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Messaging with Web Services Enhancements 2.0

Messaging with Web Services Enhancements 2.0. Benjamin Mitchell Independent Consultant Microsoft Regional Director – UK Blog http://benjaminm.net/ benjaminm@benjaminm.net. What We Will Cover:. Overview of Web Services Enhancements 2.0 What problems does Messaging solve?

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Messaging with Web Services Enhancements 2.0

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  1. Messaging with Web Services Enhancements 2.0 Benjamin Mitchell Independent Consultant Microsoft Regional Director – UK Blog http://benjaminm.net/ benjaminm@benjaminm.net

  2. What We Will Cover: • Overview of Web Services Enhancements 2.0 • What problems does Messaging solve? • Why does Messaging solve them? • What types of Messaging models are there? • How can I use these programming models today?

  3. Web Services Enhancements • WSE implements many WS-* specifications • Simple, low-level object model for developers • Available for free download • Logically part of the .NET Framework, but kept separate while still evolving • Fully supported by Microsoft until at least 2008 • Version 1.0 Dec 2002, Version 2.0 May 2004 • Version 2.0 SP 2 pre-release available now • Benefits • Allows MS to gather real world feedback • Allows early adopters to use the latest standards

  4. WSE 2.0 • Designed to bring advanced Web Services technologies based on standard protocols to developers • Integrates with Visual Studio .NET and .NET Framework • What do you get with WSE? • WS-Addressing • WS-Security • WS-Policy • WS-SecurityPolicy • WS-Trust • WS-SecureConversation • WS-Referral • WS-Attachments • Interoperability

  5. How does WSE work? User Code SoapContext Policy Trace Referral Custom Security Security Token Manager Custom Filters

  6. Problem Statement • Issues with connected systems • Bandwidth and Latency • Domain boundaries • Coordination and Management • Solution • Less transparency • More Explicitness • Implementation • Message-based programming models

  7. Transparency • Transparent programming models are easy • But, they obscure: • Location of code execution • Complete context of execution • You don’t know that you don’t know

  8. Explicitness • Explicit programming models leave more for the developer to do • They do not obscure as much: • Network activity is apparent • Context and timing is known • You know you don’t know so you take precautions • Enables communication to offline services

  9. About Messaging • Several programming models within the "messaging" bucket • Eventing (often called Pub/Sub) • Dialogs • Queues • Request-Response • Key benefits • More natural fit for many business processes • Allows for more asynchronous processing • Many configurations • "Smart" routers • Offline machines • Etc…

  10. Web Services and Messaging • A way of exposing functionality using a set of interoperable protocols • Messages exchanged based on a shared schema • Independent of the programming language used • No shared classes • Unless you intentionally share them

  11. Messaging Implementations • MSMQ • Classic • Offline Queuing • ASMX • Easy to use • WSE V2 • Transport Independence • Host anywhere

  12. MSMQ Messaging • The classic messaging API • MessageQueue class • Two important methods • Send • Receive • Can provide reliable, in order, only once delivery as well as transaction support • Requires MSMQ at both ends of the pipeline

  13. ASMX Messaging • Easiest way to message with SOAP • Create an *.asmx file • Write a class • Decorate methods with [WebMethod] • OneWay or RequestResponse

  14. WSE 2.0 Messaging • WSE 2.0 includes a SOAP-based messaging API • Transport independence • Intra-AppDomain • For testing • Raw TCP • HTTP • Host Independence • Windows application • ASP.NET • Windows Service

  15. WSE 2.0 Messaging • SoapSender and SoapReceiver • One way messages • Deal with the SoapEnvelope rather than method parameters • Must implement method dispatching based on SoapEnvelope.Context.Adressing.Action • No automated reply messages • The Receiver must implement a new Sender • Sender must indicate reply address

  16. Demonstration 1 SoapSender and SoapReceiver

  17. WSE 2.0 Messaging (Continued) • SoapClient and SoapService • One-way and two-way • Uses SoapSender/SoapReceiver • Offers XML Serialization support • Operation-based dispatching • The Action is used to deliver the message to a Method • Automatic replying

  18. Demonstration 2 SoapClient and SoapServer

  19. WSE 2.0 Messaging (Continued) • Channels • Queued model • Raw, explicit programming

  20. Receiving Polling Push Adaptation Adapter Mapper Programming Models • Errors • Dead letter channel • Faults • Gateway • Aggregating Gateway • Router

  21. Programming Models: Receiving • Push-model CLIENT Implicit message receive Message is processed when message arrives Allows for Activation

  22. Demonstration 3 Push-model messaging with ASMX

  23. Programming Models: Receiving • Polling to receive messages CLIENT Explicit message receive Lets recipient control when message is processed

  24. Demonstration 4 Message Polling with WSE 2.0

  25. Programming Models: Adaptation • Application not always messaging aware • Too costly to re-code entire app • Adapters translate app-specific data and behavior into Messages ADAPTER APPLICATION

  26. Programming Models: Adaptation • Message on wire is serialized into common format • Message data on system not always serializable • Message mapper deals with this MAPPER MESSAGE DATA

  27. Programming Models - Errors • Two errors messaging is well-suited to deal with • Dead letters • Invalid messages • Exceptions • Exceptions can occur before dispatch • In user code • Soap Faults map to Exceptions • Fault codes are QNames

  28. APP CODE GATEWAY Design: Gateway • Wraps application-specific logic • Most Web services are gateways

  29. APP CODE GATEWAY Design: Gateway • Aggregator is gateway that combines several messages into one internal action

  30. Design: Router • Routes a message from a source to a destination SOURCE ROUTER DESTINATION

  31. Design: Router • Several type of routers • Splitters ROUTER • Aggregators ROUTER • Filters ABC ROUTER ABZ

  32. ABC ROUTER =DEF A =ABC B Design: Router • And content-based routers

  33. Design: Pub/Sub • Publication and Subscription • Message pattern • One message to subscribe • One to many messages publishing event information • Observer pattern over a distributed system

  34. Design: Pub/Sub • More on pub/sub SUBSCRIBE EVENT SERVICE SUBSCRIBER EVENTS

  35. Design: Pub/Sub • Two models for getting event data • Push – notification includes data • Pull – subscriber sends a request for the subscription data after receiving the event • Push is usually best for Web services • Pull is good when subscribers may not be interested in the data and the data is large or processor intensive

  36. Demonstration 5 Eventing

  37. Design: Reliability • Strongest and most resilient systems implement reliable messaging • Reliable messaging requires: • Idempotent processing • Durable storage NODE NODE

  38. Design: Dialogs and Queues • Dialogs are virtual connections between two nodes • With the help of queues, dialogs can be reliable and persistent across system resets

  39. Design: Dialogs and Queues • More on dialogs and queues NODE NODE

  40. Design: Long-Running Operations • Long-running operations • A key gain of messaging • Allows closer modeling of real-life business scenarios • Examples • User interaction is needed • Batch processing across multiple nodes

  41. Design: Long-Running Operations • Example NODE NODE NODE NODE NODE

  42. Design Guidelines • Avoid RPC and CRUD designs • Tends to encourage RPC like behavior • Interface may imply stateful interactions like enumeration • Interface is likely to be overly chatty • Don’t be too loose or extensible • Focus on encapsulating business processes • Use contracts to reduce coupling

  43. Session Summary • Messaging allows for apps that more closely match business processes • Applications that use messaging are more closely matched with business processes • Existing technology can be used to support messaging • WSE 2.0 provides extensible messaging with web services across multiple protocols

  44. Call to Action • Start designing with messaging in mind • Download WSE 2.0 Service Pack 1 • Download the Hands-On Labs on WSE Messaging from Aaron Skonnard • http://msdn.microsoft.com/webservices/building/wse/default.aspx

  45. For More Information • Blogs • http://benjaminm.net • Rebecca Dias WSE Product Managerhttp://weblogs.asp.net/rdias • Hervey Wilson Lead Developer WSE http://dynamic-cast.com • Newsgroup • microsoft.public.dotnet.framework.webservices.enhancements • Books • Enterprise Integration Patterns – Gregor Hohpe and Bobby Woolf

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