Asynchronous Messaging @DNUG Cologne, 07.04.2009
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The document discusses asynchronous messaging and its advantages over traditional RPC, highlighting benefits like loose coupling and separation of concerns. It outlines communication styles, the challenges of dependency tracing and debugging, and emphasizes messaging as the default approach for cloud-based services. The text also includes references for further guidance on messaging frameworks and service-oriented architecture principles.
Asynchronous Messaging @DNUG Cologne, 07.04.2009
- 1. Asynchronous Messaging Sergey Shishkin http:// shishkin.org Image source: http://www.flickr.com/photos/joits/1110215271/
- 2. Agenda Why Messaging? – And what’s wrong with good old RPC? Sample scenario – News module of the Prism’s StockTrader RI Under the hood of Message Bus – Building a Message Bus in 37 lines of code – And what those 37 lines did not cover? Image source: http://www.flickr.com/photos/mychatham/206928250/
- 3. Communication Styles Remote Procedure Calls Synchronous High coupling One-Way Messages Asynchronous Loose coupling
- 4. Fallacies of Distributed Computing* * http:// en.wikipedia.org/wiki/Fallacies_of_Distributed_Computing The network is reliable Latency is zero Bandwidth is infinite The network is secure Topology doesn't change There is one administrator Transport cost is zero The network is homogeneous Image source: http://www.flickr.com/photos/pascalcharest/308357541/
- 5. Composite Applications Image source: http://www.flickr.com/photos/curiouslee/2136283589/ Modularized applications are similar to distributed ones GUI composition is solved by: Common region infrastructure Event-based GUI synchronization Same pattern in broader context Common Message Bus infrastructure Message-based components integration
- 6. Tenets of Service-Orientation* Image source: http://www.flickr.com/photos/hyper-world/2401419260/ Boundaries are explicit Services are autonomous Services share schema and contract, not class Service compatibility is based upon policy * http://msdn.microsoft.com/en-us/magazine/cc164026.aspx
- 7. Messaging Patterns * http://www.enterpriseintegrationpatterns.com/toc.html Message Bus is a central place for implementing integration patterns*
- 8. Advantages of Messaging (I) Image source: http://www.flickr.com/photos/renaissancechambara/2288556895/ Loose coupling Separation of concerns Orthogonal architecture
- 9. Advantages of Messaging (II) Testing Scalability
- 10. Disadvantages of Messaging Dependency tracing Who is publishing that message? Is publishing of that message required? Debugging Same as debugging of multithreaded apps Learning curve It’s not a new technology, it’s a paradigm shift Requires different mindset and discipline Image source: http://www.flickr.com/photos/lwr/2257112719/
- 11. Guidelines Consider messaging to loose coupling Avoid RPC across modules/business services/bounded contexts* * In terms of DDD Image source: http://www.flickr.com/photos/rodneytrotter/3323664794/
- 12. Look ahead Messaging is the default communication style for cloud-based services Silverlight does not support synchronous communication out of the box Image source: http://www.flickr.com/photos/bestrated1/2441332480/
- 13. DEMO
- 14. References Composite WPF guidance aka “Prism”, StockTrader RI http://compositewpf.codeplex.com/ StockTrader with messages (revision 12, as shown in demo) http://code.google.com/p/messagingwpf/source/browse/trunk/src/StockTraderRI/ Some OSS messaging frameworks http://code.google.com/p/masstransit/ http://www.nservicebus.com https://rhino-tools.svn.sourceforge.net/svnroot/rhino-tools/trunk/esb/ Fallacies of distributed computing http ://en.wikipedia.org/wiki/Fallacies_of_Distributed_Computing Four tenets of service orientation http://msdn.microsoft.com/en-us/magazine/cc164026.aspx Enterprise integration patterns http ://www.enterpriseintegrationpatterns.com/toc.html