Web Services and Service Oriented Architecture

CS 4720 – Web & Mobile Systems

CS 4720 The tradional soware model • Organizaons build it all from scratch – “We can't trust anyone! Our competors will sabotage us!” – “We must own everything! Hardware and soware!” • Companies that build soware need components that do X or Y… – … so they buy COTS components – Service contracts, new releases, regression tesng…

2 CS 4720 The tradional soware model • How well does this work? • Some project data from the DOD: – 47% of soware delivered could not be used • Usually didn't meet requirements – 29% of funded soware never delivered • Usually canceled due to cost/schedule overruns – 19% of soware useful aer extensive rework • Costs 36 mes more to ﬁx problems aer release

3 CS 4720 A push to distribuon • “We're really good at ______, how can we get our ______out for people to use?” • The idea of distributed compung – “We're good at X, but not so good a Y…” – “What if we got someone to help us with Y… but in a way that we didn’t have to include any fancy libraries… – … and we could use them in web apps! And mobile devices! And even desktop apps!”

4 CS 4720 A Web Service • From W3C: “a soware system designed to support interoperable machine-to-machine interacon over a network. It has an interface described in a machine-processable format (speciﬁcally WSDL). Other systems interact with the Web service in a manner prescribed by its descripon using SOAP-messages, typically conveyed using HTTP with an XML serializaon in conjuncon with other Web- related standards”

5 CS 4720 A Web Service? • Huh? • A bit more simply: A program, accessible via the Internet, that can do some funcon (either for free or a fee) and can be dynamically discovered and used. • So… I use web apps all the me… are those web services?

6 CS 4720 Web Service as RPC • The earliest form of a true “web services” was an RPC – remote procedure call. • Exactly what it sounds like – there is an exposed funcon/method that is accessed via the web where you pass the parameters and the method name and you get back a return value. • Noce how this is very diﬀerent from the RESTful model (verbs vs. nouns)

7 CS 4720 Web Service as SOA • RPC was okay… but it turned out to be a bit more language speciﬁc than we'd like • What if we just a structured message (like an XML document) that described what we wanted, as opposed to knowing the exact funcon call? • This is the basis of the Service-Oriented Architecture

8 CS 4720 Word By Word • What is a service? • "A service is a discoverable resource that executes a repeatable task, and is described by an externalized service specificaon.” • Business alignment – business requirements • Specificaons – self-contained, well specified • Reusability – general enough to be reused • Agreements – based on funcon, not plaorm • Hosng and discoverability – available • Aggregaon – can be combined to make bigger services

9 CS 4720 Word By Word • What is an architecture? • "A formal descripon of a system, or a detailed plan of the system at component level to guide its implementaon.” • “The structure of components, their interrelaonships, and the principles and guidelines governing their design and evoluon over me."

10 CS 4720 Architecture • Architecture is: – A high-enough level of abstracon that the system can be viewed as a whole and yet sll provides enough informaon to make decisions. – Supports the funconality of the system. – All implementaon details are hidden. • Service orientaon is a way of integrang a business as a set of linked services.

11 CS 4720 What are we actually trying to do?

Fork Receive PO

Update Customer Profile Get Items from Inventory

Branch Compute Subtotal

Compute Export Tax [ship within US] [ship outside US]

Compute Shipping Cost

Merge Compute International Shipping

Compute Total

Ship Order Join

12 CS 4720 OSI Model

13 CS 4720 OSI Model

14 CS 4720 The Stack

15 CS 4720 The Stack

ebXML UDDI Registries Discovery ebXML Contracts and CPA agreements OWL-S Service Process and workflow BPEL4WS BPML Model orchestrations WS-AtomicTransaction and WS- BTP QoS: Transactions BusinessXALcAtiNviGty WS-Reliable OWL-WS SSCeLrvice WS-Coordination QoS: Choreography Messaging ebXML Profile WSCI BPSS OWL-S Service WS-Security WSCL QoS: Conversations Grounding ebXML WS-Policy WSDL QoS: Service OWL PSL CPP descriptions and bindings ebXML RDF SOAP messaging Messaging XML, DTD, and XML Schema Encoding HTTP, FTP, SMTP, SIP, etc. Transport

16 CS 4720 The Stack

17 CS 4720 SOA – The Quick Version • Right now, you probably think of a soware system as being a collecon of classes / objects • But users don't think of systems like that… they think of systems as sets of funconality that help them do something • So… why do we use objects? – Easier to model – Easier to program – Easier to explain to other programmers

18 CS 4720 Or is it actually easier? • Turn our idea of a system 90 degrees • Funconality objects (procedural abstracon) is the key idea, not world objects (data abstracon) • This is the key in SOA – An SOA system has the funconalies as the main players, not the objects themselves – But more so, these services are provided by many diﬀerent players

19 CS 4720 But what language do we speak? • SOAP - Simple Object Access Protocol – A communicaon protocol – A format for sending messages – Plaorm independent – XML based – Follows the rules that allow for transmission easily over HTTP, SMTP, etc. • Not really much more than an HTTP request that follows XML/SOAP standards

20 CS 4720 SOAP Model

21 CS 4720 SOAP Model

22 CS 4720 SOAP Request

POST /InStock HTTP/1.1 Host: www.example.org Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn

IBM

23 CS 4720 SOAP Response

• HTTP/1.1 200 OK Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn

34.5

24 CS 4720 Parts of SOAP • The Envelope – required root element deﬁning the document as being a SOAP request • The Header – not required, but contains authencaon and/or payment info for the request • The Body – the actual message being sent

25 CS 4720 But I like to be dirty! • …. • Bad tle aside, some didn't like to be “ed down” by such “conservave talk” of having to follow the SOAP rules! • “It's just XML!” they said. “I don't need of this extra stuﬀ! Just good Plain Old XML…!” • “And that's what we'll call it! POX!”

26 CS 4720 What's the diﬀerence? • Following the agreed upon rules… • Validang POX can be hard; SOAP is comparably easy • SOAP services are beer at being dynamically bound • How we do this is Thursday's lecture

27 CS 4720 Aer all this… What about REST? • REST is an architectural style that is independent, but compable, with XML • POX/HTTP means exchanging plain old XML documents over HTTP; can be RESTful • SOAP is a standard document format for building high-level protocols. Anything that uses SOAP is (by deﬁnion) not just using plain old XML, and thus not POX; it can also be RESTful

28 CS 4720 So… • So there can be RESTful SOAP applicaons, and RESTful POX applicaons, and non-RESTful SOAP applicaons, and non-RESTful POX applicaons, but no POX/SOAP combinaon… sort of

29 CS 4720 Thoughts • If you want a great experience for .NET/Java devs, you'll typically publish schemas and support SOAP. • If you want a great experience for LAMP folks, you'll support POX messages (or JSON) and will provide a non-XSD descripon of your formats. • If you want to reach both audiences, you'll do both #1 and #2. • If you want to reach both audiences before your compeon does, you'll avoid indulging in religious debates and ship something.

30 CS 4720 Using a Web Service • If you took the me to create a service, then you probably want people to use it • In order to use a service, users need to know what informaon they can send the service and what informaon is going to be sent back • What would be even beer is if the soware could do all this automacally…

31 CS 4720 Enter WSDL • WSDL: Web Services Descripon Language – An XML document used to give the speciﬁcs of a service • Locaon • Methods • Allowed messages • Potenal error messages

32 CS 4720 Enter WSDL

33 CS 4720 The HelloService Example • hp://oreilly.com/catalog/webservess/ chapter/ch06.html

34 CS 4720 Quick Sidestep: UDDI • UDDI: Universal Descripon, Discovery and Integraon • A soluon in search of a problem • The idea is okay: a language and schema for allowing people to publish their WSDL schemas so that others can discover their services • IBM, Microso, and SAP announced they were closing their public UDDI nodes in January 2006 • No one used it!

35 CS 4720 Quick Sidestep: UDDI • Where might it work decently? – Perhaps inside a single organizaon for internal code • The public sides were either: – Empty – Overrun with junk • Whichever it was UDDI, isn't really used • Quote Marty Humphrey: “It was a good problem to solve, but a terrible soluon.”

36 CS 4720 The Original Idea

37 CS 4720 Back to WSDL • We DO use WSDL though • It is how a web service is bound to an applicaon • It's more XML… which kinda sucks… • But… the best part is…

38 CS 4720 The Best Part about WSDL • No one ever writes the stuﬀ themselves! • It's auto-generated!

39 CS 4720 BPEL • Business Process Execuon Language – Standard executable language for specifying interacons with Web Services • Basic goal: an “execuon language” to write “systems” by tying available web services together

40 CS 4720 The Basic Idea

41 CS 4720 Video • hp://www.youtube.com/watch?v=XRzTySj- aak

42 CS 4720 Okay… so… • In a SOA… – Every funcon is a service – Every service is independent – Each service can talk to other services through a specified protocol (SOAP) – Each service defines what messages it can deal with through a specified protocol (WSDL) – Services can announce themselves to everyone else (UDDI or some other publishing scheme) – And services can be bundled into processes (BPEL)

43 CS 4720 That was exhausng… • Oh, it gets beer. Look at all the QoS stuﬀ…

44 CS 4720 What could possibly go wrong? • QoS: Quality of Service – Availability (MTTR): is it up? – Accessibility: if it's up, can I get to it? – Conformance to Standards: play by the rules? – Integrity: actually does what the WSDL says? – Performance: how fast does it come back? – Reliability: how does it handle failures? – Scalability: how does it handle lots of requests? – Security: what about all my data ﬂying around? – Transacons: if one part fails, does it all fail?

45 CS 4720 Bring in the lawyers • Service Level Agreements – Web services can come with contracts between the provider and the consumer that specify the requirements of the previous slide – Basically will boil down to how it will handle: • Performance and capacity • Availability • Security/Privacy • There are protocols for this too!

46 CS 4720 BAH! Is it worth it? • Verizon thinks so: • Rebuilt fraud detecon system into BPEL from J2EE • Used Oracle's BPEL Process Manager system • Original system: – Three large DBs consisng of 2.5 billion records – Team of 100

47 CS 4720 BPEL-ariﬁc • Tossed all the Java • Now it's one Shockwave (Flash) and one JSP page on top of the BPEL • Flash makes web services calls into the BPEL processes • All business rules wrien into the BPEL language • Web 2.0 UI

48 CS 4720 BPEL-ariﬁc • New code base is 0.5% of original size • 192 processor cores down to a single 8-core server • Energy consumpon down 99% • 20 terabytes of DB to 64 gigabytes

49 CS 4720 According to Verizon

• Based on event-driven architecture, data on cell phone usage coming from the Verizon switches is analyzed and checked for business excepons, Chappell explains. He site examples of possible fraud including business excepons such as the detecon of excessive data thresholds. This might indicate that someone is doing "phone cloning" to make calls by stealing a customer's account informaon. When this sort of excepon is detected, an event starts a BPEL process. • With the SOA implementaon, Chappell explains "the BPEL process invokes a number of services, which includes going out directly to the source of the call detail records to get the informaon necessary to enrich the event data. It is then fed into a rules engine to check for violaons, make decisions based on policy, and then on to generate more detailed reports." • Using this services approach rather than data warehousing to retrieve and process the required informaon reduces the storage requirements.

50 CS 4720 Thanks • Many thanks to Ken Anderson @ Colorodo for some of this informaon • Some info also from the ﬁne folks at Wikipedia • hp://www.pluralsight.com/community/blogs/ dbox/archive/2006/02/17/18869.aspx • This slide deck brought to you by the leer “∫” and the number “awesome.”

51 CS 4720