Introduction to the open source ESB NServiceBus

1. Introduction to NServiceBus Adam Fyles Solution Architect AdamFyles.blogspot.com

2. Why use a service bus? Definition “a software architecture construct which provides fundamental services for complex architectures via an event-driven and standards-based messaging engine (the bus).” – Wikipedia Building Systems vs. Applications System Application

3. The 8 fallacies of distributed computing The network is reliable Latency isn’t a problem Bandwidth isn’t a problem The network is secure The topology won’t change The administrator will know what to do Transport cost isn’t a problem The network is homogeneous Deutsch ‘94, Gosling ‘97

4. Coupling Platform Interoperability matters( Fallacy #8 ) Proprietary vs. Standard protocols Schema & Contract – XML Spatial Server A relies on Server B Can communication continue? Store & Forward Temporal The processing of B affects that of A Request/Response Asynchronous Messaging Linux Windows RPC

5. Scalability & Flexibility Flexibility What about upgrades? What about virtualization? Scalability Scaling Up vs. Out – don’t get stuck with one option The Grid – work distribution

6. Messaging to the Rescue! Communication between services and Endpoints is described by message patterns Durable Flexible Unidirectional – non-blocking Less coupling NServiceBus provides several messaging patterns out of the box, but allows for the composition and/or creation of new patterns

7. Example Rollback Rollback Transaction Queue Order DB Call 1 of 3 Call 2 of 3 App Order is back in the queue

9. IProfile

10. IConfigureThisEndPoint

11. AsA_Server

12. IWantToRunAtStartup

13. IMessage

14. ISpecifyMessageOrderHandling

15. IHandleMessages<T>Configuration Wait for Messages Scan IoC & Dispatch Handlers

16. Generic Host NServiceBus.Host.exe

17. Point to Point 2 Client Bus Server Bus Bus.Send()

18. Point to Point Configuration Client classEndPointConfig: IConfigureThisEndpoint, AsA_Client{ } <UnicastBusConfig> <MessageEndpointMappings> <add Messages="MyMessages“ Endpoint="MyServerInputQueue"/> </MessageEndpointMappings> </UnicastBusConfig> Server classEndPointConfig: IConfigureThisEndpoint, AsA_Server{ } <MsmqTransportConfigInputQueue="MyServerInputQueue" />

19. Point to Point Demo

20. Client Bus Request & Response 3 Server Bus Bus.Send(), Bus.Reply()

21. Publish & Subscribe 5 Subscription Storage Publisher Subscriber Bus Bus Subscriber Subscriber Bus Bus Bus.Publish(), Bus.Subscribe(), Bus.Unsubscribe()

22. Pub/Sub Configuration Subscriber classEndPointConfig: IConfigureThisEndpoint, AsA_Server{ } <MsmqTransportConfigInputQueue=Subscriber1InputQueue" /> <UnicastBusConfig> <MessageEndpointMappings> <add Messages="MyMessages" Endpoint=" MyPublisherInputQueue"/> </MessageEndpointMappings> </UnicastBusConfig> Publisher classEndPointConfig: IConfigureThisEndpoint, AsA_Publisher{ } <MsmqTransportConfigInputQueue="MyPublisherInputQueue/>

23. Pub/Sub Demo

24. Scaling Out

25. Distributor 2 Work Management Distributor Worker Bus Worker Worker Bus Bus

26. Distributor Config <appSettings> <add key="NumberOfWorkerThreads" value="1"/> <!-- queue that the distributor process reads and feeds to workers --> <add key="DataInputQueue" value="nservicebus_distributor_data_bus"/> <!--queue that manages work distribution --> <add key="ControlInputQueue“ value="nservicebus_distributor_control_bus"/> <!-- errors --> <add key="ErrorQueue" value="nservicebus_error"/> <!-- queue that maintains the state(availability) of the workers --> <add key="StorageQueue" value="nservicebus_distributor_storage"/> <!-- relevant for a Serialization of "interfaces" or "xml" --> <add key="NameSpace" value="http://www.MySite.com"/> <add key="Serialization" value="xml"/> <!-- can be either "xml", or "binary" --> </appSettings>

27. Demo

28. Long Running Workflows(Sagas)

29. Saga(Workflow) 22 Are we done yet? State Persistence Main Business Process Sub Process 3 Bus Sub Process 1 Sub Process 2 Bus Bus

30. Saga Configuration Server classEndPointConfig: IConfigureThisEndpoint, AsA_Server{ } <MsmqTransportConfigInputQueue=MySagaInputQueue" /> <UnicastBusConfig> <MessageEndpointMappings> <add Messages="MyMessages" Endpoint="MyDestinationInputQueue"/> <addMessages=“NServiceBus.Saga.TimeoutMessage” Endpoint=“timeoutmanager” /> </MessageEndpointMappings></UnicastBusConfig> <NHibernateSagaPersisterConfig> <NHibernateProperties> <addKey="connection.provider“ Value="NHibernate.Connection.DriverConnectionProvider"/> <addKey="connection.driver_class" Value="NHibernate.Driver.SqlClientDriver"/> <addKey="connection.connection_string" Value="Server=localhost;initial catalog=NServiceBus;Integrated Security=SSPI"/> <addKey="dialect" Value="NHibernate.Dialect.MsSql2000Dialect"/> </NHibernateProperties> </NHibernateSagaPersisterConfig>

31. Summary The Bus architectural style typically prompts more questions What happens if communication fails? How long can it take for a process to complete? What is my process dependent on and what depends on my process? Is ok to lose an order(or other entity)? Is this truly a domain event? NServiceBus provides the plumbing, you must provide the System

32. Thank you Adam Fyles Solution Architect AdamFyles.blogspot.com GitHub.com/afyles NServiceBus.com Credits: Udi Dahan, NSB Author