HTTP: the Other ESB
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The document discusses the integration challenges within enterprise architectures, emphasizing the need for specialized tools for front and back office operations, while mentioning the issues related to application silos and changing schemas. It explores various messaging frameworks and protocols such as SOAP and REST, advocating for a shift towards a more semantic web approach utilizing hypermedia and stateless interactions. The conclusion highlights a paradigm shift from traditional architectures to a more evolved perspective in software engineering, with references to essential resources and frameworks for further reading.
HTTP: the Other ESB
- 1. HTTP: the other ESBRyan RileyCatapult Systems, Inc.Houston TechFest 2009
- 2. AgendaSetting the StageAlternativesHTTP: the application protocolCommon ConcernsQuestionsResources
- 4. First things firstDemand – Specialized ToolsDifferent tools needed among front and back office, as well as field workersOnce people get used to a tool, they don’t want to change … except to get the features they wantSupply – One-size-fits-allCreate reusable frameworks or components and force them to fit the needSave time and money (80/20 rule)
- 5. The result?Old Computer Equipment 1 from Dolor IpsumSome rights reserved
- 6. The Integration ProblemStart with Application SilosThen need to Share and Aggregate DataNote:Different systems with different needsDifferent interpretations of data semanticsMUST communicateSystems rarely die, but we keep adding more
- 7. The ContendersFile sharingDatabasesDirect sharing or ETL / Data StoresHow do you negotiate schema changes?Message-Oriented Middleware (MOM)Fire and forgetVendors rule the world: Message Broker, ESB, etc.Service-Oriented Architecture (SOA)Back to silosWhich platform: Java, .NET, ESB framework, etc.
- 8. Complexity becomes usStarts simpleEnds …Spaghetti? Yum! from DanoSome rights reserved
- 9. ESB to the rescue!
- 10. … or perhaps not“Enterprise Spaghetti Bus” – Jim Webber
- 11. Meanwhile …New patterns and practicesAgile and LeanTDD, BDD, DDD, CI, CQS/DDDD, etc.Frameworks and tools to the rescue!The web as an application platformWS-* emerges as an SOA solutionRails & co make web programming easier
- 12. Alternatives
- 13. WS-*Messaging: SOAPDiscoverability: WSDLSecurity: WS-SecurityReliability: WS-MessageReliabilityAnd a host of others:WS-BusinessActivityBPELEtc.
- 14. WS-* (cont.)ScalabilityReliance on HTTP POSTComplex to achieveTransactionsComplicated protocolsBased on classic RPC paradigmsBrought to you by HTTP POST
- 15. Other alternativesESB frameworks: NServiceBus, MassTransit, Rhino.ServiceBus, etc.Back to file/database sharing?Most of these are fire and forget models.
- 16. HTTP: the application protocol(and you thought the second T was for transport?)
- 17. HTTP is comprehensiveHTTP verbsGETPUTPOSTDELETEHEADOPTIONSAnd more through extensibility!
- 18. MessagingRequestResponseIt’s about communication!GET /index.html HTTP/1.1Accept: application/xhtml+xmlAccept-Language: enHTTP/1.1 200 OKContent-type: application/xhtml+xmlContent-length: 16Hello TechFest!
- 19. Status Codes100 – 101 Informational200 – 206 Success300 – 307 Redirection400 – 417 Client Error500 – 505 Server Error
- 20. GETIdempotent = massively scalable via cachingControl caching through HTTP headers:Client => Last-Modified + If-Modified-Since or If-None-Match + ETagServer => Cache-Control and Expires
- 21. PUTUseful for updating and creatingIdempotent = safe to repeat
- 22. POSTCreate a new resourceNot necessarily safe
- 23. DELETEDisable a resource (though not necessarily destroy)Safe to repeat, but the response is generally different when the resource doesn’t exist.
- 24. HEADRetrieves only the headersConditional GET
- 25. OPTIONSRetrieves the HTTP verbs a resource URI will accept.The protocol tells the client how it may proceed.
- 26. Hypermedia TypesXHTML (application/xhtml+xml)RSS (application/rss-2.0)Atom/AtomPub (application/atom+xml)Custom (application/vnd.my-format)
- 27. XHTML?
- 29. Why not XLink?Open XML link extensionNot well understood nor clearly definedIn the end, you would still need custom processing, so use application/vnd.custom+xml instead of application/xml
- 30. Atom / AtomPubWell-understood hypermedia formatCollection <atom:feed> and single <atom:entry> formatsCan use <atom:link> within custom media types for well understood link semanticsWorks well as a queue (if you must)Simple and extensibleDebate over message formats in REST
- 31. Add SemanticsMicroformatsRDF / RDFa(FOAF)Prefermicroformats(rel tag)
- 32. The Role of HypermediaREpresentational State Transfer (REST)Accept header(contentnegotiation)State transitions / Workflows (HATEOAS)Single entry pointNext steps provided through linksCan swap out providers (links)GET /index.html HTTP/1.1Accept: application/xhtml+xml, application/jsonAccept-Language: en
- 34. HATEOAS, cont.No HATEOASWith HATEOAShttp://www.infoq.com/articles/subbu-allamaraju-rest
- 35. ReliabilityIdempotencyResponse Error CodesHTTP is synchronous by natureOther ESB platforms are generally asynchronousFire and forgetNeed additional fault tolerance mechanisms
- 36. SecurityHTTP Basic and Digest authenticationHTTPs, the tried and true (but not cahceable)OpenID, OpenAuth, SAML
- 37. ScalabilityStateless, so massively scalableClient and Proxy caches
- 38. TransactionsHypermedia (HATEOAS)Different paradigm with richer semanticsWorkflows and state transitions
- 39. How to GET a Cup of Coffeehttp://www.infoq.com/articles/webber-rest-workflow
- 40. Common Concerns
- 41. Security ConcernsIsn’t the web inherently insecure?HTTPs is used everyday to transact millionsOther protocols emergingOpenId + OpenAuthSAML
- 42. ComplexityFew frameworks exist for pure HTTP useRESTClient and Sinatra (Ruby)Limonade (PHP)OpenRasta (.NET)Fairly simple to create from scratchMash-ups (just see how easy this is)On the webCall services from within Excel
- 43. OpenRasta (C#)
- 44. Limonade (PHP)
- 45. Sinatra (Ruby)
- 46. Tight-couplingThis is a fear from having used WSDLHATEOAS reduces coupling even more!Don’t use URI templates (except internally)URIs can be swapped at any timeRequires a layer in between your domain and the external APIUpgrade client and server independently (Accepts header)
- 47. Summary
- 48. There is no spoon (or bus)Paradigm shiftDumb network vs. Smart networkMeaningful semantics over classic, distributed spaghetti architectureTake advantage of theexisting, richinfrastructure
- 49. Distributed computing for years now has seemed like an endless repackaging of the same old ideas, patterns, and technology. Through REST, I finally feel like distributing computing is evolving and moving forward again. While REST won't solve world hunger, it will certainly give us a new perspective to practice software engineering.~ Bill Burke, JBoss
- 50. Questions?
- 51. ReferencesDr. Roy Fielding’s DissertationHTTP/1.1 (rfc2616)The Atom Syndication FormatThe Atom Publishing Protocol
- 52. BooksGet /Connected (coming 2009/2010)(Parastatidas, Robinson, Webber)RESTful Web Services(Richardson & Ruby)RESTful Web Services Cookbook(Allamaraju & Amundsen)
- 53. PresentationsGet /ConnectedGuerilla SOAA Couple of Ways to Skin an Internet Scale CatDoes My Bus Look Big in This?RESTful Approaches to Financial Systems Integration
Editor's Notes
- #7: The audit problem
- #8: Files – each party manages their own world, but changes break downstream clientsDatabases – both parties now have to agree on schema changes. What about data validation (business logic) across systems?MOM – How do you determine rate of processing? Front-office may want real-time; back-office often are okay with high latency.SOA – Some standards, but not all vendors use the same standards; publisher determines format and may take your needs into consideration. So you have “kind of” communication.
- #9: Planning systems upgradesDifferent platforms and dev toolsMost people just want their ExcelDifferent architectures, expectations, security, etc.Because you are forced to talk to different platforms, you wind up with spaghetti.
- #10: Originall, ESB was seen as the hero. Look at that beautifully clean network diagram!
- #11: But the ESB just hides the spaghetti.Auditing BizTalk was never easy because you still have to understand which systems talk to which, how they do so, etc.
- #28: What exactly is XHTML (or HTML)?Currently, it’s the new spaghetti code.Cool new features coming in HTML5, but most of that is making this worse.It’s a document serialization format.