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

[Yasumasa Suenaga]

On Wed, 12 May 2021 23:03:04 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> "prefix" is similar to "unique_id" as you said, but it is useful to group debugees.
>> 
>> For example, the host runs 2 container pods as following:
>> 
>> * Pod A
>>     * Container 1
>>     * Container 2
>>     * Container 3
>> * Pod B
>>     * Container 1
>>     * Container 2
>>     * Container 3
>> 
>> If we want to compare 2 pods with jhsdb, we can set ID like "A-1", "B-1".
>> However, if the prefix is supported on jhsdb, we can set ID and prefix like "1 at localhost/A", "1 at localhost/B". I think it is easy to understand.
>
> Ok, this explanation seems reasonable, but is not something that is really conveyed with the the name `--prefix` or with the help "Sets the prefix to distinguish SA debugee". We are at the same giving too much and too little info. Too much in that we are saying that it is a prefix of some sort, which then leads to that fact that we don't explain how it is used in the RMI URL.
> 
> I'm not saying that we need to explain how  the `--connect [<id>@]<host>[:registryport][/prefix]` option is converted into an RMI URL (although perhaps we should), but it seems we at least need to describe the relation between `<id>` and `/prefix`. Otherwise no one is really going to understand how/why to use it.
> 
> Also, having the prefix at the end of the "serverID" string seems odd. Maybe it should be:
> 
>    [[prefix/]unique_id@]host[:port]

Finally, all parameters will be transformed to `//host[:port]/<serverNamePrefix>['_'<unique_id>]`.
`--prefix` and `id` affect to RMI object name to be precise. So ID is object name, then the prefix will be added to it.

Based on them, how about this?


--prefix <url prefix> Set the prefix to add to debug server instance name.


I understand is is odd the value is added to the tail even if it is named "prefix".
Both `prefix` and `id` are optional, so we can specify `prefix` only, then `prefix/@host` is strange for me.

How about this pattern? Use ":" instead of "/" like a URL.


[prefix:][unique_id@]host[:port]


I thought to give new name instead of "prefix", but I give up because I have not good idea and would be inconsistent system property. (`sun.jvm.hotspot.rmi.serverNamePrefix`)

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