1. Dortmund, 10 - 11 February 2003 Giorgia Lodi (lodig@cs.unibo.it)lodig@cs.unibo.it Department of Computer Science University of Bologna A.Amoroso,V.Ghini, N. Mezzetti, F. Panzieri

2. Dortmund, 10 - 11 February 2003 2 Summary System Model Auction Scenario J.J.J.: J2EE, JBOSS, JONAS QoS-Aware Containers Deployment phase Configuration Service Run Time Support Service References

3. Dortmund, 10 - 11 February 2003 3 System Model (1/2) An ASP can host different applications (e.g. auction application, video conference, games, etc…). Some applications might communicate with each other. The middleware platform, inside the ASP, consists of a group of Application Servers. The Application Servers communicate with each other. An application can consist of a certain number of components hosted by different Application Servers. The ASP is a cluster of different machines connected by a network and running possibly heterogeneous Operating Systems. In a single machine, more than one application server can be in execution concurrently (e.g. emulation of a cluster).

4. Dortmund, 10 - 11 February 2003 4 System Model (2/2) Application Server z Application Server b Application 1 Application 2 (Auction) Application 3 Application n … ASP Middleware Platform …. network …. Application Server a OSX Linux Solaris Pentium SparcPPC Application Server b Application Server c Application Server z

5. Dortmund, 10 - 11 February 2003 5 Auction Scenario (1/3) An end-user (seller, bidder) registers with an application owner (e.g. E-bay) by signing a contract. The contract entitles the end-user to use the auction application. The end-user may access the auction through HTTP requests and may use a piece of software which controls contract’s rights and obbligations. The application owner asks ASP (e.g. Adesso) for hosting the auction application: they establish a SLA between each other. The SLA can be described using SLAng, which is a notation generator. The ASP hosts the application providing a suitable platform through which the auction is executed.

6. Dortmund, 10 - 11 February 2003 6 Auction Scenario (2/3) The ASP may have a SLA with: - a SSP for using data storage resources. The SSP has a monitor used to control whether the SLA specifications are honoured - an ISP for using network resources. The ISP has a monitor used to control whether the SLA specifications are honoured. The ASP makes available a set of services/resources for running the application. The services/resources may communicate with each other using some protocol such as RMI/IIOP (possibly through WAN technology).

7. Dortmund, 10 - 11 February 2003 7 Auction Scenario (3/3) bidder seller E-BAY contract http request contract Tapas Plug-in Netscape Explorer SLA ASP RMI/IIOP Tapas platform RMI/IIOP SLAng SLA SSP SLA SLAng network ISP router DB Tapas monitor TTP CRA SLA CSP

8. Dortmund, 10 - 11 February 2003 8 J.J.J.: J2EE, JBOSS, JONAS J 2EE It uses a multitiered distributed application model. The application logic is divided into components according to function. Components make up the J2EE application. Components are installed in different machines depending on which tier the application component belongs to. J BOSS It is an open source application server. It integrates and develops a set of services for a full J2EE-based implementation. It is a microkernel based server and uses Java Management eXtension (JMX) for sofware integration. J ONAS It is a pure Java open source application server conforming to the J2EE specifications, as Jboss. ≠architecture (JMX), additional services.

9. Dortmund, 10 - 11 February 2003 9 J2EE: Platform tiers The platform provided is multitiered. Client tier components run on the client machine. Web tier and Business tier components run on the J2EE server. Web tier and Business tier form the Middleware tier. Data tier runs on the Enterprise Information System servers. Client machines, J2EE servers and EIS servers interact with each other using the network provided by an ISP.

10. Dortmund, 10 - 11 February 2003 10 J2EE: Containers A client tier component can be: - an application client running in an Application Container - a HTML client - a Java applet running in an Applet Container. HTML client and Java applet interact with Web components (e.g. servlets, JSPs) using some protocol (e.g. HTTP, SSL). Web Components run in a Web Container. Web Components and Java applications interact with EJBs through RMI/IIOP. EJBs (session beans, entity beans, message driven beans) run in an EJB Container.

11. Dortmund, 10 - 11 February 2003 11 J2EE: Services & Containers Every container is responsible for using the underlying middleware services (e.g. JMS, JTS, JAAS, JDBC, etc…). All these services rely on J2SE.New New services added in order to provide QoS-aware containers: - Configuration Service (CS) and Run Time Support Service (RTSS). CS and RTSS use group communication technology (e.g., Event Notification System (ENS)).

12. Dortmund, 10 - 11 February 2003 12 J2EE: Resource Adapter & Data Tier A Resource Adapter is a component running in any J2EE server that implements the J2EE Connector Architecture for a specific EIS. A Resource Adapter is analogous to a JDBC driver: they provide API in order to access a resource outside the J2EE server. Two types of “contracts” (i.e., APIs) implemented by a Resource Adapter: –Application Contract (A.C.) defines the API through which an EJB or a Web Component accesses the EIS –System Contract (S.C.) links the resource adapter to the connection, transaction and security services.

13. Dortmund, 10 - 11 February 2003 13 J2EE: QoS-aware Containers Client machine J2EE server EIS server Data tier EIS DB JDBC/SQLJ Proprietary protocol ISPISP Java application Application container HTML client Client tier Java applet Applet container J2SE RTSS plug-in Services HTTP HTTP,SSL Web tier Business tier servlet Web container JSP J2SEJ2SE CS RTSS RMI//IIOP J2SE EJB container Session Bean Entity Bean MDB CSRTSS RMI//IIOP JMS Resource Adapter RMI//IIOP Services ENS Services Managers Transaction Connection Security Resource Adapter J2SE CS RTSS ENS A.C. S.C.

14. Dortmund, 10 - 11 February 2003 14 The JBOSS JMX Microkernel JMX Implementation JTS/JTASecurity EJB ContainerDatabases Java Server Pages JMS Remote Management Data Sources RTSS CS

15. Dortmund, 10 - 11 February 2003 15 JONAS Architecture EJB ContainerWeb Container SB MDB EB Jonas J2EE Server JMXJMX EAREAR CSCS RTSSRTSS REGISTRYREGISTRY JMSJMS Servlets JSP Jadmin servlets DATABASEDATABASE DATABASEDATABASE JMXJMX WEBWEB MAILMAIL EJBEJB SECURITYSECURITY TR A NS A CT IO N

16. Dortmund, 10 - 11 February 2003 16 Packaging (1/2) J2EE components are packaged separately and bundled into a J2EE application for deployment. A J2EE application and each of its modules has its own deployment descriptor. A deployment descriptor is a XML document that describes a component’s deployment settings. An enterprise bean module deployment descriptor declares transactions attributes and security permissions for an enterprise bean. At run time, the J2EE server reads the deployment descriptor and acts upon the components accordingly.

17. Dortmund, 10 - 11 February 2003 17 Packaging (2/2) A J2EE application with all of its modules is delivered in an Enterprise Archive (EAR) file. An EAR file is a standard Java Archive (JAR). Each EJB JAR file contains a deployment descriptor, the enterprise bean files and related files. Each application client JAR file contains a deployment descriptor, the class files for the application client and related files. Each Web Archive (WAR) file contains a deployment descriptor, the Web component files and related resources.

18. Dortmund, 10 - 11 February 2003 18 Coding/Deploying/Running (Trust and QoS parameters derived from SLA).xml Files.class Application Developer ASP Deployer Deployment TAPAS Application Runner Configures environment Runs application (monitoring and adaptation) EAR Code Deployment Descriptors Parses Deployment Descriptors

19. Dortmund, 10 - 11 February 2003 19 Configuration Services (CS) (1/3) Local Resource Monitor getState() AS 1 AS 2 AS 3 SLS(A) Discovery Negotiation Reservation CS Discovery Negotiation Reservation CS getAvailability(SLS) reserve() getAvalability(SLS) Booking SLS(A): % Discovery Negotiation Reservation CS

20. Dortmund, 10 - 11 February 2003 20 Configuration Service (CS) (2/3) Discovery of available resources: –assess availability (e.g., load, network bandwidth, …) –Resource Monitor maintains state of local resources. CS –starts at application server start up time –is “enabled”, at deployment time, by: Object platform = enable_CS(SLS);

21. Dortmund, 10 - 11 February 2003 21 Configuration Service (CS) (3/3) Enabled CS, with input = SLS, declares itself as coordinator of the group of CSs. Discovery: –Coordinator sends a request for the availability to its peers using some method like: Object State = getAvailability(SLS); Negotiation: –Every CS books its own resources –CS produces an agreed QoS contract (i.e., contract between the application and the middleware platform). Reservation: –Coordinator confirms reservation of the resources. CS stopped with the following: disable_CS();

22. Dortmund, 10 - 11 February 2003 22 Run Time Support Service (RTSS) (1/2) It models the adaptive behaviour of our architecture. It requires the use of monitors. Monitors check the resource states as well as the requirements, within SLAs, to fulfill. A monitor, Resource Monitor, checks the resources and the QoS requirements. Resource Monitor maintains the resource states and the QoS requirements state in persistent objects. Persistent objects are used for producing log files, statistical analysis as well as irrefutable proofs. If it detects any changes, it may adopt some adaptive strategy to reconfigure the environment.

23. Dortmund, 10 - 11 February 2003 23 Run Time Support Service (RTSS) (2/2) Adaptive strategies may trigger a re-negotiation with the CS. –Callback mechanisms, through which communicate with the application (e.g. handlers at the application layer), used when no adpative strategies can be applied. Resource Monitor enabled using: Identity RM = enable_RM (CS, SLS, AgreedQoS); The RTSS stopped with: disable_RTTS();

24. Dortmund, 10 - 11 February 2003 24 References D.Lamanna, J.Skene and W.Emmerich ``SLAng: A Language for Defining Service Level Agreements'' London, January 2003. S.Bodoff, D.Green, E. Jendrock, M. Pawlan and B. Stearns ``The J2EE Manual'', Sun Microsystems Inc., 2001. B.Shannon "Java 2 Platform Enterprise Edition v.1.4" Sun Microsystem Inc., 2001. http://www.jboss.org/ http://www.objectweb.org/jonas/current/doc/JOnASWP.html W.Beckman, J.Crowcroft, P.Gevros and M.Oleneva ``TAPAS Deliverable D1'', University of Cambridge and Adesso AG, 2002- 10-17. Scott Stark and the Jboss Group ``JBOSS Administration and Development Second Edition'', Atlanta, USA, November 10 2002, Jboss Version 3.0.4. E. Checcet and J. Marguerite "JONAS v.2.4 Tutorial" Rice University INRIA, France.