RFR 8035395: sun/management/jmxremote/startstop/JMXStartStopTest.java fails intermittently: Port already in use

[shanliang]

Jaroslav Bachorik wrote:
> Hi Shanliang,
>
> On 20.2.2014 19:20, shanliang wrote:
>> Jaroslav,
>>
>> The failed tests were:
>>     1, 7, 8, 9
>>
>> but the tests using this port (port2: 50235) were
>>     1, 3, 4, 6, 7, 8, 9
>>
>> and tests 2,4,6 were passed.
>>
>> so I think that the problem might be that the port was not fully
>> released when a test was trying to use it, even the port was closed by
>> the previous test.
>
> I don't think this is the case.
>
> Firstly, test 1 fails. There are no previous tests possibly holding on 
> to the required port. So the port must have been taken by some foreign 
> process. The port number being from the ephemeral range doesn't help 
> either, quite contrary.
>
> Secondly, a port can not be partially bound - either a process binds 
> to a port or not. Also, when a process exits all the bound ports must 
> be released. Since we are waiting for the exit code of the launched 
> test application before proceeding all the ports used by that 
> application must be released before the main test routine can continue.
Why did exception "Port already in use error: " happen for Test1, then 
the port was free for 3/4/6, and then the exception appeared again for 
7, 8, 9?

A port is possibly unavailable after being closed, because it can be in 
the state TIME_WAIT.

Your fix created a server socket but no client would connect to it, then 
the port could be available immediately after close(), not need to enter 
TIME_WAIT state, if so hopeful the fix could work.

Shanliang
>
>>
>> Your solution is to create a Server socket on a free port, then release
>> it when a test needs it. I suspect whether we will fall into same issue
>> here: the port would not be fully released when using it?
>
> No. SocketServer.close() is called synchronously right before the port 
> is going to be used. This call unbinds the socket and returns. At the 
> moment of the return the port is free. I've run the tests locally and 
> via JPRT and they are all passing.
>
> Thanks,
>
> -JB-
>
>>
>> Shanliang
>>
>> Jaroslav Bachorik wrote:
>>> Please, review this test fix.
>>>
>>> Issue : https://bugs.openjdk.java.net/browse/JDK-8035395
>>> Webrev: http://cr.openjdk.java.net/~jbachorik/8035395/webrev.00
>>>
>>> Currently, the test is using two fixed ports to start JMX connector
>>> and RMI registry when necessary. It can not deal with situations when
>>> the ports are not available. The patch is adding the ability to obtain
>>> ports from the ephemeral range and use them instead of the hardcoded
>>> ones. It also tries to minimize the chance of another process stealing
>>> the ports by holding the corresponding SocketServers open till right
>>> before the port is actually needed.
>>>
>>> Thanks,
>>>
>>> -JB-
>>
>