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List:       openjdk-serviceability-dev
Subject:    Re: RFR: JDK-8173180 VirtualMachine.startLocalManagementAgent() returns URI with unreliable IP addre
From:       Harsha Wardhana B <harsha.wardhana.b () oracle ! com>
Date:       2017-06-20 13:57:59
Message-ID: 07010699-c9fd-697f-e506-4a98e7f0bbd1 () oracle ! com
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Hi Daniel,


On Tuesday 20 June 2017 06:39 PM, Daniel Fuchs wrote:
> 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'.
Agreed.
>
>> 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?
It's more of a workaround than a fix as we don't see any other way to 
fix 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?
We had the same consideration that setting the RMI property will change 
the Interface address for all the stubs which may not be an acceptable 
fix in this case.
One possible fix (enhancement) would be to define a JMX system property 
that will control the Interface address that goes into RMI stubs. If 
that seems like too much work, we can close this issue as 'won't fix' as 
we don't have any acceptable fix.
>
> best regards,
>
> -- daniel

-Harsha
>
>>
>> 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
>>>>>>
>>>>>
>>>>
>>>
>>
>
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