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:

PublicClassHeartbeathandlerinitializerExtendschannelinitializer<channel> {PrivateStaticFinalint read_idel_time_out =4;Read timeoutPrivateStaticFinalint 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}}             

1. Use Idlestatehandler to set the time for read and write timeouts
2. Defines a Heartbeatserverhandler processor that is used to handle timeouts when the heartbeat is sent

Defines a heartbeat processor

PublicClassHeartbeatserverhandlerExtendsChannelinboundhandleradapter {Return a unreleasable view on the given bytebufWhich'll just ignore release and retain calls.PrivateStaticFinal Bytebuf heartbeat_sequence = unpooled. Unreleasablebuffer (Unpooled.copiedbuffer ("Heartbeat", Charsetutil.utf_8));1@OverridePublicvoidUsereventtriggered(Channelhandlercontext ctx, Object evt)Throws Exception {if (evtInstanceof 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);}}}   

1. What to send when a heartbeat is defined
2. Determine if it is a idlestateevent event, and then handle
3. Send heartbeat content to client

Server

Server code is simple and listens on port 8082 after startup

PublicFinalClassHeartbeatserver {StaticFinalint PORT =8082;PublicStaticvoidMain(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, + ). 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.shut Downgracefully (); } }}

Client Testing

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

telnet 127.0.0.1 8082

Effect

Transfer from Http://waylau.com/netty-time-out-and-heartbeat/?utm_source=tuicool&utm_medium=referral

Netty timeout mechanism and implementation of heartbeat program