Netty timeout mechanism and implementation of heartbeat program

This article describes the principle of the Netty timeout mechanism and how to send a heartbeat to maintain the connection when the connection is idle.

Introduction to the Netty timeout mechanism

The Netty timeout type idlestate is mainly divided into:

All_idle: No data received or sent over time

Reader_idle: No data received over time

Writer_idle: No data sent over time

Under Netty's timeout package, the main classes are:

Idlestateevent: Timed-out event

Idlestatehandler: Timeout Status processing

Readtimeouthandler: Read Timeout status processing

Writetimeouthandler: Write timeout status processing

where Idlestatehandler contains read \ Write timeout status processing, such as

private static final int read_idel_time_out = 4; Read timeout

private static final int write_idel_time_out = 5;//Write timeout

private static final int all_idel_time_out = 7; All timeouts

New Idlestatehandler (Read_idel_time_out,

Write_idel_time_out, All_idel_time_out, timeunit.seconds));

In the example above, the read timeout defined in Idlestatehandler is 4 seconds, the write timeout is 5 seconds, and all other timeouts are 7 seconds.

Application Idlestatehandler

Since Idlestatehandler includes read \ Write timeout status processing, many times Readtimeouthandler, Writetimeouthandler can be used. Define another channelinitializer named Heartbeathandlerinitializer:

public class Heartbeathandlerinitializer extends Channelinitializer {

private static final int read_idel_time_out = 4; Read timeout

private static final int write_idel_time_out = 5;//Write timeout

private static final int all_idel_time_out = 7; All timeouts

@Override

protected void Initchannel (Channel ch) throws Exception {

Channelpipeline pipeline = Ch.pipeline ();

Pipeline.addlast (New Idlestatehandler (Read_idel_time_out,

Write_idel_time_out, All_idel_time_out, timeunit.seconds)); 1

Pipeline.addlast (New Heartbeatserverhandler ()); 2

}

}

Use Idlestatehandler to set the time for read and write timeouts

Defines a Heartbeatserverhandler processor that is used to handle timeouts when the heartbeat is sent

Defines a heartbeat processor

public class Heartbeatserverhandler extends Channelinboundhandleradapter {

Return a unreleasable view on the given bytebuf

Which'll just ignore release and retain calls.

private static final Bytebuf heartbeat_sequence = unpooled

. Unreleasablebuffer (Unpooled.copiedbuffer ("Heartbeat",

Charsetutil.utf_8)); 1

@Override

public void usereventtriggered (Channelhandlercontext ctx, Object evt)

Throws Exception {

if (evt instanceof idlestateevent) {//2

Idlestateevent event = (idlestateevent) evt;

String type = "";

if (event.state () = = Idlestate.reader_idle) {

Type = "Read Idle";

} else if (event.state () = = Idlestate.writer_idle) {

Type = "Write idle";

} else if (event.state () = = Idlestate.all_idle) {

Type = "All idle";

}

Ctx.writeandflush (Heartbeat_sequence.duplicate ()). AddListener (

Channelfuturelistener.close_on_failure); 3

System.out.println (Ctx.channel (). Remoteaddress () + "Timeout type:" + type);

} else {

Super.usereventtriggered (CTX, evt);

}

}

}

What to send when a heartbeat is defined

Determine if it is a idlestateevent event, and then handle

Send heartbeat content to client

Server

Server code is simple and listens on port 8082 after startup

Public final class Heartbeatserver {

static final int PORT = 8082;

public static void Main (string[] args) throws Exception {

Configure the server.

Eventloopgroup Bossgroup = new Nioeventloopgroup (1);

Eventloopgroup Workergroup = new Nioeventloopgroup ();

try {

Serverbootstrap B = new Serverbootstrap ();

B.group (Bossgroup, Workergroup)

. Channel (Nioserversocketchannel.class)

. option (Channeloption.so_backlog, 100)

. Handler (new Logginghandler (Loglevel.info))

. Childhandler (New Heartbeathandlerinitializer ());

Start the server.

Channelfuture f = b.bind (PORT). sync ();

Wait until the server socket is closed.

F.channel (). Closefuture (). sync ();

} finally {

Shut down all event loops to terminate all threads.

Bossgroup.shutdowngracefully ();

Workergroup.shutdowngracefully ();

}

}

}

Client Testing

The client uses the Telnet program that comes with the operating system:

Telnet 127.0.0.1 8082

Effect

20151106-heartbeat

Source

See Https://github.com/waylau/netty-4-user-guide-demos in Heartbeat bag

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Netty timeout mechanism and implementation of heartbeat program