Netty: What is the right way to share NioClientSocketChannelFactory among multiple Netty Clients - tcp

Question

I am new to Netty. I am using “Netty 3.6.2.Final”. I have created a Netty Client (MyClient) that talks to a remote server (The server implements a custom protocol based on TCP). I create a new ClientBootstrap instance for each MyClient instance (within the constructor).
My question is if I share “NioClientSocketChannelFactory” factory object among all the instances of MyClient then when/how do I release all the resources associated with the “NioClientSocketChannelFactory”?
In other words, since my Netty Client runs inside a JBOSS container running 24x7, should I release all resources by calling “bootstrap.releaseExternalResources();” and when/where should I do so?
More Info: My Netty Client is called from two scenarios inside a JBOSS container. First, in an infinite for loop with each time passing the string that needs to be sent to the remote server (in effect similar to below code)
for( ; ; ){
//Prepare the stringToSend
//Send a string and receive a string
String returnedString=new MyClient().handle(stringToSend);
}
Another scenarios is my Netty Client is called within concurrent threads with each thread calling “new MyClient().handle(stringToSend);”.
I have given the skeleton code below. It is very similar to the TelnetClient example at Netty website.
MyClient
import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;
public class MyClient {
//Instantiate this only once per application
private final static Timer timer = new HashedWheelTimer();
//All below must come from configuration
private final String host ="127.0.0.1";
private final int port =9699;
private final InetSocketAddress address = new InetSocketAddress(host, port);
private ClientBootstrap bootstrap;
//Timeout when the server sends nothing for n seconds.
static final int READ_TIMEOUT = 5;
public MyClient(){
bootstrap = new ClientBootstrap(NioClientSocketFactorySingleton.getInstance());
}
public String handle(String messageToSend){
bootstrap.setOption("connectTimeoutMillis", 20000);
bootstrap.setOption("tcpNoDelay", true);
bootstrap.setOption("keepAlive", true);
bootstrap.setOption("remoteAddress", address);
bootstrap.setPipelineFactory(new MyClientPipelineFactory(messageToSend,bootstrap,timer));
// Start the connection attempt.
ChannelFuture future = bootstrap.connect();
// Wait until the connection attempt succeeds or fails.
channel = future.awaitUninterruptibly().getChannel();
if (!future.isSuccess()) {
return null;
}
// Wait until the connection is closed or the connection attempt fails.
channel.getCloseFuture().awaitUninterruptibly();
MyClientHandler myClientHandler=(MyClientHandler)channel.getPipeline().getLast();
String messageReceived=myClientHandler.getMessageReceived();
return messageReceived;
}
}
Singleton NioClientSocketChannelFactory
public class NioClientSocketFactorySingleton {
private static NioClientSocketChannelFactory nioClientSocketChannelFactory;
private NioClientSocketFactorySingleton() {
}
public static synchronized NioClientSocketChannelFactory getInstance() {
if ( nioClientSocketChannelFactory == null) {
nioClientSocketChannelFactory=new NioClientSocketChannelFactory(
Executors.newCachedThreadPool(),
Executors.newCachedThreadPool());
}
return nioClientSocketChannelFactory;
}
protected void finalize() throws Throwable {
try{
if(nioClientSocketChannelFactory!=null){
// Shut down thread pools to exit.
nioClientSocketChannelFactory.releaseExternalResources();
}
}catch(Exception e){
//Can't do anything much
}
}
}
MyClientPipelineFactory
public class MyClientPipelineFactory implements ChannelPipelineFactory {
private String messageToSend;
private ClientBootstrap bootstrap;
private Timer timer;
public MyClientPipelineFactory(){
}
public MyClientPipelineFactory(String messageToSend){
this.messageToSend=messageToSend;
}
public MyClientPipelineFactory(String messageToSend,ClientBootstrap bootstrap, Timer timer){
this.messageToSend=messageToSend;
this.bootstrap=bootstrap;
this.timer=timer;
}
public ChannelPipeline getPipeline() throws Exception {
// Create a default pipeline implementation.
ChannelPipeline pipeline = pipeline();
// Add the text line codec combination first,
//pipeline.addLast("framer", new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));
pipeline.addLast("decoder", new StringDecoder());
pipeline.addLast("encoder", new StringEncoder());
//Add readtimeout
pipeline.addLast("timeout", new ReadTimeoutHandler(timer, MyClient.READ_TIMEOUT));
// and then business logic.
pipeline.addLast("handler", new MyClientHandler(messageToSend,bootstrap));
return pipeline;
}
}
MyClientHandler
public class MyClientHandler extends SimpleChannelUpstreamHandler {
private String messageToSend="";
private String messageReceived="";
public MyClientHandler(String messageToSend,ClientBootstrap bootstrap) {
this.messageToSend=messageToSend;
this.bootstrap=bootstrap;
}
#Override
public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e){
e.getChannel().write(messageToSend);
}
#Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e){
messageReceived=e.getMessage().toString();
//This take the control back to the MyClient
e.getChannel().close();
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
// Close the connection when an exception is raised.
e.getChannel().close();
}
}

Answer 1

You should only call releaseExternalResources() once you are sure you not need it anymore. This may be for example when the application gets stopped or undeployed.