serverNamePrefix` system property. It will be used as remote name for SA remote object. It is "SARemoteDebugger" by default.
>> 
>> As a result, remote name will be constructed as following:
>> 
>> 
>> //host[:port]/<serverNamePrefix>['_'<id>]
>> 
>> 
>> However we have no way to set it excepting system property. jhsdb should provide the way to set it as a command line option. And also we should add the way to specify the prefix when we connect to debug server. I will add it like `--connect id at server:1234/prefix`.
>> 
>> I've also filed [CSR for this PR](https://bugs.openjdk.java.net/browse/JDK-8265897). Please review it.
>> This PR modifies DisableRegistryTest.java, but it has been addressed in ProblemList-zgc.txt now. So this PR does not affect ZGC.
>
> Yasumasa Suenaga has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Update jhsdb man page
>  - Merge remote-tracking branch 'upstream/master' into JDK-8263635
>  - Update help message
>  - 8263635: Add --prefix option to jhsdb debugd

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/RMIHelper.java line 93:

> 91: 
> 92:     public static Remote lookup(String debugServerID) throws DebuggerException {
> 93:         // debugServerID follows the pattern [unique_id@]host[:port][/prefix]

It's a bit unclear to me why we need both a "unique_id" and a "prefix". I understand that the SA already append the two, and that previously the prefix was a constant, but I don't see why the user would ever need to set the "prefix" when they can always specify a "unique_id" that is truly unique. What is the use case for this?

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PR: https://git.openjdk.java.net/jdk/pull/3669