DIRMINA-1140 - detecting specific case of InterruptedException in NioDatagramAcceptor

[the-thing]

Fix for DIRMINA-1140

I was able to retrofit JIRA's attached minimal working example into a test case. The title is slightly wrong as this can happen for a single acceptor that is being disposed.

org.apache.mina.core.service.AbstractIoService#dispose(boolean) is the root cause. When a null java.util.concurrent.Executor is passed in org.apache.mina.core.service.AbstractIoService#AbstractIoService creates a new java.util.concurrent.Executors#newCachedThreadPool() and the service is responsible for shutting it down during disposal.

When java.util.concurrent.ExecutorService is shut down it usually interrupts threads which leads to

mina/mina-core/src/main/java/org/apache/mina/transport/socket/nio/NioDatagramAcceptor.java

Line 169 in b6739d2

lock.acquire();

interrupted exception being thrown here.

Suggested fix is to check the flag if service is being disposed when java.lang.InterruptedException exception is caught and do not rethrow it. I checked and this doesn't happen for org.apache.mina.transport.socket.nio.NioSocketAcceptor etc.

Aleternative fixes:

• use java.util.concurrent.Semaphore#acquireUninterruptibly() instead of java.util.concurrent.Semaphore#acquire(), but since the thread was interrupted we probably want it to be responsive and do not attempt to acquire the lock (haven't tested this solution).

• completely ignore - catch without logging / throwing InterruptedException. Not the best since if the custom Executor is passed to NioDatagramAcceptor and is shutdown before the unbind happened, it will lead to similar error, but in this case we actually want to throw it for the user to know about bad shutdown order (demo in org.apache.mina.transport.socket.nio.NioDatagramAcceptorTest#shouldThrowExceptionWhenThreadIsInterruptedAndServiceIsNotDisposing case)

[elecharny]

Looks good to me.

And thanks for the cleanup of the code I pushed in a hurry ;-)

[the-thing]

Thanks. No probs. When I see a bug or something to improve I see bread on the table ;).