AgentScape Forum

New release AgentScape 2 Milestone 3 in AgentScape : Announcements

Mon, 02 May 2011 11:31:12 +0200

A new release of AgentScape has just been released: Agentscape 2 Milestone 3 (r5088).
You can download this release from the sidebar or from the downloads page.

This 'Milestone 3' version includes bug fixes & updates to the core middleware, as well as a number of new & improved features such as Web Service Gateway, a new configuration mechanism, and initial support for security mechanisms. For more information about the updates, see here.

This release is not compatible with AgentScape 0.9.x.

A summary of some of the main changes are:

- Web-Service Gateway
- Distributed Naming and Directory service
- Security Architecture
- XML-based AgentScape configuration mechanism
- New AgentScape administration API
- Bug-fixes and documentation

You can download this release from the sidebar or from the downloads page.

Getting the instance of an agent in AgentScape : Trouble Shooting

Fri, 11 Mar 2011 16:19:10 +0100

My project is creating a web application, which provides information, dynamically from a number of sources.

The reason of using AgentScape, was the data collection and processing seemed to fit well into agents.

However, there didn't seem to be a good way to deliver this information to a web-page: Servlets provide a web-interface for an agent, but I need an agent to serve the entire web application: multiple pages, and I wanted the urls of these pages to be relatively intuitive for the user, and the existence of the agents to be invisible.

The Play! framework provides a REST interface and an MVC structure for web applications. This seemed to fit well, as the agents can then simply serve the data to the framework, to generate the models, and then create the web pages from these models.

As a result, Play! has effectively become a manager within my system, which creates agents to collect, serve and process information. It then communicates with these agents, getting them to perform tasks (such as storing data), and gets responses from them (such as models).

At the moment, using the AgentScapeApi, this is all working fine, however the desire is that the Play! component of my application could be incorporated into AgentScape (or vice-versa), so that they could be installed as one.

Furthermore, by having it as a service, it would become location independent, and, theoretically, we could have multiple instances of the Play! server, to distribute load, if it had to deal with many requests.

The issue, however, is Services do not fit well with my overall structure, as this component has become more of a manager; creating agents and communicating with them.

Could all this be achieved by somehow making it an agent, that happens to have a REST interface to the web? Or is there another way? Or is it simply not going to be possible to combine these 2 components any more than using the AgentScapeApi?

Many Thanks

Sam

Getting the instance of an agent in AgentScape : Trouble Shooting

Tue, 08 Mar 2011 15:10:57 +0100

Hello Sam,

the reasons why servlets are able to work with information from the instance of the agent is that we especially made the service this way. But this wasn't exactly easy to do (it involved a number of callbacks from service -> agent). Still, it is possible to do so.

If you can create a service which serves your agents with information (models, etc) which can be obtained by an agent on demand (request-response) this is a lot easier, provided these models can be easily copied from one JVM to another.

Personally I also do not know much about the Play! framework, but it seems interesting. Maybe you could elaborate more on what your ideas about the application structure and functionality are? I am not entirely sure how Play! and AgentScape would be able to interact. What are your ideas about this?

Cheers,
Reinier

Can't send or receive messages directly after injecting agent in AgentScape : Trouble Shooting

Tue, 01 Mar 2011 15:09:30 +0100

I have found out the problem.

In my agent I do;

URL url = new URL(this.getArgs()[1]);
InputStream stream = url.openStream();

Thus I created the deadlock myself: the server is blocking, receiving a message, and the client is blocking, trying to get the xml from the server.

Thanks for your help

Sam

Can't send or receive messages directly after injecting agent in AgentScape : Trouble Shooting

Mon, 28 Feb 2011 15:34:09 +0100

Hi Sam,

I don't know how you start your agents, but this works for me with AgentScape2:
(forgive me the bad coding :-) )

Code:

public class Main extends Agent {

    public static void main(String[] args) throws Exception {

        AgentScapeApi api = AgentScapeClient.getAgentScapeClient();

        Class2Jar c2j = new Class2Jar();
        c2j.add( Main.class );

        byte[] jar = c2j.getJar();

        AgentArchive aa = AgentArchive.fromJar(jar);

        AgentInfo info = api.startAgent( new AgentScapeID("loc"), aa);

        System.out.println("Waiting for message");
        Envelope e = api.receiveMessage(info.getOwnerHandle(), true);
        System.out.println("Got message " + e.getData());

        System.out.println("Sending message");
        Envelope e2 = new Envelope( info.getPrimaryHandle(), info.getOwnerHandle(), "stop message" );
        api.sendMessage(e2);
        System.out.println("Done sending message " );
    }

    @Override
    public void run() {

        Envelope e = new Envelope( getOwnerHandle(), getPrimaryHandle(), "test message");
        try {
            System.out.println("Agent: Sending message");
            this.sendMessage(e);

            System.out.println("Agent Waiting for message");

            e = this.receiveMessage(true);

            System.out.println("Agent Got message " + e.getData() + " ... quitting");
        } catch (Exception ex) {
            System.err.println("Error sending message " + ex);
        }
    }
}

Compile this code into one jar file.

Then start up a location called "loc":

Code:

java -jar lib/asstartup.jar loc

Then run your jarfile with java -jar (and set your classpath if necessary)

Bye,
Michel

Getting the instance of an agent in AgentScape : Trouble Shooting

Mon, 28 Feb 2011 14:42:39 +0100

Hi Sam,

I'm afraid I don't know the Play! component so my help is maybe of little use.
I'll have a talk with Reinier about this as well, and then get back to you.

Bye,
Michel

Getting the instance of an agent in AgentScape : Trouble Shooting

Mon, 28 Feb 2011 12:48:38 +0100

Any thoughts on this?

Many Thanks

Sam

Can't send or receive messages directly after injecting agent in AgentScape : Trouble Shooting

Sat, 26 Feb 2011 22:14:46 +0100

Hi There,

I am having a problem, when I try and inject an agent in code, and the receive a message. Not only does it fail to receive the message, but the agent is not actually injected. However there are no exceptions; it just hangs.

I have tried doing Thread.sleep, but this seems to delay the injection of the agent, even though I am sleeping after .startAgent(...

The only method I have found to overcome this is by putting one of the methods in another thread, but then calling thread.join() causes the issue to appear again.

The same problem occurs if I try and inject and then send an agent.

It seems like the 2 calls (to agentScapeApi) are conflicting and somehow conflicting with Thread.sleep too.

Any help would be much appreciated

source code in AgentScape : General Discussion

Sat, 26 Feb 2011 10:50:31 +0100

Thanks for the support.
0.9.3 installer works just fine.

Getting the instance of an agent in AgentScape : Trouble Shooting

Thu, 17 Feb 2011 17:11:56 +0100

Hi Michel,

Thanks for the quick response.

Yes, I realise that wanting direct access to the agent was wrong; I had just been looking at servlets and wanted the same direct access in Play! Using messages will indeed be fine. I imagine only needing copies of the models, or sending requests to update, so simple messaging will be OK, potentially with method-invocation.

After discussing this issue with Julian, we were considering the possibility of making this Play! component into a Service, as it will effectively become a 'manager', creating, maintaining and communicating with agents (using the AgentScapeApi). This would enable it to be installed as part of AgentScape and would potentially allow multiple Play! Services at different Locations, linked by the Location Manager.

Do you have any thoughts/advice on if this seems like a sensible idea?

Many Thanks
Sam

Getting the instance of an agent in AgentScape : Trouble Shooting

Thu, 17 Feb 2011 16:42:25 +0100

Hi Sam,

The idea of agents is that they are autonomous, so there is a reason why you cannot get a direct
reference to the Agent instance itself. You only get its handle, so you can sent messages (requests)
to the Agent who can then reply on your request.

So, one way to get the models is to use the owner handle and primary handle you get when you create
the agent to sent it a request and the agent can then sent the model back to the caller.

However, this way you will not get `direct' access to the models inside the agent, so if you need
to manipulate the models directly (and not just get a copy of the model) then you need something else.

One way would be to use servlets to access/update the models, or you could implement a more
elaborate request/reply mechanism using the messages you can sent to agents. In fact you would implement
a kind of method-invocation over AgentScape messages, which is what agents already use in the form of
the AgentProxy mechanism.

Hope this helps you out a little more.
Bye,
Michel

Getting the instance of an agent in AgentScape : Trouble Shooting

Wed, 16 Feb 2011 18:22:22 +0100

Hi There

I am developing a web application using AgentScape and the Play! framework (an MVC model).

Currently, when a user hits the root of my application, an agent is dynamically created to serve that client. The aim is that this agent will generate the Models required for the agent, given their context and information in an RDF database. These models could then be accessed by the controllers within the main application, and used to generate the html and json views.

The problem however, is when I programatically inject my agent, I am only given its handle; not the instance of that agent. As a result, I have no way to access the models held within that agent.

Is there any way around this?

(I ideally want to avoid servlets, so that the urls for the application are more user friendly, and feel that the MVC model is a good solution to presenting the data held within the agent)

Many Thanks

source code in AgentScape : General Discussion

Wed, 09 Feb 2011 11:05:57 +0100

Hi Mike,

The sources are included in the 0.9.3 installer jar, available from the agentscape website.
Just run the installer: java -jar AgentScape-0.9.3.jar
and select the option to install the sources when asked.

Bye,
Michel

source code in AgentScape : General Discussion

Wed, 09 Feb 2011 01:54:38 +0100

I note that the 0.9.3 release includes no source code. Is the source available?

Thanks,
--Mike

Monitoring Agent Interactions in AgentScape : General Discussion

Mon, 31 Jan 2011 23:11:23 +0100

Okay, sure thing. Thanks Michel.