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

[Chris Plummer]

On Thu, 13 May 2021 05:56:00 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> 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`)

I think this is better, but I think better help output is needed. `prefix` has a default and `unique_id` does not. I think both of these need to be mentioned in the help output. Also, if `unique_id` is not specified, then the value of `prefix` is the name of the RMI object, which seems a bit odd because it is suppose to be a prefix to a name, not the entire name.

I think maybe the property name of `sun.jvm.hotspot.rmi.serverNamePrefix` was not a good choice, and is making it harder to come up with good argument names and syntax. If designing this from scratch, I would have called it `sun.jvm.hotspot.rmi.serverName`, and then appending an optional `unique_id` to it would make more sense.

What if instead of `prefix` you used `servername` and possibly also rename `sun.jvm.hotspot.rmi.serverNamePrefix` to `sun.jvm.hotspot.rmi.serverName`, but also keep legacy support in case someone is already using `sun.jvm.hotspot.rmi.serverNamePrefix` and decides to set it?

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