Netty 4.0 channel gets null - nullpointerexception

Question

The setup
Windows 7 Professionnal
Eclipse Juno
Java jre7
Netty 4.0.0 Beta2
I have a netty server running on another machine. Then I have a program running on my machine, which is made to simulate many clients communicating with the server concurrently. In order to do that, I have a thread pool implemented with java.util.concurrent.ExecutorService . Each client creates a thread and submit it to the ExecutorService. Just before it ends, that thread creates another one with the same code. The submited code does those steps :
connect to server by sending a handshake (netty bootstrap A and channel A)
get the token from the handshake response
connect to server (netty bootstrap B and channel B)
send one request to server
receive the response
close the connection
create another thread with the same code
The problem
I sometimes get a NullPointerException in NettySocketCommunication.sendMessage(), on channel.write(byteBuf) when sending a request to the server.
01728 16:25:23.870 [nioEventLoopGroup-3804-2] ERROR
c.f.s.virtualuser.VirtualUser - java.lang.RuntimeException:
java.lang.NullPointerException at
c.f.s.virtualuser.VirtualUser.processMessageStep(VirtualUser.java:324)
at
c.f.s.virtualuser.VirtualUser.processNextStep(VirtualUser.java:252)
at
c.f.s.virtualuser.VirtualUser.onChannelConnected(VirtualUser.java:395)
at
c.f.s.c.m.handler.ClientSocketBasedHandler.channelActive(ClientSocketBasedHandler.java:95)
at
io.netty.channel.DefaultChannelHandlerContext.invokeChannelActive(DefaultChannelHandlerContext.java:774)
at
io.netty.channel.DefaultChannelHandlerContext.fireChannelActive(DefaultChannelHandlerContext.java:760)
at
io.netty.channel.ChannelStateHandlerAdapter.channelActive(ChannelStateHandlerAdapter.java:58)
at
io.netty.channel.DefaultChannelHandlerContext.invokeChannelActive(DefaultChannelHandlerContext.java:774)
at
io.netty.channel.DefaultChannelHandlerContext.fireChannelActive(DefaultChannelHandlerContext.java:760)
at
io.netty.channel.DefaultChannelPipeline.fireChannelActive(DefaultChannelPipeline.java:884)
at
io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:223)
at
io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:417)
at
io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:365)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:302) at
io.netty.channel.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:110)
at java.lang.Thread.run(Unknown Source)
Caused by:
java.lang.NullPointerException: null at
c.f.s.c.m.NettySocketCommunication.sendMessage(NettySocketCommunication.java:109)
at
c.f.s.virtualuser.VirtualUser.processMessageStep(VirtualUser.java:317)
... 15 common frames omitted
The code
I removed some logging and comments to make the code blocks shorter. I also have the VirtualUser.java class (not shown here) that implements both IVirtualUserCommunication and IVirtualUserMessages interfaces.
[AbstractVirtualUserCommunication.java]
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundMessageHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.DefaultLastHttpContent;
import io.netty.handler.codec.http.HttpRequestEncoder;
import io.netty.handler.codec.http.HttpResponseDecoder;
import io.netty.util.CharsetUtil;
import [...].Amf3;
import [...].Properties;
import [...].LogFactory;
import [...].Logger;
import [...].AbstractRequest;
import [...].IRouterMessage;
import [...].RouterMessage;
import [...].FrimaHandshake;
import [...].IVirtualUserCommunication;
public abstract class AbstractVirtualUserCommunication implements IVirtualUserCommunication
{
protected static Logger Log = LogFactory.getInstance().getLogger(AbstractVirtualUserCommunication.class);
protected String CONFIG_APPLICATION = "target.server.application";
protected String application;
protected String CONFIG_VERSION = "target.server.version";
protected String version;
protected String CONFIG_HANDSHAKE_PORT = "netty.handshake.port";
protected final int defaultHandshakePort = 80;
// The following variables are used by both HTTP and SOCKET communication
protected Bootstrap bootstrapHandshake; // Netty bootstrap used only for handshake
protected Channel channelHandshake; // Netty channel used only for handshake
protected String token; // The token received through handshake process
// Host & port are set in the connect() method
protected String host;
protected int port;
protected Bootstrap bootstrap; // Netty bootstrap used for communication
protected Channel channel; // Netty channel used for communication
/** Connect to the server to get the token */
public void sendHandshake(String host)
{
// Get properties, with default values if they are not specified
this.application = Properties.getString(CONFIG_APPLICATION, "snowstorm");
this.version = Properties.getString(CONFIG_VERSION, "0.0.1");
int handshakePort = Properties.getInt(CONFIG_HANDSHAKE_PORT, defaultHandshakePort);
bootstrapHandshake = new Bootstrap();
try
{
bootstrapHandshake.group(new NioEventLoopGroup());
bootstrapHandshake.channel(NioSocketChannel.class);
bootstrapHandshake.handler(new HandShakeInitializer(/* this */));
// Connect and listen on handshake host/port
channelHandshake = bootstrapHandshake.connect(host, handshakePort).sync().channel();
channelHandshake.closeFuture().sync();
}
catch (InterruptedException e)
{
Log.error(e);
}
finally
{
bootstrapHandshake.shutdown();
}
}
/** Method called after completion of the handshake (the token has been set). */
protected abstract void afterHandshake();
/** Connect to the target server for stress test script execution. */
protected void connect(ChannelHandler handler)
{
bootstrap = new Bootstrap();
try
{
// Initialize the pipeline
bootstrap.group(new NioEventLoopGroup());
bootstrap.channel(NioSocketChannel.class);
bootstrap.handler(handler);
// Connect and listen on host/port
channel = bootstrap.connect(host, port).sync().channel();
if (channel == null)
{
Log.error("PROBLEM : The channel is null in the afterHandshake() method");
}
channel.closeFuture().sync();
}
catch (InterruptedException e)
{
Log.error(e);
}
finally
{
bootstrap.shutdown();
}
}
/** Create a RouterMessage with the specified request. */
protected IRouterMessage buildMessage(AbstractRequest request)
{
RouterMessage routerMessage = new RouterMessage();
routerMessage.bytes = Amf3.serialize(request);
routerMessage.token = this.token;
routerMessage.application = this.application;
routerMessage.version = this.version;
return routerMessage;
}
#Override
public void disconnect()
{
// TODO Is it dangerous to not call channel.close() ??
if (channel != null)
{
channel.close().awaitUninterruptibly();
}
else
{
Log.error("PROBLEM : The channel is null when calling the disconnect() method");
}
bootstrap.shutdown();
}
#Override
public boolean isConnected()
{
if (channel == null)
{
return false;
}
return channel.isActive();
}
private class HandShakeInitializer extends ChannelInitializer<SocketChannel>
{
public HandShakeInitializer()
{
super();
}
#Override
protected void initChannel(SocketChannel socketChannel) throws Exception
{
socketChannel.pipeline().addLast("encoder", new HttpRequestEncoder());
socketChannel.pipeline().addLast("decoder", new HttpResponseDecoder());
socketChannel.pipeline().addLast("handler", new HandShakeHandler(/* communication */));
}
}
private class HandShakeHandler extends ChannelInboundMessageHandlerAdapter<Object>
{
public HandShakeHandler()
{
super();
}
#Override
public void channelActive(ChannelHandlerContext ctx) throws Exception
{
super.channelActive(ctx);
ctx.write(FrimaHandshake.create(null, version, application));
ctx.flush();
}
#Override
public void messageReceived(ChannelHandlerContext ctx, Object msg) throws Exception
{
if (msg instanceof DefaultLastHttpContent)
{
DefaultLastHttpContent defaultLastHttpContent = (DefaultLastHttpContent) msg;
String content = defaultLastHttpContent.data().toString(CharsetUtil.UTF_8);
// Format = token~publicDNS and we only need the token here
token = content;// .split("~")[0];
Log.debug("Starting a bot with token " + token);
afterHandshake();
}
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception
{
Log.error(cause);
ctx.close();
}
}
}
[NettySocketCommunication.java]
import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelFuture;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import [..­.].AbstractRequest;
import [..­.].IRouterMessage;
import [..­.].Serializer;
import [..­.].ClientSocketBasedHandler;
import [..­.].ClientSocketBasedInitializer;
import [..­.].IVirtualUserMessages;
public class NettySocketCommunication extends AbstractVirtualUserCommunication
{
private ClientSocketBasedHandler handler;
private ChannelFuture testChannelFuture;
public NettySocketCommunication()
{
super();
Log.setLevelToInfo();
this.handler = new ClientSocketBasedHandler();
}
#Override
public void setVirtualUser(IVirtualUserMessages virtualUser)
{
this.handler.setVirtualUser(virtualUser);
}
#Override
public void connect(String host, int port)
{
this.host = host;
this.port = port;
// Get the token from the server through the handshake process
sendHandshake(host);
}
#Override
public boolean connectTest(String host, int port)
{
boolean connectSuccess = false;
bootstrap = new Bootstrap();
// Initialize the pipeline
bootstrap.group(new NioEventLoopGroup());
bootstrap.channel(NioSocketChannel.class);
bootstrap.handler(new ClientSocketBasedInitializer(new ClientSocketBasedHandler()));
// Listen on host/port (connect a channel)
testChannelFuture = bootstrap.connect(host, port);
testChannelFuture.awaitUninterruptibly();
if (testChannelFuture.isSuccess())
{
connectSuccess = true;
}
testChannelFuture.channel().close().awaitUninterruptibly();
bootstrap.shutdown();
return connectSuccess;
}
#Override
protected void afterHandshake()
{
super.connect(new ClientSocketBasedInitializer(handler));
}
#Override
public void sendMessage(AbstractRequest request)
{
IRouterMessage routerMessage = buildMessage(request);
ByteBuf byteBuf = Serializer.encode(routerMessage, true);
// Send message
channel.write(byteBuf);
channel.flush();
}
}
[ClientSocketBasedHandler.java]
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundMessageHandlerAdapter;
import java.util.ArrayList;
import java.util.List;
import [...].Amf3;
import [...].LogFactory;
import [...].Logger;
import [...].IMessage;
import [...].IRouterMessage;
import [...].IVirtualUserMessages;
public class ClientSocketBasedHandler extends ChannelInboundMessageHandlerAdapter<IRouterMessage>
{
protected static Logger Log = LogFactory.getInstance().getLogger(ClientSocketBasedHandler.class);
private IVirtualUserMessages virtualUser;
public ClientSocketBasedHandler()
{
super();
Log.setLevelToInfo();
}
public void setVirtualUser(IVirtualUserMessages virtualUser)
{
this.virtualUser = virtualUser;
}
#Override
public void messageReceived(ChannelHandlerContext ctx, IRouterMessage routerMessage) throws Exception
{
List<IMessage> messages = deserializeMessages(routerMessage.getBytes());
for (IMessage message : messages)
{
Log.debug("Received socket : " + message);
if (virtualUser == null)
{
throw new RuntimeException("Must call the setVirtualUser() method before receiving messages");
}
virtualUser.onManticoreMessageReceived(message);
}
}
protected List<IMessage> deserializeMessages(byte[] bytes)
{
Object probablyMessages = Amf3.deserialize(bytes);
List<IMessage> messages = null;
// List of Messages
if (probablyMessages instanceof ArrayList)
{
messages = (List<IMessage>) probablyMessages;
}
// Single Message
else if (probablyMessages instanceof IMessage)
{
messages = new ArrayList<IMessage>(1);
messages.add((IMessage) probablyMessages);
}
// Probably Pollution
else
{
Log.error("Cannot deserialize message '{}'", probablyMessages.toString());
}
return messages;
}
#Override
public void channelActive(ChannelHandlerContext ctx)
{
if (virtualUser != null)
{
virtualUser.onChannelConnected();
}
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception
{
Log.error(cause);
ctx.close();
}
}
The search
I looked at netty channels related questions on stack overflow, but couldn't find anything relevant to my case.
Links
http://netty.io/4.0/api/io/netty/channel/Channel.html
http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ExecutorService.html