Trustin Lee wrote:
>
> If you take a look into the VmPipeFilterChain, there's a queue for such a
> case:
>
> ...
>
> So, I think it will work fine without causing a dead lock or
> messageReceived event to be fired before sessionOpened is fired. Does
> it make sense?
>
In a VmPipe, I've run into some problems with sessionCreated not completing
before sessionOpened and messageReceived are called. I thought that mina
guaranteed that sessionCreated would be completed before sessionOpened and
messageReceived. I think this stems from the following code in
ExecutorFilter:
public void sessionCreated(NextFilter nextFilter, IoSession session) {
nextFilter.sessionCreated(session);
}
All other event handlers run the nextFilter a separate thread thusly:
public void sessionOpened(NextFilter nextFilter, IoSession session) {
fireEvent(nextFilter, session, EventType.OPENED, null);
}
The issue appears if the VmPipeConnector writes a message while the
VmPipeAcceptor's IoHandler is still envoking sessionCreated.
The program below illustrates the problem. It outputs a String with events
appended in the order they finish. We would expect it to print
"sessionCreated, sessionOpened, messageReceived, ", but it prints
"sessionOpened, messageReceived, sessionCreated, ".
public class VmPipeSessionCreatedTimingBug {
public static void main(String[] args) throws Exception {
final Semaphore semaphore = new Semaphore(0);
final StringBuffer stringBuffer = new StringBuffer();
VmPipeAcceptor vmPipeAcceptor = new VmPipeAcceptor();
final VmPipeAddress vmPipeAddress = new VmPipeAddress(12345);
vmPipeAcceptor.bind(vmPipeAddress, new IoHandlerAdapter() {
@Override
public void sessionCreated(IoSession session) throws
Exception {
// pretend we are doing some time-consuming
work. For
// performance reasons, you would never want to
do time
// consuming work in sessionCreated.
// However, this increases the likelihood of
the timing bug.
Thread.sleep(5000);
stringBuffer.append("sessionCreated, ");
}
@Override
public void sessionOpened(IoSession session) throws
Exception {
Thread.sleep(1000);
stringBuffer.append("sessionOpened, ");
}
@Override
public void messageReceived(IoSession session, Object
message)
throws Exception {
stringBuffer.append("messageReceived, ");
semaphore.release();
}
});
final VmPipeConnector vmPipeConnector = new VmPipeConnector();
ConnectFuture connectFuture =
vmPipeConnector.connect(vmPipeAddress,
new IoHandlerAdapter() {
@Override
public void sessionOpened(IoSession
session)
throws Exception {
session.write(ByteBuffer.wrap(new byte[1]));
}
});
semaphore.tryAcquire(5, TimeUnit.SECONDS);
connectFuture.getSession().close();
vmPipeAcceptor.unbindAll();
System.out.println(stringBuffer);
}
}
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