RFR: JDK-8173180 VirtualMachine.startLocalManagementAgent() returns URI with unreliable IP address

[Daniel Fuchs]

On 20/06/2017 12:42, Ujwal Vangapally wrote:
> Thanks for the Review Daniel, Harsha.
> 
> Yes with this fix JConsole running on JDK 8 won't be able to connect to 
> a process running on higher version of Java containing this change.
> 
> I think even Harsha is agreeing this, his point is that the use case 
> where a client running on JDK 8 trying to connect to a process running 
> on latest releases is rare. As mostly for Local Management both client 
> and server will be running on same machine using same JDK for starting 
> both client and server .
> 
> please correct me if this is not the case.

Well - I believe it could be quite common to use VisualVM running
on JDK 8 to connect to JDK 9 processes. JMX is all about
interoperability so I'd be very reluctant to break this 'by
default'.

> can we have this fix with interoperability issue between versions ?

Maybe you could make the fix conditional to a system property being
defined? Also are you sure what you are proposing is the correct fix
for this issue?

Note that - if I'm not mistaken - you can work around the original issue
by specifying -Djava.rmi.server.hostname=<address> on the command line.
http://docs.oracle.com/javase/8/docs/technotes/guides/rmi/javarmiproperties.html
This will instruct RMI to put the specified <address> inside its stubs.
The inconvenience is that this is global (for all RMI stubs, just not
only those used by JMX) - but would that be an issue for the use case
mentioned in the bug?

best regards,

-- daniel

> 
> Thanks,
> 
> Ujwal.
> 
> 
> 
> On 6/20/2017 2:40 PM, Daniel Fuchs wrote:
>> Hi Harsha,
>>
>> Maybe I'm missing something.
>> How is the local agent started?
>>
>> If it's started when you connect jconsole to a process
>> by specifying the process ID - then I suspect this will
>> prevent e.g. jconsole or jvisualvm running on JDK 8 to
>> connect to your process.
>>
>> Can you verify that it's not the case?
>>
>> best regards,
>>
>> -- daniel
>>
>> On 20/06/2017 09:11, Harsha Wardhana B wrote:
>>> Hi Daniel,
>>>
>>> The fix is applicable only to local JMX agent and the most common use 
>>> case would be client and server running from same JVM.
>>> It is highly unlikely that local JMX agent will be started to cater 
>>> for out-of-jvm clients.
>>>
>>> I don't see how introducing this fix can cause new interoperability 
>>> problems. Can you please elaborate?
>>>
>>> -Harsha
>>>
>>> On Monday 19 June 2017 10:23 PM, Daniel Fuchs wrote:
>>>> Hi,
>>>>
>>>> If I'm not mistaken then this will make it impossible
>>>> for earlier release to interoperate with newer releases
>>>> as the LocalRMIClientSocketFactory class will not be
>>>> present the client tries to deserialize the stub.
>>>>
>>>> best regards,
>>>>
>>>> -- daniel
>>>>
>>>> On 19/06/2017 11:52, Ujwal Vangapally wrote:
>>>>> Hi,
>>>>>
>>>>> Kindly review the fix for bug below
>>>>>
>>>>> https://bugs.openjdk.java.net/browse/JDK-8173180
>>>>>
>>>>> webrev: 
>>>>> http://cr.openjdk.java.net/~uvangapally/webrev/2017/8173180/webrev.00/
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Ujwal
>>>>>
>>>>
>>>
>>
>