Issue2517

Observed on Windows regrtest, I get a lot of these (below) after test_socket_jy. It's not actually a test failure, but seems to indicate we have something wrong.
 [exec] Aug 31, 2016 7:27:46 AM io.netty.util.concurrent.DefaultPromise safeExecute
 [exec] SEVERE: Failed to submit a listener notification task. Event loop shut down?
 [exec] java.util.concurrent.RejectedExecutionException: event executor terminated
 [exec] at io.netty.util.concurrent.SingleThreadEventExecutor.reject(SingleThreadEventExecutor.java:840)
 [exec] at io.netty.util.concurrent.SingleThreadEventExecutor.offerTask(SingleThreadEventExecutor.java:342)
 [exec] at io.netty.util.concurrent.SingleThreadEventExecutor.addTask(SingleThreadEventExecutor.java:335)
 [exec] at io.netty.util.concurrent.SingleThreadEventExecutor.execute(SingleThreadEventExecutor.java:765)
 [exec] at io.netty.util.concurrent.DefaultPromise.safeExecute(DefaultPromise.java:767)
 [exec] at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:435)
 [exec] at io.netty.util.concurrent.DefaultPromise.addListener(DefaultPromise.java:170)
 [exec] at io.netty.channel.DefaultChannelPromise.addListener(DefaultChannelPromise.java:93)
 [exec] at io.netty.channel.DefaultChannelPromise.addListener(DefaultChannelPromise.java:28)
 [exec] at sun.reflect.GeneratedMethodAccessor332.invoke(Unknown Source)
 [exec] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 [exec] at java.lang.reflect.Method.invoke(Method.java:606)
 [exec] at org.python.core.PyReflectedFunction.__call__(PyReflectedFunction.java:186)
 [exec] at org.python.core.PyReflectedFunction.__call__(PyReflectedFunction.java:204)
 [exec] at org.python.core.PyObject.__call__(PyObject.java:497)
 [exec] at org.python.core.PyObject.__call__(PyObject.java:501)
 [exec] at org.python.core.PyMethod.__call__(PyMethod.java:141)
 [exec] at _socket$py.close89ドル(C:\Users\Jeff\Documents\Eclipse\jython-trunk\dist\Lib\_socket.py:1092)
 [exec] at _socket$py.call_function(C:\Users\Jeff\Documents\Eclipse\jython-trunk\dist\Lib\_socket.py)
 [exec] at org.python.core.PyTableCode.call(PyTableCode.java:167)
 [exec] at org.python.core.PyBaseCode.call(PyBaseCode.java:139)
 [exec] at org.python.core.PyFunction.__call__(PyFunction.java:413)
 [exec] at org.python.core.PyMethod.__call__(PyMethod.java:126)
 [exec] at _socket$py.close127ドル(C:\Users\Jeff\Documents\Eclipse\jython-trunk\dist\Lib\_socket.py:1501)
 [exec] at _socket$py.call_function(C:\Users\Jeff\Documents\Eclipse\jython-trunk\dist\Lib\_socket.py)
 [exec] at org.python.core.PyTableCode.call(PyTableCode.java:167)
 [exec] at org.python.core.PyBaseCode.call(PyBaseCode.java:139)
 [exec] at org.python.core.PyFunction.__call__(PyFunction.java:413)
 [exec] at org.python.core.PyMethod.__call__(PyMethod.java:126)
 [exec] at _socket$py.__del__129ドル(C:\Users\Jeff\Documents\Eclipse\jython-trunk\dist\Lib\_socket.py:1514)
 [exec] at _socket$py.call_function(C:\Users\Jeff\Documents\Eclipse\jython-trunk\dist\Lib\_socket.py)
 [exec] at org.python.core.PyTableCode.call(PyTableCode.java:167)
 [exec] at org.python.core.PyBaseCode.call(PyBaseCode.java:139)
 [exec] at org.python.core.PyFunction.__call__(PyFunction.java:413)
 [exec] at org.python.core.PyMethod.__call__(PyMethod.java:126)
 [exec] at org.python.core.PyMethod.__call__(PyMethod.java:117)
 [exec] at org.python.core.PyObjectDerived.__del_derived__(PyObjectDerived.java:24)
 [exec] at org.python.core.finalization.FinalizeTrigger.runFinalizer(FinalizeTrigger.java:82)
 [exec] at org.python.core.finalization.FinalizeTrigger.performFinalization(FinalizeTrigger.java:168)
 [exec] at org.python.core.finalization.FinalizeTrigger.finalize(FinalizeTrigger.java:207)
 [exec] at java.lang.System2ドル.invokeFinalize(System.java:1210)
 [exec] at java.lang.ref.Finalizer.runFinalizer(Finalizer.java:98)
 [exec] at java.lang.ref.Finalizer.access100ドル(Finalizer.java:34)
 [exec] at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:210)

This is a side effect of our upgrade to Netty 4.1 - before Netty dropped these notifications.
We just need to setup the appropriate listener to quiet. To be researched what that is, but we should get this done for the RC - random stuff to stderr has impact on usage.

The relevant Netty change is https://github.com/netty/netty/issues/2166, which happened in 4.0.16; but most likely 4.1 made this more prominent. My recollection is that I don't believe it's possible to have Python socket closing semantics without attempting to close the pool as soon as possible - as it is, we wait up to 100ms. See the _realsocket._finish_closing method in Lib/socket.py for more on what is being done to close the socket.
Therefore we need to take advantage of the rejected logger, which is under the name io.netty.util.concurrent.DefaultPromise.rejectedExecution; see https://github.com/netty/netty/commit/2ba00cd358de2f4fbfef12b0be63605d49826f1a
Assuming SL4J + Logback is still being used, this advice on StackOverflow should be relevant: http://stackoverflow.com/a/11852808/423006. In particular we can put a suitably configured logback.xml in jython.jar or jython-dev.jar to remove this logging: http://logback.qos.ch/manual/configuration.html#auto_configuration 

I verified by looking at the source of Netty that logback is used. Now it's just a question of implementing the appropriate silencing.

I'll take a look at this. Following Jim's advice (silence the messages) as a pragmatic answer, but also on the lookout for a root cause. It seems to be that we are giving work to a worker we already retired, but quite why I can't see.

Not logback (which seems an excellent library BTW) but plain ol' java.util.logging. Netty adapts to what's available https://github.com/netty/netty/blob/4.1/common/src/main/java/io/netty/util/internal/logging/InternalLoggerFactory.java#L19 .
I'm going to quiet the stack dumps I observe in test_socket only, treating them for now as a side effect of the way we keep making and tearing things up when testing. There are two loggers: one producing at SEVERE, the other at WARNING, which I'll set to OFF and SEVERE respectively.
I suspect there are real causes here we could fix, along with the hang I regularly experience, but I'd need to know more about Netty and sockets -- which I'd like to.