Adding handlers to a closed Channel's pipeline

It appears the a ChannelPipeline will happily add a handler to a closed Channel’s pipeline and will call handlerAdded(...) but will not call handlerRemoved(...) or blow up in some other way to let the caller know that things aren’t in a good state.

Just wondering if there wouldn’t be edge cases where we’d potentially leak resources (e.g. SslHandler#handlerRemoved0(...) which is supposed to release a reference counted SSLEngine).

Expected behavior

Fail with Exception or handlerRemoved(...) getting called after handlerAdded(...)

Actual behavior

handlerAdded(...) getting called as if everything is ok

Steps to reproduce

Minimal yet complete reproducer code (or URL to code)

@Test
public void testHandlerAfterClose() throws Exception {
  EmbeddedChannel channel = new EmbeddedChannel();
  channel.close().syncUninterruptibly();
  
  assertFalse(channel.isActive());
  
  final CountDownLatch addedLatch = new CountDownLatch(1);
  final CountDownLatch removedLatch = new CountDownLatch(1);
  
  ChannelPipeline pipeline = channel.pipeline();
  pipeline.addLast(new ChannelHandlerAdapter() {
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
      addedLatch.countDown();
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
      removedLatch.countDown();
    }
  });
  
  assertTrue(addedLatch.await(1L, TimeUnit.SECONDS));
  assertTrue(removedLatch.await(1L, TimeUnit.SECONDS));
}

Netty version

JVM version (e.g. java -version)

OS version (e.g. uname -a)

[normanmaurer]

@Scottmitch I think non static exception is better as I not expect this to be thrown often and it will be better to have some context

[normanmaurer]

Yes I missed to close this 😕