Netty ServerSocket and Children Graceful Shutdown

Question

I would like to close the server socket on a Netty server and then wait for all children to finish processing before executing resource cleanup.

Step 1 Wait for the Netty server socket to close on the main thread using this code where b is an instance of ServerBootstrap

b.bind ( getPort ( p ) ).sync ().channel ().closeFuture ().sync ()

Step 2 Instruct the server socket to close from a different thread, somewhere else in the application

Step 3 Instruct all clients to shutdown, I will have application code that will do this

Step 4 Wait for all client sockets to close, this is what I want to know how to do. How can I get a list of all client sockets, children of the server, and then wait for all of them to close?

Netty version 4.1.1.Final

I setup the Netty server socket using the following code snippet

EventLoopGroup bossGroup = new NioEventLoopGroup ( 1 );
EventLoopGroup workerGroup = new NioEventLoopGroup ( Math.max ( 1, Runtime.getRuntime ().availableProcessors () / 2 ) );
try
{
  ServerBootstrap b = new ServerBootstrap ();
  b.group ( bossGroup, workerGroup )
  .channel ( NioServerSocketChannel.class )
  .childHandler ( new ServerInitializer ( sslctx, jsonIOManager, dispatcherPool, factory ) )
  .childOption ( ChannelOption.TCP_NODELAY, Boolean.TRUE )
  .childOption ( ChannelOption.SO_KEEPALIVE, Boolean.TRUE );

  // wait till server socket is closed    
  b.bind ( getPort ( p ) ).sync ().channel ().closeFuture ().sync ();
  // instruct all clients to shutdown
  dispatcherPool.shutdown ();

  // wait on all sockets that are children of the server socket to close
  // How can i do this?

}
finally
{
  bossGroup.shutdownGracefully ();
  workerGroup.shutdownGracefully ();
}

Answer 1

From the netty 4.x user guide it appears that simply waiting until the shutdownGracefully returns will wait until all sockets are closed.

Shutting down a Netty application is usually as simple as shutting down all EventLoopGroups you created via shutdownGracefully(). It returns a Future that notifies you when the EventLoopGroup has been terminated completely and all Channels that belong to the group have been closed.