SLA-Aware Enterprise Service Computing


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SLA-Aware Enterprise Service Computing

  1. 1. SLA-Aware Enterprise ServiceComputing Longji Tang, PhD in CSSE
  2. 2. Agenda Introducing Myself Challenges of Enterprise Service Computing SLA-Aware Enterprise Service Computing  SLA-Aware SOAP Web Service Architectural Style  Can REST Web Service be SLA-Aware? ConclusionSeptember 19, 2012 2
  3. 3. Introducing Myself  My name is Longji Tang, PhD in Software Engineering, I graduated from Computer Science of University of Texas Dallas, 2011.  My PhD dissertation title is “Modeling and Analyzing Enterprise Service-Oriented Architectural Styles”  Currently, I am a Sr. Technical Advisor in FedEx IT. I have been working in IT industry since 1995 as developer, architect, project manager of data center move project.September 19, 2012 3
  4. 4. Agenda Introducing Myself Challenges of Enterprise Service Computing SLA-Aware Enterprise Service Computing  SLA-Aware SOAP Web Service Architectural Style  Can REST Web Service be SLA-Aware? ConclusionSeptember 19, 2012 4
  5. 5. Challenges of Enterprise Service Computing amazon_server_outage/index.htm September 19, 2012 5
  6. 6. Challenges of Enterprise Cloud ServiceComputing 19, 2012 6
  7. 7. Challenges of Enterprise Service ComputingIn the Fig. we’ve displayedin order of fastest averageperformance across theglobe, the top rankedservice provider sites. Thisrepresentation only includesprovider sites we’ve beentesting for 6 months orlonger, eliminating dispersaland I hope… yielding themost honest display ofresponse times across thebest of the best. by CloudSleuth, 2011 19, 2012 7
  8. 8. Challenges of Enterprise Service Computing – Facing the FactsOutages: Security Threads: Latency: 04/21/2011 – Amazon  2010 – the  2010 - Cloudkick - one of East Data Center Anonymous group the many outfits that EC2 outage which successfully crashed offer a service for caused many web and overseeing the use of sites down strained the websites Amazon EC2 and other 08/07/2011 – Amazon of Visa and PayPal. so-called compute clouds Dublin Data Center  Dropbox could indeed - first noticed an Amazon Power outage see the contents of latency spike around Google Email files, putting users at Christmas time, and the outages risk of government problem has grown searches, rogue steadily over the past 08/17/2011 - few weeks. Microsoft Office365 Dropbox employees, outage which and even companies  Aberdeens report - impacted its CRM trying to bring mass application performance customers copyright-infringement could impact overall suits. corporate revenues by up to 9%. September 19, 2012 8
  9. 9. What are the risks moving to cloud? The figures are from dynaTrace presentation in 2011 Cloud Expo • Projects fail to deliver acceptable performance • Service consumers’ business is impactedSeptember 19, 2012 9
  10. 10. Agenda Introducing Myself Challenges of Enterprise Service Computing SLA-Aware Enterprise Service Computing  SLA-Aware SOAP Web Service Architectural SLA-Aware SOAP Web Service Style Style  Can REST Web Service be SLA-Aware? ConclusionSeptember 19, 2012 10
  11. 11. SLA-Aware Enterprise Service Computing What are SLA and SLA-Aware? Why SLA? SLA-Aware Enterprise Service Computing  SOAP-Based SLA-Aware ESC  REST-Based SLA-Aware ESCSeptember 19, 2012 11
  12. 12. SLA-Aware Enterprise Service Computing Service Level Agreement is a negotiable QoS contract between service consumer (SC) and service provider (SP) on the service guarantees for service consumers. The guarantees include the operations that need to be executed and the promised QoS that should be provided. Formally, we define SLA as SLA= SLA (SC, SP, C(QoS)), such as Amazon’s EC2 Service Level Agreement ( 19, 2012 12
  13. 13. SLA-Aware Enterprise Service Computing SLA-Awareness is a capacity and design principle to guarantee QoS provided by services. It uses dynamic SLA binding in a service computing system environment to achieve its goal. The capacity and quality of an SLA-Aware service computing system is controlled by dynamic SLAs and managed by dynamic SLM. such as SOA@SOI SLA-Aware Web Service InfrastructureSeptember 19, 2012 13
  14. 14. SLA-Aware Enterprise Service Computing Benefits of Adopting SLA and SLA- Awareness in Enterprise Service Computing  Service providers can delivery better services with higher quality, since SLA is the design constrain.  Service providers can gain higher reputation and increase ROI and reduce failure penalty.  Service consumers can get the service value from what they pay.  Service consumers can get guarantee (include service violation benefit) from SP.  Both SP and SC can get dynamic and real-time high-assurance service from SLA-Awareness.September 19, 2012 14
  15. 15. SLA-Aware Enterprise Service Computing Dynamic SLA vs. Static SLA Vertical SLA vs. Horizontal SLASeptember 19, 2012 15
  16. 16. SLA-Aware Enterprise Service Computing SLA-Aware QoS Taxonomy SLA-Aware QoS Class Performance Depedability Security Cost & Payment· Response time · Availability · Security · Cost· Latency · Accuracy · Trust · Penalty· Round trip time · Robustness · Reputation · Service credit· Scalability · Reliable message· Throughput · Error rate· Transaction rate· Connect time September 19, 2012 16
  17. 17. SLA-Aware SOAP Web Service Architectural Style Framework, Standard and Language  Web Service Level Agreement (WSLA) : a specification and reference implementation proposed by IBM.  WS-Agreement: a specification from the Open Grid Forum (OGF) which provides an agreement protocol between service consumers and service providers.  WS-Policy and WS-Policy Attachment: specifications of service qualities which are part of SLA developed by the World Wide Web Consortium (W3C).  SLAng: an XML language for defining SLA which is a part of the contracts between web service clients and web services.  Web Service Offering Language (WSOL): a formal XML language compatible with the Web Services Description Language (WSDL).September 19, 2012 17
  18. 18. SLA-Aware SOAP Web Service Architectural Style SLA-Aware Architectural Style  SLA-Aware Web Services  SLA-Aware Web Service Consumers  SLA-Aware SOA Data  SLA-Aware SOA Infrastructure  SLA-Aware SOA Management  SLA-Aware SOA Process  SLA-Aware Quality AttributesSeptember 19, 2012 18
  19. 19. SLA-Aware SOAP Web Service Architectural Style Service Discovery SLA Dashboard Find Service Register registry Workstation Customer SLA-Aware Service Consumer SLA-Aware Service Provider Negotiating Client-Side SLA Management Offering Service Level Management or Service Level Mamagement Gathering Gathering Request service Claim QoS Provisioning SLA monitoring data data Service Delivery Cluster SLA-Aware Business Application invocating SLA-Aware Web Service or SLA-Aware Web service SLA Monitoring Monitoring Data Monitoring Agents serversSeptember 19, 2012 19
  20. 20. SOAP-Based We Service SLA-Aware ESC Cloud Cloud Workstation Laptops On-demand SLA-Aware Dynamic Data Center requests Enterprise Services Delivery Network Business Applications Delivery Network invoke Public Cloud Private Cloud Other Serices Services Services Business Applications ne Virtualized Infrastructure Provisioning Services ot g SOA Management ia te ri n g Service SLA Provisioning Service Policy nito monitoring Orchestration provision SLA Other mo Services Virtualization Management Managements Utility Handler Controller o rt ch g at re p ri n w ito Dynamic Virtualized Infrastructure Monitoring on m Virtual Virtual Virtual Servers Storages Network monitoring g itorin mo n Physical Resources Physical Resource ManagementSeptember 19, 2012 20
  21. 21. SLA-Aware SOAP Web Service Architectural Style Enterprise Application (travel reservation, call center, ….) SLA SLMi SLAi Monitoring Service Consumer Interface Service Provider Interface Enterprsie Services (search, ticket negotiation, billing, …) SLA SLMj SLAj Monitoring Internal Service Delivery Network Service (IP, Ethernet, SAN) SLA SLMk SLAk Monitoring External Service Delivery Network Service (ATM, SDH, Dark Fiber)September 19, 2012 21
  22. 22. SLA-Aware SOAP Web Service Architectural Style SLA-Aware Travel SLA-Aware Reservation Client workflow SLA01 SLA2,IaaS1 s1 SLA12 Workstation Cloud Book airline s2 service IaaS1 · S1 is a travel booking service · S2 is a airline booking service s3 · S3 is a rental car booking service · S4 is a data service SLA13 SLA3,IaaS2 s4 BPEL Cloud Book car Engine service IaaS2 SLA4,IaaS3 Storage Infrastructure DataSeptember 19, 2012 22
  23. 23. Agenda Introducing Myself Challenges of Enterprise Service Computing SLA-Aware Enterprise Service Computing  SLA-Aware SOAP Web Service Architectural Style  Can REST Web Service be SLA-Aware? Can REST ConclusionSeptember 19, 2012 23
  24. 24. Can REST Web Service be SLA-Aware?REST-WS SOAP-WS Unified interfaces  Flexible interfaces with POST GET/PUT/POST/DELETE  Transport agnostic Mostly HTTP Transport  Comparatively higher Lightly bandwidth bandwidth QoS support – based on  Wide array of message level transport QoS options – WS-* Complexity - lower  Complexity - higher Communication Overhead –  Communication Overhead – high higher Response is cacheable by  Not cacheable, you have to client, server or proxy use server-side cache tech Suited for lightweight scenario  Suited for heavyweight scenarioSeptember 19, 2012 24
  25. 25. Can REST Web Service be SLA-Aware? Dynamic SLA or SLA-Aware depends on many Technologies:  Standards, Languages and Tools  Machine Readable Service QoS Description  Service Monitoring  Service Level Management (SLM) SOAP-WS is comparatively mature and more supported in all technologies above. REST-WS lacks all mature technologies above and is less supported as well as immature in them. Adding complicated dynamic SLA or SLA-Aware system to REST-WS architecture is not necessary, since it will violate the simplicity of REST-WS. However finding a lightweight way to do dynamic SLA for REST-WS is critical for enterprises. September 19, 2012 25
  26. 26. Standards, Languages and Tools WDSL 2.0 – Recommended by W3C, 2007  Provided formal way to describe REST Web Service  Potentially to define QoS – features and properties  Could not describe “content negotiation” – not SLA-Aware WADL (Web Application Description Language) – W3C Member Submission, 2009  a XML-based description language for HTTP-based Web applications, such as applications which follow the REST architectural style  WADL is not yet widely supported. It has the advantage over the more complicated WSDL in that it does not impose any further level of abstraction on the service description; however, as tools become available for application development with WADL, it is likely they will include ways of automatically generating WADL, and this risks imposing an RPC style on it, going against the intended simplicity of REST.  Google REST API Compile and Google REST Describer based on WADL, 2007 by Thomas SteinerSeptember 19, 2012 26
  27. 27. Context, Quality and Relevance of REST-WS Context – conditions for the service usage Quality – QoS (response time, availability, ….) Relevance of service outcome – a service outcome (representation) is considered relevant when the provided results match the service consumer (customer)’s need. Specifying context and quality in JSON Describing context and quality in WADL “Context, Quality and Relevance: Dependencies and Impacts on RESTful Web Services Design”, by Hong-Linh Truong, et al.September 19, 2012 27
  28. 28. Context, Quality and Relevance of REST-WS QoS in JSONQoS in WADL “Context, Quality and Relevance: Dependencies and Impacts on RESTful Web Services Design”, by Hong-Linh Truong, et al.September 19, 2012 28
  29. 29. Monitoring Technology for REST-WS SLA Metrics of SALMon Architecture of SALMon SALMon: A SOA System for Monitoring Service Level Agreements, by Marc Oriol, Xavier Franch, Jordi MarcoSeptember 19, 2012 29
  30. 30. Monitoring Technology for REST-WS SLAAmazon CloudWatch Developer Guide RightScale Dynamic Monitoring TechnologySeptember 19, 2012 30
  31. 31. Content Negotiation of REST-WS The service consumer and service provider of WS-* style web services can negotiate QoS or SLA through WS-Agreement. The question is if REST service consumer and REST services can negotiate QoS. Roy Fielding presented “Content Negotiation” of REST in his PhD thesis. “If the value set of a resource at a given time consists of multiple representations, content negotiation may be used to select the best representation for inclusion in a given message.” I think Content negotiation can be regarded as one of dynamic SLA for REST-WS. Content negotiation is a mechanism defined in the HTTP specification that makes it possible to serve different versions of a document (or more generally, a resource representation) at the same URI, so that user agents can specify which version fit their capabilities the best. (sort of QoS) In the new book “SOA with REST, the “Content Negotiation” is defined as a REST design patternSeptember 19, 2012 31
  32. 32. Content Negotiation of REST-WS Content negotiation is one of the core concepts of RESTful systems where a client can indicate which media type(s) it prefers. Also within the media types it can specify the order of preference. Client does this by using Accept header. For example, consider the following Accept header – (negotiated by content types) Accept: application/xml;q=0.8, application/json;q=0.9 It indicates to the server a) it can accept XML and JSON formats and b) it prefers JSON over XML (by providing higher value for q parameter. q value ranges from 0.0 to 1.0, higher value indicates more preference). Another more complex example:September 19, 2012 32
  33. 33. From WS-Agreement to REST-Agreement WS-Agreement describes an XML schema for specifying service level agreement (SLA) and a simple protocol that describes how parties can communicate to build an agreement among them. WS-Agreement (Open Grid Forum or OGF) is one of tech standards for building dynamic SLA or SLA-Awareness in SOAP-WS systems. Roland Kubert, et al, proposed a REST-Agreement:  Identifying resources – Template, list of templates, agreement, list of agreements, agreement state  Describing on resource representations by XML  Defining URIs:  /rest-agreement/templates (GET)  /rest-agreement/templates /search{query} (GET)  /rest-agreement/template/{id} (GET)  /rest-agreement/agreements (POST)  /rest-agreement/agreement/{id} (GET)  /rest-agreement/agreement/{id}/state (GET)  Validating templates, offers and agreements – to ensure the correctness of an SLA instance, the validation includes:  Every SLA instance is in XML format.  Every SLA template or SLA is an instance of the REST-Agreement XSD.  Handling state  Encode state in URIs or  Store state in a persistent storage and encode a reference to the state in the URIs.September 19, 2012 33
  34. 34. Does the REST-Agreement violated REST constraint? “We next add a constraint to the client-server interaction: communication must be stateless in nature, as in the client- stateless-server (CSS) style of Section 3.4.3 (Figure 5-3), such that each request from client to server must contain all of the information necessary to understand the request, and cannot take advantage of any stored context on the server. Session state is therefore kept entirely on the client.” “This constraint induces the properties of visibility, reliability, and scalability.” -- Chapter 5 of Roy Fielding PhD Thesis REST-Agreement Proposed by Roland needs to keep agreement state on the server-side. It slightly violates REST “stateless” constraint. To satisfy some of enterprise requirements or needs from cloud computing, such as dynamic SLA management, negotiation feature between service consumers and service providers, I do think we need to relaxing some of REST constraints. It is a design tradeoff. You sacrifice certain scalability, but you get REST SLA feature.September 19, 2012 The University of Texas at Dallas 34
  35. 35. Agenda Introducing Myself Challenges of Enterprise Service Computing SLA-Aware Enterprise Service Computing  SLA-Aware SOAP Web Service Architectural Style  Can REST Web Service be SLA-Aware? ConclusionSeptember 19, 2012 35
  36. 36. Conclusion Introduced SLA-Aware Enterprise Service Computing Presented SLA-Aware SOAP-WS Architectural Style Discussed Potential Approach of Dynamic SLA for REST-WS Finding lightweight way to make RESTful web service QoS-Aware & SLA-Aware is important to enterprise service computing.September 19, 2012 36
  37. 37. References Longji Tang, Modeling and Analyzing Enterprise Service-Oriented Architectural Styles, PhD Thesis, UTD, 2011 Roy Fielding, Architectural Styles and the Design of Network-based Software Architectures, PhD Thesis, University of California, Irvine, 2000. Raj Balasubramanian, Benjamin Carlyle , Thomas Erl , Cesare Pautasso,Herbjörn Wilhelmsen and David Booth, SOA with REST: Principles, Patterns & Constraints for Building RESTful Enterprise Solutions, Prentice Hall, 2012.September 19, 2012 37
  38. 38. Thank You!September 19, 2012 38