GC closes my ServerSocket

[Weijun Wang]

 > Would this be a good candidate to use Automatic Resource Management ?

Correct. I'll remember to use it the next time.

Thanks
Max

On 06/13/2012 08:23 PM, Neil Richards wrote:
> On Wed, 2012-06-13 at 17:23 +0800, Weijun Wang wrote:
>> Please anyone take a review:
>>
>>      http://cr.openjdk.java.net/~weijun/7176574/webrev.00/
>>
>> By assigning to a local variable hopefully it stays alive on the stack
>> during the whole method.
>>
>> Noreg-self.
>>
>> *Chris*: I didn't indented the whole test by wrapping them into a
>> try-finally (or try-with-resources) block. The test runs in othervm and
>> I guess the sockets will be closed anyway.
>>
>> Thanks
>> Max
>>
>> On 06/13/2012 05:08 PM, Chris Hegarty wrote:
>>>
>>>
>>> On 13/06/2012 09:51, Alan Bateman wrote:
>>>> On 13/06/2012 09:38, Weijun Wang wrote:
>>>>> Hi All
>>>>>
>>>>> I have a test that basically looks like:
>>>>>
>>>>> int p = new ServerSocket(0).getLocalPort();
>>>>> //....
>>>>> new Socket("localhost", p);
>>>>>
>>>>> Recently it's failing on solaris-i586, and after some investigation, I
>>>>> realize that the ServerSocket object is GC'ed and auto-closed.
>>>>>
>>>>> (But why only recently?)
>>>>>
>>>>> So I change the first line to
>>>>>
>>>>> ServerSocket ss = new ServerSocket(0);
>>>>> int p = ss.getLocalPort();
>>>>>
>>>>> and it's running fine.
>>>>>
>>>>> I want to know if the ServerSocket object still has a chance to be
>>>>> closed. If yes, I'll add a
>>>>>
>>>>> ss.close();
>>>>>
>>>>> at the end to be safer.
>>>>>
>>>>> Thanks
>>>>> Max
>>>> HotSpot changes I assume, perhaps changes to the reference processing or
>>>> default heap settings.
>>>
>>> Right, I assume there was some VM change that started this test to fail
>>> recently, but clearly this is a test issue. It was just passing all this
>>> time by accident, and there is an inherent race between the test and the
>>> GC/finalizer thread.
>>>
>>> You should fix the test as you suggested. Also close the serversocket in
>>> a finally block ( or equivalent ). You should not rely on the finalizer
>>> to close it out.
>>>
>>> -Chris.
>>>
>>>>
>>>> -Alan
>
> Would this be a good candidate to use Automatic Resource Management ?
>
> i.e. instead of doing this:
>
>          ServerSocket ss1 = null;
>          ServerSocket ss2 = null;
>          try {
>                  ss1 = new ServerSocket(0);
>                  ss2 = new ServerSocket(0);
>                  int p1 = ss1.getLocalPort();
>                  int p2 = ss1.getLocalPort();
>                  //...
>          } finally {
>                  if (ss1 != null) ss1.close();
>                  if (ss2 != null) ss2.close();
>          }
>
> one would do this:
>
>          try (ServerSocket ss1 = new ServerSocket(0);
>                          ServerSocket ss2 = new ServerSocket(0)) {
>                  int p1 = ss1.getLocalPort();
>                  int p2 = ss1.getLocalPort();
>                  //...
>          }
>
> Regards,
> Neil
>