Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 0 Lezione 3a - 20 ottobre 2009 Il materiale didattico usato in questo corso è stato mutuato da quello utilizzato da Paolo Veronesi per il corso di Griglie Computazionali per la Laurea Specialistica in Informatica tenuto nellanno accademico 2008/09 presso lUniversità degli Studi di Ferrara. Paolo Veronesi Università degli Studi di Bari – Corso di Laurea Specialistica in Informatica Tecnologia dei Servizi Grid e cloud computing A.A. 2009/2010 Giorgio Pietro Maggi

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 1 Outline The Grid (riassunto delle puntate precedenti) Service Oriented Architecture (SOA) Richiami di HTTP Richiami di XML XML Namespaces, XML Schema

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 2 The Grid Metaphor

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 3 1. Grid computing: characteristics (2/4) The three fundamental properties of Grid computing: 1. Large-scale coordinated management of resources belonging to different administrative domains (multi-domain vs single domain) Grid computing involves multiple management systems 2. Standard, open, multi-purpose protocols and interfaces that provide a range of services (standard vs proprietary) Grid computing supports heterogeneous user applications 3. Delivery of complex Quality of Service (QoS): Grid computing allows its constituent resources to be used in a coordinated fashion to deliver various types of QoS, such as response time, throughput, availability, reliability, security, etc.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 4 Elements of the Problem Resource sharing: sharing issues today are not adequately addressed by existing technologies. Complex requirements: run program X at site Y subject to community policy P, providing access to data at Z according to policy Q High performance: unique demands of advanced & high- performance systems Heterogeneous resources: computers, storage, sensors, networks, … Sharing always conditional: issues of trust, policy, negotiation, payment, … Coordinated problem solving It extends the simple client-server: distributed data analysis and computation

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 5 5 The three main capabilities of a Grid middleware Virtualization of users and resources Site ASite B Grid system Mapping virtual resources to physical resources Mapping virtual users to physical users

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 6 Layered Grid Architecture (by Analogy to the Internet Architecture) Application Fabric Controlling elements locally: Access to, & control of, resources Connectivity Talking to Grid elements: communication (Internet protocols) & security Resource Sharing single resources: negotiating access, controlling use Collective Coordinating multiple resources: ubiquitous infrastructure services, app-specific distributed services Internet Transport Application Link Internet Protocol Architecture Grid Architecture Internet Architecture

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 7 Who Defines Standard for Grid OGF: Open Grid Forum community of users, developers, and vendors leading the global standardization effort for Grid computing OASIS: Organization for the Advancement of Structured Information Standards not-for-profit consortium that drives the development, convergence and adoption of open standards for the global information society DMTF: Distributed Management Task Force industry organization leading the development, adoption and promotion of interoperable management standards and initiatives W3C: World Wide Web develops interoperable technologies (specifications, guidelines, software, and tools) to lead the Web to its full potential

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 8 OGSA Capabilities Security Cross-organizational users Trust nobody Authorized access only Security Cross-organizational users Trust nobody Authorized access only Information Services Registry Notification Logging/auditing Information Services Registry Notification Logging/auditing Execution Management Job description & submission Scheduling Resource provisioning Execution Management Job description & submission Scheduling Resource provisioning Data Services Common access facilities Efficient & reliable transport Replication services Data Services Common access facilities Efficient & reliable transport Replication services Self-Management Self-configuration Self-optimization Self-healing Self-Management Self-configuration Self-optimization Self-healing Resource Management Discovery Monitoring Control Resource Management Discovery Monitoring Control OGSA OGSA profiles Web services foundation

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 9 Service Oriented Architecture (SOA)

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 10 Before to enter the game… We introduce the concept maps A simple convention for brainstorming concepts during the development of software systems and/or architecture Concepts maps are a two dimensional format composed of concepts (objects) and associations (relationships). Associations may be named to provide clarity

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 11 Concept Maps A line between two concepts represents a relationship The arrow on a line indicates an asymmetrical relationship, where the concept to which the arrow points can be interpreted as depending in some way on the concept from which the line originates (Concept 1) Lines can have labels or descriptive text

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 12 Why we talk about concept maps? In general, they are used to identify concepts and relationships in a new investigation domain We use them to sketch the concepts related to the Service Oriented world by defining a Reference Model

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 13 What is SOA; what is a reference model for SOA Why is a reference model needed The OASIS SOA RM

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 14 Defining SOA Definition of Architecture: Architecture: A software architecture for a system is the structure or structures of the system, which consist of elements and their externally visible properties, and the relationships among them. If Service Oriented Architecture is Architecture, as the name implies, it should be definable as architecture. This should not be done by referencing specific implementations.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 15 Closer look: Service Oriented Is a paradigm (model) for software architecture. Focus herein is software & systems architecture Services are the central concept; other concepts are present. SOA not currently defined other than a common law or defacto perception of what it is. Perceptions for definition of SOA are vastly disparate.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 16 What is a SOA Reference Model? Is a model for developing a range of Service Oriented Architectures and analysis/comparison thereof. Is not architecture for a single implementation. This is very important to understand since things you may see in other architecture might not be present in the Reference Model. Is a framework for understanding significant relationships among the elements of a SOA environment. Is based on concepts present in all SOAs. A Reference Model defines SOA in an abstract sense. Example: Abstract = Service Description Concrete = WSDL

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 17 To develop a Reference Model for SOA Some questions: What elements are common in all implementations of SOA? (Paraphrased) What are the core things that make SOA service oriented? How do we describe those as abstract concepts? What relationships exist amongst those concepts? How do we represent those concepts without referencing concrete implementations.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 18 Draft Conceptual SOA Reference Model

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 19 Base Components Service: A behavior, or set of behaviors provided for use by another entity. Service Description: A specification of the information necessary to: allow a potential consumer to determine whether or not this service is applicable, and facilitate invocation. Advertisement: A methodology to convey awareness of (the existence of) a service(s) to all consumers on a fabric. Advertising makes discovery possible.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 20 Base Components and Concepts of SOA Data Model: The logical expression of a set of information items associated with the consumption of a service or services. Contract: The syntactic, semantic and logical constraints governing on the use of a service.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 21 SOA Axioms 1. A Service is a set of functionality provided by one entity for the use of others. 2. Services are conceptually autonomous (self sufficient) and opaque (independent of underlying technology) in nature. 3. There is no need to make architectural distinctions between services that are consumed as part of a process vs. ones that are not. 4. There is not always a one to one correlation between on the wire requests to invoke a service and service responses being consumed. 5. Each logical Service has exactly one canonical Service Description.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 22 SOA Axioms 6. A Service Description is comprised of three logical parts - Data Model - The logical expression of a set of information items associated with the consumption of a service or services; - Policy - Assertions and obligations that service consumers and/or providers must adhere to or provide; and - Contract (and/or offer thereof) - the syntactic, semantic and logical constraints governing on the use of a service. 7. A security policy is a specialized type of the Service Description policy noted above. 8. Service Policy may mandate security requirements to be met, and if they are not, interaction (with the service) may be refused.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 23 SOA Axioms 9. A null security policy is still logically considered a policy. 10. A Service Description is advertised to consumers on a fabric to make it discoverable. 11. Discovery does not constitute authorization to execute against the service.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 24 What is SOA; what is a reference model for SOA Why is a reference model needed The OASIS SOA RM TC

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 25 Existing situation WSDL XML & Schema SOAP Base Standards WS-RM WS Addressing Reg/Rep UDDI WS-Security WS-Trust WS-* Requirements Question: How do I account for my requirements and organize components when building a concrete architecture?

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 26 Thoughts on developing specific SOAs Probably not logical to try and develop a one size, fits all architecture for SOA or WS. Not rational to develop multiple architectures in standards bodies for every set of requirements. Best solution: develop an SOA reference Model. Used by architects to guide development of specific service oriented architectures. Model for a way of thinking when architecting. Re-useable by multiple architects writing SOA for multiple domains. Helps architects slot existing standards into their architectures.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 27 SOA RM used for range of architectures WSDL XML & Schema SOAP Base Standards WS-RM WS Addressing Reg/Rep UDDI WS-Security WS-Trust WS-* Requirements Guides developments of SOA-RM Specific Architectures Uses Input for

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 28 What is SOA; what is a reference model for SOA Why is a reference model needed The OASIS SOA RM TC

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 29 OASIS SOA Reference Model Chartered February 2005 Problem to be solved: "Service Oriented Architecture" (SOA) as a term is being used in an increasing number of contexts and specific technology implementations, sometimes with differing or conflicting understandings of implicit terminology and components. The proposal to establish a Reference Model is intended to encourage the continued growth of specific and different SOA implementations whilst preserving a common layer that can be shared and understood between those or future implementations.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 30 OASIS SOA Reference Model TC Purpose: The SOA-RM TC will deliver a Service Oriented Architecture Reference Model (SOA-RM). The TC may also create sub-committees, promotional material, liaisons or other promulgation of the TC's work, in order to promote the use of the SOA Reference Model. May help vertical industries develop SOA for their requirements.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 31 Definition Reference Model: A reference model is an abstract framework for understanding significant relationships among the entities of some environment, and for the development of consistent standards or specifications supporting that environment. A reference model is based on a small number of unifying concepts. A reference model is not directly tied to any standards, technologies or other concrete implementation details, but it does seek to provide a common semantics that can be used unambiguously across and between different implementations.

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 32 The OASIS SOA Reference Model Centered around the notions of needs and capabilities SOA provides a powerful framework for matching needs and capabilities and for combining capabilities to address those needs

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 33 Needs and Capabilities Entities (people and organizations) create capabilities to solve or support a solution for the problems they face in the course of their business Just as one persons needs may be met by capabilities offered by someone else There is not necessarily a one-to-one correlation between needs and capabilities The granularity of needs and capabilities are driven by the business, therefore they vary from fundamental to complex Any given need may require the combining of numerous capabilities, while any single capability may address more than one need

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 34 Five key questions to interact with a Service 1. How can the Consumer dynamically discover the existence of a Provider, which can provide the services being requested? 2. Assuming the Consumer knows of the Providers existence, how can it locate the Provider? 3. Assuming the Consumer has located the Provider, how can the two describe how to connect to each other, in a standard format which can be understood regardless of their IT platforms? 4. Assuming they have described themselves, how can they exchange messages in a common messaging format which is independent of their underlying platforms? 5. Assuming they have agreed upon a common messaging format, what data format can they use to exchange data independent of their underlying database technologies? Application 1 Service Consumer Application 2 Service Provider

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 35 What is Service Oriented Architecture (SOA)? An SOA application is a composition of services A service is the atomic unit of an SOA Services encapsulate a business process Service Providers Register themselves Service use involves: Find, Bind, Execute Most well-known instance is Web Services Service Registry Service Provider Service Consumer FindRegister Bind, Execute

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 36 SOA Actors Service Provider Provides a stateless, location transparent business service Service Registry Allows service consumers to locate service providers that meet required criteria Service Consumer Uses service providers to complete business processes Service Registry Service Provider Service Consumer FindRegister Bind, Execute

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 37 SOA Benefits Business Benefits Focus on Business Domain solutions Leverage Existing Infrastructure Agility Technical Benefits Loose Coupling Autonomous Service Location Transparency Late Binding Service Registry Service Provider Service Consumer FindRegister Bind, Execute

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 38 What is not in the Reference Model? Service composition Choreography, orchestration Process Oriented Architecture Organizational framework Who is doing what to whom Specific technologies not even specific architectures

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 39 The OASIS SOA reference model – Central concepts Service About services Service description Policies and Contracts Execution context Dynamics of Services Visibility Interacting with services Real World Effect

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 40 The OASIS SOA reference model – Central concepts Service About services Service description Policies and Contracts Execution context Dynamics of Services Visibility Interacting with services Real World Effect

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 41 Service A mechanism to enable access to one or more capabilities using a prescribed interface consistent with constraints and policies as specified by the service description A service is opaque in that its implementation is typically hidden from the service consumer except for the information and behavior models exposed through the service interface the information required by service consumers to determine whether a given service is appropriate for their needs

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 42 Visibility Visibility is the relationship between service participants that is satisfied when they are able to interact with each other Awareness Service description Discovery Willingness Policy & contract Reachability Communication

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 43 Service Description The service description represents the information needed in order to use, manage or provide a service Service reachability Service functionality Service policies Service interface

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 44 Anatomy of a Service Service Consumer Interface Proxy Service Interface New Service Wrapped Legacy Composite Service Transformation Layer Service Implementation

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 45 OO vs. SO Object OrientationService Orientation When typically used Use Within enterpriseBetween enterprises Program language dependencies Tied to a set of programming languages Program language independent CouplingTightly-coupledLoosely-coupled Communication paradigm ProceduralMessage-driven Communication protocol Usually bound to a particular transport Easily bound to different transports EfficiencyEfficient processing (space/time) Relatively not efficient processing

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 46 Why is it different? SOA reflects the reality of ownership boundaries CORBA, RMI, COM, DCOM, etc. all try to implement transparent distributed systems Ownership is of the essence in SOA SOA is task oriented Services are organized by function Getting something done SOA is inspired by human organizations It worked for us, it should work for machines

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 47 A Service-Oriented Grid Virtualized resources Grid middleware services Brokering Service Registry Service Data Service CPU Resource Printer Service Job-Submit Service Compute Service Notify Advertise Application Service

Tecnologia dei Servizi Grid e cloud computing - Lezione 003a 48 OGSA: focus on Web Services foundation Security Cross-organizational users Trust nobody Authorized access only Security Cross-organizational users Trust nobody Authorized access only Information Services Registry Notification Logging/auditing Information Services Registry Notification Logging/auditing Execution Management Job description & submission Scheduling Resource provisioning Execution Management Job description & submission Scheduling Resource provisioning Data Services Common access facilities Efficient & reliable transport Replication services Data Services Common access facilities Efficient & reliable transport Replication services Self-Management Self-configuration Self-optimization Self-healing Self-Management Self-configuration Self-optimization Self-healing Resource Management Discovery Monitoring Control Resource Management Discovery Monitoring Control OGSA OGSA profiles Web services foundation