I'm using Netty server to solve this: reading a big file line by line and processing it. Doing it on single machine is still slow, so I've decided to use server to serve chunks of data to clients. That already works, but what I also want is that server shut downs itself when processed whole file. The source code I'm using right now is:
public static void main(String[] args) {
new Thread(() -> {
//reading the big file and populating 'dq' - data queue
}).start();
final EventLoopGroup bGrp = new NioEventLoopGroup(1);
final EventLoopGroup wGrp = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 100)
.childHandler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) {
ChannelPipeline p = ch.pipeline();
p.addLast(new StringDecoder());
p.addLast(new StringEncoder());
p.addLast(new ServerHandler(dq, bGrp, wGrp));
}
});
ChannelFuture f = b.bind(PORT).sync();
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
class ServerHandler extends ChannelInboundHandlerAdapter {
public ServerHandler(dq, bGrp, wGrp) {
//assigning params to instance fields
}
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
//creating bulk of data from 'dq' and sending to client
/* e.g.
ctx.write(dq.get());
*/
}
#Override
public void channelReadComplete(ChannelHandlerContext ctx) {
if (dq.isEmpty() /*or other check that file was processed*/ ) {
try {
ctx.channel().closeFuture().sync();
} catch (InterruptedException ie) {
//...
}
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
ctx.close();
ctx.executor().parent().shutdownGracefully();
}
}
Is the server shutdown in channelReadComplete(...) method correct? What I'm afraid is that there can still be another served client (e.g. sending big bulk in other client and with current client reached the end of 'dq').
The base code is from netty EchoServer/DiscardServer examples.
The question is : how to shut down netty server (from handler) when reached specific condition.
Thanks
You can not shutdown a server from a handler. What you could do is signal to a different thread that it should shutdown the server.
Related
on some day i decided to create a Netty Chat server using Tcp protocol. Currently, it successfully logging connect and disconnect, but channelRead0 in my handler is never fires. I tried Python client.
Netty version: 4.1.6.Final
Handler code:
public class ServerWrapperHandler extends SimpleChannelInboundHandler<String> {
private final TcpServer server;
public ServerWrapperHandler(TcpServer server){
this.server = server;
}
#Override
public void handlerAdded(ChannelHandlerContext ctx) {
System.out.println("Client connected.");
server.addClient(ctx);
}
#Override
public void handlerRemoved(ChannelHandlerContext ctx) {
System.out.println("Client disconnected.");
server.removeClient(ctx);
}
#Override
public void channelRead0(ChannelHandlerContext ctx, String msg) {
System.out.println("Message received.");
server.handleMessage(ctx, msg);
}
#Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
System.out.println("Read complete.");
super.channelReadComplete(ctx);
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
Output:
[TCPServ] Starting on 0.0.0.0:1052
Client connected.
Read complete.
Read complete.
Client disconnected.
Client code:
import socket
conn = socket.socket()
conn.connect(("127.0.0.1", 1052))
conn.send("Hello")
tmp = conn.recv(1024)
while tmp:
data += tmp
tmp = conn.recv(1024)
print(data.decode("utf-8"))
conn.close()
Btw, the problem was in my initializer: i added DelimiterBasedFrameDecoder to my pipeline, and this decoder is stopping the thread. I dont know why, but i dont needed this decoder, so i just deleted it, and everything started to work.
#Override
protected void initChannel(SocketChannel ch) throws Exception {
// Create a default pipeline implementation.
ChannelPipeline pipeline = ch.pipeline();
// Protocol Decoder - translates binary data (e.g. ByteBuf) into a Java object.
// Protocol Encoder - translates a Java object into binary data.
// Add the text line codec combination first,
pipeline.addLast("framer", new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter())); //<--- DELETE THIS
pipeline.addLast("decoder", new StringDecoder());
pipeline.addLast("encoder", new StringEncoder());
pipeline.addLast("handler", new ServerWrapperHandler(tcpServer));
}
i have an example that uses java 1.8 and netty 4.1.30.Final version IdleStateHandler to output the current time when no action is taken for 400 milliseconds. However, the current time is output at intervals of 2 seconds instead of 400 milliseconds.
here is my example code
Client.java
public void connect() {
EventLoopGroup workerGroup = new OioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(workerGroup)
.channel(RxtxChannel.class)
.option(RxtxChannelOption.BAUD_RATE, 38400)
.option(RxtxChannelOption.DATA_BITS, RxtxChannelConfig.Databits.DATABITS_8)
.option(RxtxChannelOption.PARITY_BIT, RxtxChannelConfig.Paritybit.NONE)
.option(RxtxChannelOption.STOP_BITS, RxtxChannelConfig.Stopbits.STOPBITS_1)
.handler(new ExampleChannelInitializer());
this.channel = bootstrap.connect(new RxtxDeviceAddress("COM1")).sync().channel();
this.channel.closeFuture().addListener(f -> {
workerGroup.shutdownGracefully();
});
} catch (Exception e) {
throw new ConnectionException(e.getMessage(), e);
}
}
ExampleChannelInitializer.java
#Override
protected void initChannel(RxtxChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(new IdleStateHandler(0, 0, 400, TimeUnit.MILLISECONDS));
pipeline.addLast(new ChannelInboundHandlerAdapter() {
#Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
System.out.println(LocalDateTime.now());
}
});
}
Console
2018-10-30T10:42:02.762
2018-10-30T10:42:04.789
2018-10-30T10:42:06.818
2018-10-30T10:42:08.844
2018-10-30T10:42:10.871
This is unfortunately just a matter of fact how the OIO transport and so RXTX work under the hood. You can make these more "precise" by using RxtxChannelOption.READ_TIMEOUT and RxtxChannelOption.WAIT_TIME and set these to some smaller value.
I am going through netty's documentation here and the diagram here.
My question is, the Timeserver is writing time into the socket, for the client to read the time. Shouldn't it use the ChannelOutboundHandlerAdapter ? Why is the logic in ChannelInboundHandlerAdapter ?
Couldn't understand, please explain.
Timeserver,
public class TimeServerHandler extends ChannelInboundHandlerAdapter {
#Override
public void channelActive(final ChannelHandlerContext ctx) { // (1)
final ByteBuf time = ctx.alloc().buffer(4); // (2)
time.writeInt((int) (System.currentTimeMillis() / 1000L + 2208988800L));
final ChannelFuture f = ctx.writeAndFlush(time); // (3)
f.addListener(new ChannelFutureListener() {
#Override
public void operationComplete(ChannelFuture future) {
assert f == future;
ctx.close();
}
}); // (4)
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
TimeClient,
public class TimeClient {
public static void main(String[] args) throws Exception {
String host = args[0];
int port = Integer.parseInt(args[1]);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap(); // (1)
b.group(workerGroup); // (2)
b.channel(NioSocketChannel.class); // (3)
b.option(ChannelOption.SO_KEEPALIVE, true); // (4)
b.handler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new TimeClientHandler());
}
});
// Start the client.
ChannelFuture f = b.connect(host, port).sync(); // (5)
// Wait until the connection is closed.
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
}
}
}
The reason we use a ChannelInboundHandlerAdapter is because, we are writing into the channel which was established by the client to the server. Since its inbound with respect to the server, we use a ChannelInboundHandlerAdapter. The Client connects to the Server, through the channel into which the server sends out the time.
Because your server will respond to incoming messages, it will need to implement interface ChannelInboundHandler, which defines methods for acting on inbound events.
Further, ChannelInboundHandlerAdapter has a straightforward API, and each of its methods can be overridden to hook into the event lifecycle at the appropriate point.
I just started learning Netty, hope this helps. :)
I have assigned to do TCP server in my organization to receive text message and split them. But unfortunately some of my
message characters become garbage (I have used JMeter as my TCP client). I have 2 questions related to this problem. Any help is highly appreciated.
Why we can not split my message using "»" (u00BB) character? It never worked and how we could use "»" as delimiter in DelimiterBasedFrameDecoder?
Why we receive garbage characters although I used UTF-8 in encoding/decoding? (Only manage to receive messages when I comment "pipeline.addLast("frameDecoder", new io.netty.handler.codec.DelimiterBasedFrameDecoder( 500000, byteDeli)" )
Sample request:
pov1‹1‹202030‹81056581‹0‹6‹565810000011‹0‹130418135639‹3‹4‹0‹cha7373737›chaE15E2512380›1›1«ban7373737›banE15E2512380›2›2«ind7373737›indE15E2512380›3›3»
Eclipse cosole: Recieved Request ::::::
pov1�1�202030�81056581�0�6�565810000011�0�130418135639�3�4�0�cha7373737�chaE15E2512380�1�1�ban7373737�banE15E2512380�2�2�ind7373737�indE15E2512380�3�3�
Server class:-
public void run() {
try {
System.out.println("2:run");
bootstrap
.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch)
throws Exception {
ChannelPipeline pipeline = ch.pipeline();
DTMTCPServiceHandler serviceHandler = context
.getBean(DTMTCPServiceHandler.class);
pipeline.addFirst(new LoggingHandler(
LogLevel.INFO));
byte[] delimiter = "\u00BB".getBytes(CharsetUtil.UTF_8);//»
ByteBuf byteDeli = Unpooled.copiedBuffer(delimiter);
pipeline.addLast(
"frameDecoder",
new io.netty.handler.codec.DelimiterBasedFrameDecoder(
500000, byteDeli)); // Decoders
pipeline.addLast("stringDecoder",
new StringDecoder(CharsetUtil.UTF_8));
pipeline.addLast("stringEncoder",
new StringEncoder(CharsetUtil.UTF_8));
pipeline.addLast("messageHandler",
serviceHandler);
}
}).option(ChannelOption.SO_BACKLOG, 128)
.childOption(ChannelOption.SO_KEEPALIVE, true);
serverChannel = bootstrap.bind(7070).sync().channel()
.closeFuture().sync().channel();
} catch (InterruptedException e) {
//error
logger.error("POSGatewayServiceThread : InterruptedException",
e);
System.out.println(e);
} finally {
//finally
System.out.println("finally");
serverChannel.close();
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
Handler class
public class DTMTCPServiceHandler extends ChannelInboundHandlerAdapter {
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
String posMessage = msg.toString();
System.out.println("Recieved Request :::::: " + posMessage);
String response = "-";
ByteBuf copy = null;
try {
//Called to separate splitter class
response = dtmtcpServiceManager.manageDTMTCPMessage(posMessage);
copy = Unpooled.copiedBuffer(response.getBytes());
} finally {
logger.info("Recieved Response :::::: " + response);
ctx.write(copy);
ctx.flush();
}
}
#Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
//Open
super.channelActive(ctx);
}
#Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
//End
super.channelReadComplete(ctx);
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
//exception
ctx.close();
}
}
Found the problem and it is not related to netty. Error is with the JMeter encoding. managed to solve this after modifying the "jmeter.properties" property file #\apache-jmeter-x.xx\bin.
tcp.charset=UTF-8
Sorry to trouble you guys, since false is with me.
I have application which uses both TCP and UDP protocols. Main assumption is that the client connects to server via TCP protocol and when connection is established, UDP datagrams are being send.
I have to support two scenarios of connecting to server:
- client connects when server is running
- client connects when server is down and retries connection until server starts again
For the first scenario everything works pretty fine: I got working both connections.
The problem is with second scenario. When client tries few times to connect via TCP and finally connects, the UDP connection function throws an exception:
java.net.SocketException: No buffer space available (maximum connections reached?): bind
at sun.nio.ch.Net.bind0(Native Method)
at sun.nio.ch.Net.bind(Net.java:344)
at sun.nio.ch.DatagramChannelImpl.bind(DatagramChannelImpl.java:684)
at sun.nio.ch.DatagramSocketAdaptor.bind(DatagramSocketAdaptor.java:91)
at io.netty.channel.socket.nio.NioDatagramChannel.doBind(NioDatagramChannel.java:192)
at io.netty.channel.AbstractChannel$AbstractUnsafe.bind(AbstractChannel.java:484)
at io.netty.channel.DefaultChannelPipeline$HeadContext.bind(DefaultChannelPipeline.java:1080)
at io.netty.channel.AbstractChannelHandlerContext.invokeBind(AbstractChannelHandlerContext.java:430)
at io.netty.channel.AbstractChannelHandlerContext.bind(AbstractChannelHandlerContext.java:415)
at io.netty.channel.DefaultChannelPipeline.bind(DefaultChannelPipeline.java:903)
at io.netty.channel.AbstractChannel.bind(AbstractChannel.java:197)
at io.netty.bootstrap.AbstractBootstrap$2.run(AbstractBootstrap.java:350)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:380)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:357)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116)
at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:137)
at java.lang.Thread.run(Thread.java:722)
When I restart client application without doing anything with server, client will connect with any problems.
What can cause a problem?
In below I attach source code of classes. All source code comes from examples placed in official Netty project page. The only thing which I have midified is that I replaced static variables and functions with non-static ones. It was caused that in future I will need many TCP-UDP connections to multiple servers.
public final class UptimeClient {
static final String HOST = System.getProperty("host", "192.168.2.193");
static final int PORT = Integer.parseInt(System.getProperty("port", "2011"));
static final int RECONNECT_DELAY = Integer.parseInt(System.getProperty("reconnectDelay", "5"));
static final int READ_TIMEOUT = Integer.parseInt(System.getProperty("readTimeout", "10"));
private static UptimeClientHandler handler;
public void runClient() throws Exception {
configureBootstrap(new Bootstrap()).connect();
}
private Bootstrap configureBootstrap(Bootstrap b) {
return configureBootstrap(b, new NioEventLoopGroup());
}
#Override
protected Object clone() throws CloneNotSupportedException {
return super.clone(); //To change body of generated methods, choose Tools | Templates.
}
Bootstrap configureBootstrap(Bootstrap b, EventLoopGroup g) {
if(handler == null){
handler = new UptimeClientHandler(this);
}
b.group(g)
.channel(NioSocketChannel.class)
.remoteAddress(HOST, PORT)
.handler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new IdleStateHandler(READ_TIMEOUT, 0, 0), handler);
}
});
return b;
}
void connect(Bootstrap b) {
b.connect().addListener(new ChannelFutureListener() {
#Override
public void operationComplete(ChannelFuture future) throws Exception {
if (future.cause() != null) {
handler.startTime = -1;
handler.println("Failed to connect: " + future.cause());
}
}
});
}
}
#Sharable
public class UptimeClientHandler extends SimpleChannelInboundHandler<Object> {
UptimeClient client;
public UptimeClientHandler(UptimeClient client){
this.client = client;
}
long startTime = -1;
#Override
public void channelActive(ChannelHandlerContext ctx) {
try {
if (startTime < 0) {
startTime = System.currentTimeMillis();
}
println("Connected to: " + ctx.channel().remoteAddress());
new QuoteOfTheMomentClient(null).run();
} catch (Exception ex) {
Logger.getLogger(UptimeClientHandler.class.getName()).log(Level.SEVERE, null, ex);
}
}
#Override
public void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
}
#Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) {
if (!(evt instanceof IdleStateEvent)) {
return;
}
IdleStateEvent e = (IdleStateEvent) evt;
if (e.state() == IdleState.READER_IDLE) {
// The connection was OK but there was no traffic for last period.
println("Disconnecting due to no inbound traffic");
ctx.close();
}
}
#Override
public void channelInactive(final ChannelHandlerContext ctx) {
println("Disconnected from: " + ctx.channel().remoteAddress());
}
#Override
public void channelUnregistered(final ChannelHandlerContext ctx) throws Exception {
println("Sleeping for: " + UptimeClient.RECONNECT_DELAY + 's');
final EventLoop loop = ctx.channel().eventLoop();
loop.schedule(new Runnable() {
#Override
public void run() {
println("Reconnecting to: " + UptimeClient.HOST + ':' + UptimeClient.PORT);
client.connect(client.configureBootstrap(new Bootstrap(), loop));
}
}, UptimeClient.RECONNECT_DELAY, TimeUnit.SECONDS);
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
void println(String msg) {
if (startTime < 0) {
System.err.format("[SERVER IS DOWN] %s%n", msg);
} else {
System.err.format("[UPTIME: %5ds] %s%n", (System.currentTimeMillis() - startTime) / 1000, msg);
}
}
}
public final class QuoteOfTheMomentClient {
private ServerData config;
public QuoteOfTheMomentClient(ServerData config){
this.config = config;
}
public void run() throws Exception {
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(group)
.channel(NioDatagramChannel.class)
.option(ChannelOption.SO_BROADCAST, true)
.handler(new QuoteOfTheMomentClientHandler());
Channel ch = b.bind(0).sync().channel();
ch.writeAndFlush(new DatagramPacket(
Unpooled.copiedBuffer("QOTM?", CharsetUtil.UTF_8),
new InetSocketAddress("192.168.2.193", 8193))).sync();
if (!ch.closeFuture().await(5000)) {
System.err.println("QOTM request timed out.");
}
}
catch(Exception ex)
{
ex.printStackTrace();
}
finally {
group.shutdownGracefully();
}
}
}
public class QuoteOfTheMomentClientHandler extends SimpleChannelInboundHandler<DatagramPacket> {
#Override
public void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg) throws Exception {
String response = msg.content().toString(CharsetUtil.UTF_8);
if (response.startsWith("QOTM: ")) {
System.out.println("Quote of the Moment: " + response.substring(6));
ctx.close();
}
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
If your server is Windows Server 2008 (R2 or R2 SP1), this problem is likely described and solved by this stackoverflow answer which refers to Microsoft KB article #2577795
This issue occurs because of a race condition in the Ancillary Function Driver
for WinSock (Afd.sys) that causes sockets to be leaked. With time, the issue
that is described in the "Symptoms" section occurs if all available socket
resources are exhausted.
If your server is Windows Server 2003, this problem is likely described and solved by this stackoverflow answer which refers to Microsoft KB article #196271
The default maximum number of ephemeral TCP ports is 5000 in the products that
are included in the "Applies to" section. A new parameter has been added in
these products. To increase the maximum number of ephemeral ports, follow these
steps...
...which basically means that you have run out of ephemeral ports.