Thread management in servlet

Here is the problem that i am trying to solve - and get better understanding of issues to look out for.
1) Problem to solve
Clients sends an http request to an distributor server. The request contains a list of tasks. Each such task can be sent to a particular handling server (out of a known set) which can handle the request. Each task has a task type, which identifies which server the request needs to be passed to. The responses from the handler servers are then to be collected and passed back the client as a consolidated response.
On the distributor server, the servlet thread that is handling the request will
a. need to spread the requests for various handling servers
b. send the requests in parallel to handling servers
b. get all the responses , consolidate and send back
2)Proposed solution
I was thinking of having a thread pool - one thread for each handling server, initialized within servlet . When the distributor server receives a request - the tasks would be spread to these handling threads. The distributor thread would then wait, until the handling threads notify.
When a notification is received - the distributor thread will need to check if all responses are received. If not - it would need to wait (till a max_timeout) else return the response to client
3)Questions
- This involves waiting on the thread created by serlvet container (the distributor thread) and creating a threadpool. Thread creation and management by application in web-container is generally dissuaded - but given this issue - i see no other alternative
suggestions ? Its been a long email - thanks for considering
Fred

How many clients for the entry server do you presume for the application ? I ask this because it is very possible that the server to remain without available threads and give errors. If you use different servers for the final requests I suppose that are some very time consuming processes. What kind of application are running on these servers so that you want to use this kind of distributed computing ?
Why did you choose as an entry point a servlet container and http request for this kind of problem ? Do you need a graphic response in the browser ? If the response time is too long, the browser (Internet Explorer) will show exception and will not wait for the response (for this you must set some variabiles on client). Also the J2EE server must be set so that not to throw a time-out exception.
To prevent these, you could do so that not to block the distributor thread and let it send the answer back to the client. Then you can tell to client browser to query the server from time to time to check the status of the execution (you can do that from javascript). When the execution is ready you can retrun the response to the client. Doing this way you will not block the application server threads.
Now in the back end, you must somehow to take some identificators from the processes and sent them back to the client.
You can use a database to make the bridge between the central server and the other processes (here you can put the processes identificators). When the processes end up they update their results in the database.
The client, when will make the repetitive requests, will check the status of the processes in the database with given identificators.
Sounds like an interesting project.

Similar Messages

Weblogic's thread management

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Hi, I'm thinking on some issues related to Weblogic thread management.
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Hello all,
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Weblogic Thread Management

Hello Buddies,
We are facing performance problem in our J2EE application. For our application, Native Thread Management is enabled(EnableNativeIO=true).
But, while starting the weblogic server(managed server), we are getting the following message.
####<Oct 16, 2008 12:40:25 PM BST> <Warning> <Socket>
<wrohstsco10> <gc3-wrohstsco10>
<ListenThread.Default> <<WLS Kernel>> <>
<BEA-000402> <There are: 9 active sockets, but the maximum
number of socket reader threads allowed by the configuration is: 8. You
may want to alter your configuration.>
Can any one suggest on this?
Regards
Senthil Nathan M

you know that Native IO is enabled if you see "Native IO Enabled" in the server log at startup. This means that it founds the native IO shared libraries at startup.
You've probably already seen this, but this is from the WebLogic docs, at <http://e-docs.bea.com/wls/docs100/messages/Socket.html>
BEA-000402
Warning: There are: numSockets active sockets, but the maximum number of socket reader threads allowed by the configuration is: getMaxSocketReaders. You may want to alter your configuration.
Description
A non-native IO is being used, and the number of
socket reader threads is less than the number of active sockets.
Performance may degrade significantly. It is recommended that you
change the socket reader settings to improve the performance.
Cause
When non-native IO is used, IO is performed in a
blocking manner. Therefore, if the number of socket reader threads is
less than the number of active sockets, performance may degrade
significantly.
Action
Increase ThreadPoolPercentSocketReaders and/or
ThreadPoolSize, and/or decrease SocketReaderTimeoutMinMillis and/or
SocketReaderTimeoutMaxMillis.
This would imply what you understand. If you are seeing "Native IO Enabled" in your server log, but you are getting that warning, then I would first simply follow the advice in the message description that applies if you are using non-native IO. After experimenting with that (whether it works or not), I would file a support case asking first why you're getting that warning if you have native IO enabled, and whether following this advice for non-native IO should resolve your problem.

Threads spawning in Servlets allowed?

Hello to all servlet afficionados,
 I am following thread discussions already a while and there's always
 discussion whether to user threads or not (I am not talking about a
 servlet thread but about threads manually instantiated for other
 reasons like asynchroneous handling of tasks for loose coupling or for
 long running purposes).
 So here's my question:
 Is it definitely allowed to spawn threads from a servlet (and even put
 the reference into the application context to allow others to later on
 access that thread)?
 Does the jdk specify on this?
 Or Is it even specific for each servlet engine? What is BEA saying
 about this?
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 include an ejb-container? Again, does the specification say something
 about this? What does BEA say about this?
 Thanks for trying to find out the real truth :-)
 regards
 Stefan


Stefan,
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 of threads within a servlet, but most will tell you that you should avoid it
 if possible. Having said that, I've seen quite a few implimentations that
 use background threads for tasks such as log queue processing and have not
 really had any issues. To me it's a matter of degree. As long as your
 architecture makes sense and you are careful to avoid potential deadlocks,
 you should be ok. FWIW, BEA recommends not creating threads within a web
 application.
 -chris
 "Stefan Hoehn" <[email protected]> wrote in message
 news:[email protected]...
 > Hello to all servlet afficionados,
 >
 > I am following thread discussions already a while and there's always
 > discussion whether to user threads or not (I am not talking about a
 > servlet thread but about threads manually instantiated for other
 > reasons like asynchroneous handling of tasks for loose coupling or for
 > long running purposes).
 >
 > So here's my question:
 >
 > Is it definitely allowed to spawn threads from a servlet (and even put
 > the reference into the application context to allow others to later on
 > access that thread)?
 >
 > Does the jdk specify on this?
 >
 > Or Is it even specific for each servlet engine? What is BEA saying
 > about this?
 >
 > And even further: Is this different on application servers that
 > include an ejb-container? Again, does the specification say something
 > about this? What does BEA say about this?
 >
 >
 > Thanks for trying to find out the real truth :-)
 >
 > regards
 > Stefan

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Dr clap
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J2EE specification.
"""

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I am involved in building an application using using Oracle9i App server, IBM MQSeries message queueing and Enterprise Java beans (to name a few things).
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          Hi all,
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          I am testing with 60 concurrent users.
          I have set the database connection pool minimum capacity to 50, capacity increment
          to 10 and maximum capacity to 100.
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oc4j/orion is the fastest servlet engine on the planet. Those
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www.elephantwalker.com

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Sandeep Rajpathak wrote:
I am using WebLogic5.1.0 version wherein I am registering a Servlet which
would be called by all the clients connecting
to my aplication. The servlet's service methods is taking some time to
execute. Since the servlet is following a SingleThreadModel, when there are
a large number of Clients connected, the number instances of Servlets
created are very high and the number of thread in the Application Server
process becomes very high affecting the performance of the other
applications.
Is it possible to restrict the number of instances of the servlets that get
created in the Application server ?
What are the setting required to achieve this ?
Sandeep--
Michael Young
Developer Relations Engineer
BEA Support

A Thread manages a connection from the outside--help me to finish it

**RUN THIS CODE AND HELP ME--- THANKS A LOT**
EchoClient is thread which manage a connection from the outside.
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Random;
public class EchoClient extends Thread {
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     private Socket manageSocket = null;
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     private BufferedReader in;
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     private int count;
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            //private ClientNode[] clientArray = new ClientNode[9999];
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               listenSocket = new ServerSocket(903);
               manageSocket = listenSocket.accept();
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                    in = new BufferedReader(new InputStreamReader(manageSocket
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                    out = new PrintWriter(manageSocket.getOutputStream());
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                         count++;
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}And a Login Frame which will send to server a varialble (CONNECTING) which requires to connect and keep waiting for a variable to Open a ChatFrame with a new port
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
public class Login extends JFrame {
     public ChatFrame chatFrame;
     private final int CONNECTED = 1;
     private final int CONNECTING = 11;
      * @param args
     public Login() {
          // TODO Auto-generated method stub
          setSize(50, 150);
          JButton loginButton = new JButton("Login");
          JPanel p = new JPanel();
          p.setLayout(new FlowLayout());
          p.add(loginButton);
          add(p);
          loginButton.addActionListener(new ActionListener() {
               @Override
               public void actionPerformed(ActionEvent e) {
                    loginServer();
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          try {
               Socket connectSocket = new Socket("127.0.0.1", 903);
               while (true) {
                    BufferedReader in = new BufferedReader(new InputStreamReader(
                              connectSocket.getInputStream()));
                    PrintWriter out = new PrintWriter(connectSocket
                              .getOutputStream());
                    out.print(CONNECTING);
                    System.out.println("At here");
//(***position***)
                    int line = in.read();
                    System.out.println("At here1");
                    if (line == CONNECTED) {
                         int port = in.read();
                         chatFrame = new ChatFrame(port);
                         chatFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                         chatFrame.show();
                         connectSocket.close();
          } catch (Exception exp) {
               exp.printStackTrace();
     public static void main(String[] args) {
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          login.show();
          login.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}and this is ManageClient Thread...
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class ManageClient extends Thread {
     private ServerSocket ssClient;
     private Socket sClient;
     private int port;
     public ManageClient(int port) {
          this.port = port;
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          return port;
     public void run() {
          try {
               ssClient = new ServerSocket(getPort());
               sClient = ssClient.accept();
               while (true) {
                    BufferedReader in = new BufferedReader(new InputStreamReader(
                              sClient.getInputStream()));
                    PrintWriter out = new PrintWriter(sClient.getOutputStream());
                    String s = in.readLine();
                    if (s != null)
                         out.print("have recieved");
          } catch (Exception e) {
               e.printStackTrace();
}my problem...
At firts EchoClient will run.. and then Login but when I click to the Login button it has just only did before int line = in.readLine();(*** postion ***)
I don't know why it doesn't continue. It stops here and the login button is still visible(cause code has not finish)..
That's my problem...
Somebody help me
Edited by: rockfanskid on Oct 17, 2007 4:25 AM

Somebody helps me to finish this project...
thanks for racing this thread

Thread management in servlet

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