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Subject: Re: how to correct stop a thread and avoid leaks
From: alexis <alzrck@gmail.com>
In-Reply-To: <4dee449b.0b610e0a.6050.ffffcf93@mx.google.com>
Date: Tue, 7 Jun 2011 12:38:59 -0300
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Message-Id: <1EA939D4-DD1C-408A-B0F2-B2017F2DF7B1@gmail.com>
References: <A9C3AD27-4783-40E1-8FD2-ACA5F751D3C1@gmail.com>
 <4dee449b.0b610e0a.6050.ffffcf93@mx.google.com>
To: Tomcat Users List <users@tomcat.apache.org>

yes, did that and it's working now. when contextDestroyed is called, i =
set the bool to false and force the loop out. What i was missing is loop =
is exited when=20
> if ((inputLine =3D in.readLine()) !=3D null)


this is completed, so, from Server class what i did is

Listener.requestStop(); // this causes to take the boolean to false to =
exit the loop
while(Listener.isAlive())
{
Thread.sleep(1500);
}

Causing main thread (Server) to wait, until a new message is processed =
by the in.ReadLine, then parsed, then exit the loop and close the =
Listener thread, and then Listener.isAlive() is not true anymore, now =
it's working perfect.


Thanks for the help.


On Jun 7, 2011, at 12:33 PM, Bill Miller wrote:

> If you want to work with threads in tomcat you need to know about the =
Tomcat
> org.apache.catalina.LifecycleListener interface. If you implement the =
interface and register your
> class within server.xml your class will be notified of Tomcat life =
cycle events (Start, Stop,
> etc...). You can then do appropriate things when those events happen.
>=20
> Here is an example method that is the only method in =
LifecycleListener:
> public class TomcatServerLifecycleListener implements =
LifecycleListener
> {
> 	public void lifecycleEvent(LifecycleEvent event)
> 	{
> 		if(Lifecycle.STOP_EVENT.equals(event.getType()))
> 		{
> 			//Call a method on your Runnable that will =
trigger it to exit the Run()
> method.=20
> 			// (or set a Boolean to stop looping, I've =
adjusted your code below too; how
> you
> 			// set the flag is up to you)
> 		}
> 	}
> }
> Here is the line to be added to Server.xml to register a class as a =
listener:
> <Listener =
className=3D"com.services.tomcat.TomcatServerLifecycleListener"/>
>=20
> So if you created an object like I have above and gave it a static =
method that allows you to insert
> an object that needs to be notified of a shutdown event, then you will =
be able to control your
> threads properly. You could even have your Runnable implement the =
LifecycleListener directly and
> have your registered object keep a list of objects that need to be =
notified.=20
>=20
> There are dozens of ways to do this, pick one that works for you. =
Don't forget to investigate all of
> the LifecycleEvent types in case you have use for the other options.
>=20
> Bill
>=20
> -----Original Message-----
> From: alexis [mailto:alzrck@gmail.com]=20
> Sent: June 6, 2011 8:10 PM
> To: Tomcat Users List
> Subject: how to correct stop a thread and avoid leaks
>=20
> Hello, im running an app that has a class that implements =
ServletContextListener (Server class), on
> that class i create a thread of Listener (that implements Runnable)
>=20
> Listener starts a ServerSocket that listen on a port, and in a =
periodically manner, this app
> receives a string, parses the string and stores the data inside a =
database. Flow is
>=20
> 1. receive a tcp connection (syn , syn+ack, ack)
> 2. receives lines over and over again inside this connections (each =
line is parsed and stored)
>=20
> Below is the code of Listener class and how i call this class from =
Server class. What im facing is
> im not able to stop Listener in a correct way. doing =
Listener.interrupt() does nothing. How can i
> safely stop Listener thread
>=20
>=20
> Thanks in advance
>=20
>=20
> --
> //initalize listener
>        Listener =3D new Thread((Runnable) new
> Listener(Integer.parseInt(prop.getProperty("listenonport"))));
>        if (!Listener.isAlive()) {
>            Listener.setName("ListenerThread");
>            Listener.setDaemon(true);
>            Listener.start();
>        }
>=20
> --=20
>=20
> package lesi.p1;
>=20
> import java.io.BufferedReader;
> import java.io.IOException;
> import java.io.InputStreamReader;
> import java.net.ServerSocket;
> import java.net.Socket;
> import org.apache.log4j.Logger;
>=20
> /**
> *
> * @author alz
> */
> public class Listener implements Runnable {
>=20
>    private static org.apache.log4j.Logger log =3D =
Logger.getLogger(Listener.class);
>    private Socket clientSocket =3D null;
>    private ServerSocket serverSocket =3D null;
>    private int listenport =3D 0;
>    Thread CDRThread =3D null;
>=20
>    public Listener(int port) {
>        this.listenport =3D port;
>    }
>=20
>    @Override
>    public void run() {
>        try {
>            log.debug("About to listen on port: " + this.listenport);
>            serverSocket =3D new ServerSocket(this.listenport);
>=20
>            while (true) {
>                clientSocket =3D serverSocket.accept();
>                CDRThread =3D new Thread((Runnable) new =
CDRExec(clientSocket));
>                if (!CDRThread.isAlive()) {
>                    CDRThread.setName("CDRThread");
>                    CDRThread.setDaemon(true);
>                    CDRThread.start();
>                }
>            }
>        } catch (IOException e) {
>=20
>            log.error("Catcher IOException: ", e);
>        } finally {
>            try {
>                log.info("Closing socket");
>                serverSocket.close();
>            } catch (IOException ex) {
>                log.error("Error trying to close port", ex);
>            }
>=20
>            if (CDRThread.isAlive()) {
>                log.info("Stopping CDRExec Thread");
>                CDRThread.interrupt();
>            }
>=20
>        }
>    }
>=20
>    class CDRExec implements Runnable {
>=20
> 	public Boolean keepRunning =3D true;	// !! Shutdown flag! Set =
to false to exit loop
>        private Socket client =3D null;
>=20
>        public CDRExec(Socket client) {
>            this.client =3D client;
>        }
>=20
>        @Override
>        public void run() {
>            String inputLine =3D "";
>            StringBuilder sb =3D new StringBuilder();
>            Parser p =3D null;
>            BufferedReader in =3D null;
>=20
>            log.debug("Thread: " + Thread.currentThread().getId() + " =
name: " +
> Thread.currentThread().getName());
>=20
>            try {
>                p =3D new Parser();
>                in =3D new BufferedReader(new =
InputStreamReader(client.getInputStream()));
>=20
>                while (keepRunning) {	// !! Use the shutdown flag =
instead of true
>                    if ((inputLine =3D in.readLine()) !=3D null) {
>                        p.parseCDR(inputLine);
>                    }
>                    inputLine =3D null;
>                }
>            } catch (IOException e1) {
>                try {
>                    in.close();
>                } catch (Throwable ignore) {
>                }
>                p =3D null;
>            }
>        }
>    }
> }
>=20
>=20
>=20
>=20
>=20
> ---------------------------------------------------------------------
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>=20


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