RFR: JDK-8187498: Add a -Xmanagement flag as syntactic sugar for -Dcom.sun.management.jmxremote.* properties

[Harsha Wardhana B]

Hi,

Below is the updated webrev.

http://cr.openjdk.java.net/~hb/8187498/webrev.03/


On Wednesday 14 February 2018 01:15 AM, mandy chung wrote:
>
>
> On 2/13/18 1:30 AM, Harsha Wardhana B wrote:
>> Hi,
>>
>> Please find below the revised webrev.
>>
>> http://cr.openjdk.java.net/~hb/8187498/webrev.02/
>>
>>
>> On Friday 09 February 2018 05:07 AM, mandy chung wrote:
>>> On 2/7/18 1:19 AM, Harsha Wardhana B wrote:
>>> > 
>>> > --start-management-agent will not be recognized in the current format and
>>> > hence will not default to --start-management-agent=local=true.
>>>
>>> `--start-local-management-server` is one option as Alan suggests.
>>> Another option is to make `--start-management-agent` to accept
>>> an optional argument.  VM can accept `--start-management-agent`
>>> or `--start-management-agent=port=1234,ssl=on`.  It may require
>>> more launcher change to support it.
>> Yes. It requires lot more changes to launcher. Hence optional 
>> argument to --start-management-agent was not added in order to keep 
>> the launcher impact minimum.
>
> This is just one option for you to consider.   So the current proposal 
> of the new option to start a remote management server, right?
Not necessarily. --start-management-agent=local=true starts local server 
and --start-management-agent=port=1234 starts remote management server.
>>> Agent.java
>>>   If --start-management-agent is set, -Dcom.sun.management.* takes
>>>   precedence.  Do you really want to do that?  The new VM option
>>>   intends to simplify the command-line to type in.  I think it's
>>>   cleaner and reasonable if --start-management-agent is specified,
>>>   -Dcom.sun.management.* are ignored (maybe worth emit a warning if set)
>> We can probably document that -D options will be overridden instead 
>> of emitting a warning.
>
> What is the behavior when -Dcom.sun.management.jmxremote.port=1234 
> --start-management-agent port=2345 
> -Dcom.sun.management.jmxremote.port=3456?
>
> What is the value of the system property 
> com.sun.management.jmxremote.port at runtime?  What port number does 
> the management server start with?
As said earlier, values set via new flags override values set by -D 
flags. So 2345 will be the value of com.sun.management.jmxremote.port. 
Added a test case to validate that.
>
>>>   The implementation uses VMManagement::getVmArguments and scan
>>>   the VM options for -start-management-agent.  The VM is the one
>>>   invoking jdk.internal.agent.Agent::startAgent.  A simpler option
>>>   is to change Agent::startAgent to take an argument parameter
>>>   that will be passed with the argument of --start-management-agent
>>>   or null if not set.
>>>
>>>   Similarly for startRemoteManagementAgent and startLocalAgent_name.
>> Implementing this change requires lot of changes to argument parsing 
>> in native code and hence it is simpler to handle this at java layer.
>
> Can you describe how --start-management-agent option will be used for 
> jcmd and any other tool that attaches to a running VM to start the 
> agent?  Example command-line will be useful.
--start-management-agent cannot be used by jcmd (or dynamic attach) as 
it accepts flags only in -D format or -D flags with com.sun.management 
removed. That code to parse string passed via jcmd was a mistake and 
hence I have removed it.
>
>
> Mandy
-Harsha
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