I want to let you know that since the release of Caucho Resin 4.0, Atmosphere applications can be deploy on Resin and will be supported natively. Resin 4.0 implements Servlet 3.0.

That’s really good. Another web server that is supported.

What about the Websocket’s Caucho implementation… nah ! There implementation is too buggy right now. I suppose the code it using a early release of the Websocket specs, and never updated it. Anyway, Websocket application won’t work on Resin 4.0

We posted a thread on there forum here : http://forum.caucho.com/showthread.php?t=10680

but still didn’t received news from them. So until they fix it, I suggest that you try your Websocket application on another web server like Glassfish.

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Just a little note that we try to add Websphere native support for Atmosphere. We work really hard to find an API that could allow us to do that, but is simply impossible.

We were able to get in touch with the dev team of Websphere and the dev team of WebSphere Application Server Feature Pack for Web 2.0. They have demo that used bayeux for comet application or JMS to simulate asynchronous connections, but it’s not a complete asynchronous solution.

Even with the addon WebSphere Application Server Feature Pack for Web 2.0, you can’t suspend and resume a connection. Websphere server doesn’t support that. It’s not supported in WAS 7.0, but in 8.0 alpha there should be Servlet 3.0 support.

Until IBM do something about that, or wait for WAS 8.0, you will still be able to deploy Atmosphere application on WAS but it will use BlockingIO (one blocking thread by connection).

If that is not enough for you, I suggest Glassfish as alternative. Of course, we will continue to monitor the situation. Maybe the community call could be enough to wakeup them

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Just to let you know that Grizzly Deployer was adopted (almost) by another framework : Akka.

Since May 22, 2010, viktorklang is working in a branch : deployer. here the description in the commit “Starting to add Deployer [viktorklang]”

You can browse the code on github : http://github.com/jboner/akka/tree/deployer/akka-core/

I hope to see that included in a next release.

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Just to let you know that Grizzly Deployer was adopted by another framework : Atmosphere.

Since Atmosphere-0.6, Grizzly Deployer is in the module : spade-server

To launch Atmosphere application you could use Grizzly Deployer or use Atmosphere-Spade-Server (that used Grizzly Deployer under the hood).

You can browse the changes on github : http://github.com/Atmosphere/atmosphere/tree/master/extras/spade-server

I did the commit under the name “Unknown” It was my first git commit.

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It has been a while since a blog about Grizzly, I was too busy adding new features. The Grizzly Deployer’s community grows and requested theses new features.

Here a quick list of the changes :

• Websockets support
• Watch folder
• Can starts without applications to deploy
• Can be embedded and extended easily
• and few bug fixes (thanks to the community)

A little overview or remainder of what is Grizzly Deployer

Grizzly Deployer is a bundle of Grizzly project that act as a web container. It will allow you to deploy applications (war, servlet).
Works fine for Comet, Atmosphere, JSP applications … For more details, I suggest this link Introduction to the first release of Grizzly Deployer

First, lets take a look at the command line parameters.

Usage: com.sun.grizzly.http.servlet.deployer.GrizzlyWebServerDeployer

  -a, --application=[path]    Application(s) path(s).

                              Application(s) deployed can be :
                              Servlet(s), war(s) and expanded war folder(s).
                              To deploy multiple applications
                              use File.pathSeparator

                              Example : -a /app.war:/servlet/web.xml:/warfolder/

  -p, --port=[port]           Runs Servlet on the specified port.
                              Default: 8080

  -c, --context=[context]     Force the context for a servlet.
                              Only valid for servlet deployed using
                              -a [path]/[filename].xml

  --dontstart=[true/false]    Won't start the server.
                              You will need to call the start method.
                              Useful for Unit testing.
                              Default : false

  --libraryPath=[path]        Add a libraries folder to the classpath.
                              You can append multiple folders using
                              File.pathSeparator

                              Example : --libraryPath=/libs:/common_libs

  --autodeploy=[path]         AutoDeploy to each applications.
                              You could add JSP support.
                              Just add a web.xml that contains Jasper

                              Example : --autodeploy=/autodeploy

  --webdefault=[path]         webdefault to be used by all applications, can be file or dir with multipe web.xmls.
                              If you want to add only one webdefault point it to web.xml file,
                              If you want multiple files to be included put them in one dir and provide this location here.

                              Example : --webdefault=webdefault.xml

  --cometEnabled=[true/false] Starts the AsyncFilter for Comet.
                              You need to active this for comet applications.
                              Default : false

  --websocketsEnabled=[true/false] Starts the AsyncFilter for Websockets.
                              You need to active this for websockets applications.
                              Default : false

  --forceWar=[true/false]     Force war's deployment over a expanded folder.
                              Will deploy the war instead of the folder.
                              Default : false

  --ajpEnabled=[true/false]   Enable mod_jk.
                              Default : false

  --watchInterval=[seconds]   Watch interval to scan for new applications to deploy in work folder.
                              Default : -1 ; disabled

  --watchFolder=[path]        Folder to scan for new applications to deploy in work folder
                              Default : none

Websocket support

The first feature added was Websockets support. It can be enabled at command line by using the parameter –websocketEnabled=true . That will allow you to deploy Websocket applications.

Watch folder

This feature is interesting, because most of the web container have it. Grizzly Deployer will watch a specific folder to applications to deploy. When this feature was added, I remove the need to specify a application to deploy by command line.
To enable this feature you need to use the command line parameter –watchFolder=[path]. It can be used with this other parameter : –watchInterval=[seconds].

The parameter –watchInterval is used to create a watchdog that will monitor the watch folder. If the parameter –watchInterval is not present, when Grizzly Deployer starts, it will check
all applications that are in the watch folder at launch time and will deploy them, but it won’t monitor the folder after that.

When both of theses parameters are used, it will create a watchdog that will deploy and undeploy application put in the watch folder, and remove from that folder. If you deploy an application at command line and put another application with the
same context name in the watch folder, the application in the watch folder won’t be deploy twice.

Embedded Grizzly Deployer

Grizzly Deployer could already be embedded trough his API, but we got few feedback about to make it simplier. The problem wasn’t the API, it just that most people will only use the main part of Grizzly Deployer : deploy a war.

So to make it easier and faster to implement, I did a little refactoring. We now have 2 main config classes we could use to launch an Embedded Grizzly Deployer : DeployerServerConfiguration and DeployableConfiguration.

DeployerServerConfiguration

That file is used to launch Grizzly Deployer. It contains the same command line parameters. In fact, at runtime, the command line parser use that classe.

    GrizzlyWebServerDeployer deployer = new GrizzlyWebServerDeployer();
    
    DeployerServerConfiguration conf = new DeployerServerConfiguration();
    conf.cometEnabled = true;
    conf.watchFolder="C:/temp/webapps/";
    conf.watchInterval=15;
    deployer.launch(conf);                             

Once grizzly Deployer is launched in your application, you can deploy a war later. For that, you use this class : DeployableConfiguration.

    DeployableConfiguration warConfig = new DeployableConfiguration();  
    warConfig.location = "C:/temp/webapps/grizzly-jmaki.war";
    
    deployer.deployApplication(warConfig);                           

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CONTEXT

I want to share a problem that we had in our project. We were doing a real-time “Profits and Loss” server (P&L). The server sends stock updates to all the users subscribed to the stocks, basically as Google Finance or Yahoo Finance.

SIMPLE IMPLEMENTATION

I will used a basic approach (no aggregation and no optimization) to explain the problem that we had with Serialization and Hessian.

The server always keep the last value on the stocks, because when a user ask for a quote we want to send back as soon as possible the
last value (from the cache) that we had on that stock).

We kept the stock prices (BID and ASK) in a simple object : SymbolSerializable.

When a update is received for a stock, we update the values in his SymbolSerializable and send back the updated values to all
client subscribed to this stock.

...

symbol.setBid(update.getBid());
symbol.setAsk(update.getAsk());

...

for(Client client : clientList){
    client.sendUpdate(symbol);
}

....

It can’t be more simpler than that. The client will received each updates on his stocks.

The problems that we had was surprising. The clients were receiving the always the same price on a stock !

WHY ?

here an example :

stock : ABC

Updates :

1 : bid=10.25$, ask=10.50$
2 : bid=11.50$, ask=11.75$
3 : bid=12.00$, ask=12.15$

and the clients received :

1 : bid=10.25$, ask=10.50$
2 : bid=10.25$, ask=10.50$
3 : bid=10.25$, ask=10.50$

To debug our server we printed the values sent to the client, and we saw in the server’s logs that the values were corrects.

value sent to client :
bid=10.25$, ask=10.50$

value sent to client :
bid=11.50$, ask=11.75$

value sent to client :
bid=12.00$, ask=12.15$

Everything look fine, why it doesn’t work on the client side ?

INVESTIGATION/SOLUTION

The only thing that could cause the problem were our Serialization in the server.

I’ll show you four different test cases. See the implementations below.

• #1 : Reference implementation using Serializable (failed)
• #2 : Changed Serializable for Externalizable interface (failed)
• #3 : Serializable using new (passed)
• #4 : Serializable using reset (passed)

Here the Serializable pojo

package ca.sebastiendionne.demo.model;

import java.io.Serializable;

public class SymbolSerializable implements Serializable {

    private static final long serialVersionUID = 7853892880704628717L;

    Double bid = null;
    Double ask = null;

    public SymbolSerializable(){
    }

    public Double getBid() {
        return bid;
    }
    public void setBid(Double bid) {
        this.bid = bid;
    }
    public Double getAsk() {
        return ask;
    }
    public void setAsk(Double ask) {
        this.ask = ask;
    }

    @Override
    public String toString() {
        return "bid = " + bid + "  ask=" + ask;
    }

}

Here the Externalizable pojo

package ca.sebastiendionne.demo.model;

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

public class SymbolExternalizable implements Externalizable {
    private static final long serialVersionUID = 1853892880704628717L;

    Double bid = null;
    Double ask = null;
    
    public SymbolExternalizable(){
        
    }
    
    public Double getBid() {
        return bid;
    }
    public void setBid(Double bid) {
        this.bid = bid;
    }
    public Double getAsk() {
        return ask;
    }
    public void setAsk(Double ask) {
        this.ask = ask;
    }
    
    @Override
    public String toString() {
        return "bid = " + bid + "  ask=" + ask;
    }

    @Override
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        bid = (Double)in.readObject();
        ask = (Double)in.readObject();
    }

    @Override
    public void writeExternal(ObjectOutput out) throws IOException {
        out.writeObject(bid);
        out.writeObject(ask);
    }
    
}

For the test cases I use a for loop to create Symbol and serialized on the hard drive and unserialized them back.

Here the code for the test case #1 (used as reference)

package ca.sebastiendionne.demo;

import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import ca.sebastiendionne.demo.model.SymbolSerializable;

public class SerializationFailed {

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception {
        
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File("test.ser"))); 
        
        
        SymbolSerializable symbol = new SymbolSerializable();
        
        // dummy values
        symbol.setAsk(new Double(-1));
        symbol.setBid(new Double(-1));
        
        for(int i=0;i<10;i++){
            // update values
            symbol.setAsk(new Double(i));
            symbol.setBid(new Double(i));
            
            oos.writeObject(symbol);
            oos.flush();
        }
        
        oos.flush();
        oos.close();
        
        // read
        
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("test.ser")));

        try {
            Object obj = null;
            while((obj = ois.readObject())!=null){
                System.out.println((SymbolSerializable)obj);
            }
        } catch (EOFException e) {
            System.out.println("All items read");
        } catch(Exception e){
            e.printStackTrace();
        } finally {
            ois.close();
        }
        
        
    }

}

Here the code for the test case #2

package ca.sebastiendionne.demo;

import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import ca.sebastiendionne.demo.model.SymbolExternalizable;

public class SerializationFailed2 {

    
    /**
     * @param args
     */
    public static void main(String[] args) throws Exception {
        
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File("test.ser"))); 
        
        
        SymbolExternalizable symbol = new SymbolExternalizable();
        
        // dummy values
        symbol.setAsk(new Double(-1));
        symbol.setBid(new Double(-1));
        
        for(int i=0;i<10;i++){
            // update values
            symbol.setAsk(new Double(i));
            symbol.setBid(new Double(i));
            
            oos.writeObject(symbol);
            oos.flush();
        }
        
        oos.flush();
        oos.close();
        
        // read
        
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("test.ser")));

        try {
            Object obj = null;
            while((obj = ois.readObject())!=null){
                System.out.println((SymbolExternalizable)obj);
            }
        } catch (EOFException e) {
            System.out.println("All items read");
        } catch(Exception e){
            e.printStackTrace();
        } finally {
            ois.close();
        }
        
        
    }

}

Here the code for the test case #3

package ca.sebastiendionne.demo;

import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import ca.sebastiendionne.demo.model.SymbolSerializable;

public class SerializationWithNew {

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception {
        
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File("test.ser"))); 
        
        
        SymbolSerializable symbol = new SymbolSerializable();
        
        // dummy values
        symbol.setAsk(new Double(-1));
        symbol.setBid(new Double(-1));
        
        for(int i=0;i<10;i++){
            // update values
            symbol.setAsk(new Double(i));
            symbol.setBid(new Double(i));
            
            SymbolSerializable symbol2 = new SymbolSerializable();
            symbol2.setAsk(symbol.getAsk());
            symbol2.setBid(symbol.getBid());
            
            oos.writeObject(symbol2);
            oos.flush();
        }
        
        oos.flush();
        oos.close();
        
        // read
        
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("test.ser")));

        try {
            Object obj = null;
            while((obj = ois.readObject())!=null){
                System.out.println((SymbolSerializable)obj);
            }
        } catch (EOFException e) {
            System.out.println("All items read");
        } catch(Exception e){
            e.printStackTrace();
        } finally {
            ois.close();
        }
        
        
    }

}

Here the code for the test case #4

package ca.sebastiendionne.demo;

import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import ca.sebastiendionne.demo.model.SymbolSerializable;

public class SerializationWithReset {

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception {
        
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File("test.ser"))); 
        
        
        SymbolSerializable symbol = new SymbolSerializable();
        
        // dummy values
        symbol.setAsk(new Double(-1));
        symbol.setBid(new Double(-1));
        
        for(int i=0;i<10;i++){
            // update values
            symbol.setAsk(new Double(i));
            symbol.setBid(new Double(i));
            
            oos.writeObject(symbol);
            oos.flush();
            oos.reset(); // magic line
        }
        
        oos.flush();
        oos.close();
        
        // read
        
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("test.ser")));

        try {
            Object obj = null;
            while((obj = ois.readObject())!=null){
                System.out.println((SymbolSerializable)obj);
            }
        } catch (EOFException e) {
            System.out.println("All items read");
        } catch(Exception e){
            e.printStackTrace();
        } finally {
            ois.close();
        }
        
        
    }

}

I can't say what is the performance impact if we use reset() on each updates sent. It is better to use new or reset ?

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