A Style-Aware Architectural Middleware for Resource-Constrained, Distributed Systems

1. A Style-Aware Architectural Middleware for Resource-Constrained, Distributed Systems CS 5381 Steven Ruiz Authors: Sam Malek, Marija Mikic-Rakic, and Nenad Medvidovic

2. Table of Contents • Introduction • Objectives • Middleware Design • Prism Setting Support • Architectural Support • Evaluation

3. Introduction • Software Systems are increasingly moving from desktop to the mobile setting • Programming in the small and many (Prism) • Properties: Highly Constrained Resources • Limited power • Low network bandwidth • Slow CPU speed, limited memory • Small display size

4. PrismMW • Programming in the Large (PitL) • Suited mainly for desktops • Middleware • Developed to support the implementation of Software Arch. in Prism setting • Provides architecture level concepts • Component • Connector • Configuration • Events

5. Key Contributions • Employs a separation of concern • Provides: • Flexibility • Efficiency • Size, speed, overhead • Scalability • Number of components, connectors, events, threads, hardware devices • Extensibility • Support for new development concerns

6. Prism Goals • Investigate the following issues: • Mobile device limits (power, size, memory, ..) • Modeling • Analysis • Simulation • Prism characterized by Proprietary OS’s (Palm, Symbian) • Tie in Prism with Software architecture (architecture-based development)

7. Objectives (Support) • Provide native support for designing & implementing architectural abstraction • Should accommodate system development based on different styles • Address the main parts of arch. based design/implementation and middleware

8. Objectives (Small & Many) • Enable efficient execution of apps on platforms with different characteristics • Extend support for access of shared hardware • Scalable • Large set of devices • Execution Threads • Components, connectors, communication • Extensible & Configurable • Accommodate varying development concerns • Multiple Arch. Styles

9. Example Application • TDS (Troops Deployment & Simulation) • Distributed deployment of personnel • Headquarters • Gathers info from field & displays current battlefield status • Networked via secure links to PDA’s • Commanders • Connected to soldiers • Give orders to soldiers • Soldiers • View segment of battlefield & receive orders

10. TDS Components • Map • Model of system resources (terrains, tanks,..) • Repository • Stores map resources • StrategyAnalyzerAgent • Analyze deployment of friendly troops • DeploymentAdvisor • Suggests deployments of troops • SimulationAgent • Simulates outcomes

11. Prism Core • 12 classes, 4 interfaces • Limited direct dependencies • Brick Class • Abstract class representing architectural building blocks • Scaffold Class (associated with every Brick) • Schedules and queues events for delivery • Pools execution threads used for event dispatching • Allows most suitable event scheduling • Architecture Class • Records the configuration of its constituent components, connectors, ports, and provides removal capability • Event • Captures communication in an architecture

12. Prism Core (UML)

13. Prism Core (Cont) • Ports • Link made by welding 2 ports together • Port can be welded to another corresponding port • Associated Types • Request • Reply • Events placed on a port are forwarded to its linked port • Request events: forwarded from request to reply ports • Reply events: forwarded in opposite direction

14. Prism Core (Ports)

15. Prism Core (Components) • Component • Performs computations in an architecture and maintains its own state • Each component has an arbitrary number of attached ports • Interact with each other by exchanging events via ports • Interacts either directly through ports or via connectors

16. Prism Core (Connectors) • Connectors • Central routing of events • Has arbitrary number of attached ports • Component attaches to a connector by creating a link between one of its ports • Components/Connectors can remove and add ports at runtime

17. Prism Core (Interfaces) • Interface • Each subclass of brick has an associated interface • IComponent – send and handle methods • IArchitecture – weld method attaches 2 ports • IConnector – handle method for routing events • IPort – provides setMutualPort method for creating one-one association between 2 ports

18. Prism Semantics • Event processing performed through Shepherd thread • Shepherd thread removes the event from head of queue • If component generates further events, it is added to end of queue • Benefits • Event routing to multiple destinations reduces power consumption

19. PrismMW Design • Extensibility • Core constructs are subclassed via specialized classes • Each AbstractExtension class can have multiple implementations

20. Support for Prism Setting • Distribution • 5 different port extensions are implemented • DistributionEnabledPort • Operates in server mode (has listening thread) • Has arbitrary number of network connections • Broadcasts events on all network connections • One-to-many association between ports • Varies from the basic port (one-to-one) • Deposits events on the network instead of local event queue

21. Distribution Scenarios

22. Support for Prism Setting (cont.) • Communication Properties • Security • AbstractSecurity – port extension providing RSA and authentication services • Delivery Guarantees • AbstractDeliveryGuarantees • AbstractDeliveryGuaranteesEvt • Support event delivery guarantees • Real-Time Delivery • AbstractRealTimeEvt • Assigns a real time deadline to an event • Data Conversion and Compression • AbstractXMLConversion – Encoding/Decoding via ports • AbstractCompression – minimizes network bandwidth for event dispatching

23. Support for Prism Setting (cont.) • Awareness • ExtensibleComponent • Contains references to the architecture object via IArchitecture interface • Observes components at the metalevel to facilitate different aspects of execution of application-level components • Developer can add metalevel components to a running application

24. Support Prism Setting (cont.) • Deployment and Mobility • Configuration of components deployed onto a set of connected hosts • Stateless Mobility/Deployment • ExtensibleEvents – contains architectural elements • AdminComponent – contains a pointer to its architecture object, which allows runtime changes to its local subsystem’s architecture: • Addition, removal, connection, disconnection of components and connectors • Stateful Mobility • Provides the ability to transfer code between a set of hosts • Serialization-based technique – Forwarding of an element’s state • Disconnected Operation • Ability to continue functioning in the temporary absence of network connectivity

25. Architectural Style Support • Support provided by Prism: • Distinguish among different arch styles • Specify the arch. Elements’ stylistic behaviors • Specify rules and constraints • Use Multiple architectural styles within an application

26. Support for Individual/Multiple Styles • Individual Styles • Supported through an Extensible class • Simplified by using StyleFactory utility class • Example: Client and Server Style • Multiple Styles • Supported through hierarchical composition • ExtensibleArchitecture used to create components with their own internal archs.

27. Evaluation • Goals • Provide results of the performance trade-offs • Demonstrate the middleware’s efficiency and scalability in large distributed systems • Middleware Size • Basic Logic System • Memory Core: 2.3 KB • Connection Object: 8 KB • Port: 8.5 KB • TDS Architecture • 1 Headquarters, 4 commanders, 100 soldiers • Total memory overhead: 511 KB

28. Evaluation • Benchmark Results

29. Evaluation • Distributed Architecture Scenario • Only 2 percent in performance overhead compared to a “pure” java implementation

30. Group Work • Client and Server Style • Create a basic ClientServer representation using the below topology( refer to (d) of diagram): • One Server, Two Clients

31. Group Work • Use StyleFactory to match style for your Extensible [Architecture, Component] • StyleFactory methods below are static • Below is the format to follow(Java based): • Class ClientServer { static public void main(String argv[]) { //Create your architecture first (use ExtensibleArchitecture) //Each Extensible Component should have an implementation to describe it (3 in total, clients and server) //Add your components to the architecture (3 components to add) //Establish / Weld the connections between the clients -> server //Start the architecture architecture.start(); } }