NServiceBus Alt.Net 20100511

Building enterprise applications with NServiceBus Andreas Öhlund onsdag den 12 maj 2010

What is a distributed system? “A distributed system is one in which the failure of a computer you didn't even know existed can render your own computer unusable” -Leslie Lamport onsdag den 12 maj 2010

The ﬁrst rule of NServiceBus onsdag den 12 maj 2010

There is NO Service Bus! The ﬁrst rule of NServiceBus onsdag den 12 maj 2010

Well, at least no physical one onsdag den 12 maj 2010

The second rule of NServiceBus onsdag den 12 maj 2010

You DO NOT use synchronous communication The second rule of NServiceBus onsdag den 12 maj 2010

The key to robust communication onsdag den 12 maj 2010

Store and forward onsdag den 12 maj 2010

Request/Response the NServiceBus way Fire and forget X 2 onsdag den 12 maj 2010

The effect of tight coupling Temporal Behavioral onsdag den 12 maj 2010

Communication and coupling onsdag den 12 maj 2010

Coupling NServiceBus style onsdag den 12 maj 2010

Command oriented communication CompleteSaleCommand OnlineSales OrderService onsdag den 12 maj 2010

Sending Messages IBus.Send() bus.Send(new CompleteSaleCommand CreateOrderCommand { ProductId = 123, OnlineSales Quantity = 10 .... }); onsdag den 12 maj 2010

Receiving and processing of messages public class CompleteSaleMessageHandler: CreateOrderCommand IHandleMessages<CompleteSaleCommand> { OrderService public void Handle(CompleteSaleCommand c) { ... } } onsdag den 12 maj 2010

Message Contracts • Versioned by the owner • Regular .Net Assembly • Bound to a input queue • class MyMessage : IMessage onsdag den 12 maj 2010

Throttling the load • Manage trafﬁc peaks • Consumer controls the pace • <MsmqTransportConﬁg NumberOfWorkerThreads="3" /> onsdag den 12 maj 2010

What happens when the load becomes to heavy for one server? onsdag den 12 maj 2010

Scaling with the Distributor onsdag den 12 maj 2010

Building consistent systems • Do we produce predictable results even under failure conditions? • What about non transactional sources? onsdag den 12 maj 2010

Isolate non transactional sources as separate endpoints public void Handle(CompleteSaleCommand cmd) { var order = .... orderRepository.Save(order) smtpClient.Send(new MailMessage{...}) } onsdag den 12 maj 2010

Isolate non transactional sources as separate endpoints public void Handle(CompleteSaleCommand cmd) { public void Handle(CompleteSaleCommand cmd) { var order = .... orderRepository.Save(order) var order = .... orderRepository.Save(order) bus.Send(new NotifyCustomerRequest { smtpClient.Send(new MailMessage{...}) } EmailAddress = customer.Email, Body = “Order conﬁrmation” }); } onsdag den 12 maj 2010

Idempotent “Idempotent operations are operations that can be applied multiple times without changing the result” onsdag den 12 maj 2010

When things go wrong onsdag den 12 maj 2010

Messaging gives you a chance to do better • No more showing the users a WSOD • Messages are replayable • Async communication opens up a crucial windows of time for corrections onsdag den 12 maj 2010

Event oriented communication onsdag den 12 maj 2010

Publish and subscribe • Everyone get’s a copy • Removes behavioral coupling onsdag den 12 maj 2010

Billing BillingService OrderAcceptedEvent Shipping SalesService ShippingService Sales Business events onsdag den 12 maj 2010

Finally a chance to discuss non functional requirements that business people understand onsdag den 12 maj 2010

The mechanics of pub/sub onsdag den 12 maj 2010

Becoming a subscriber bus.Subcribe<IOrderAcceptedEvent>(); onsdag den 12 maj 2010

Publishing bus.Publish<IOrderAcceptedEvent>(x=> { ProductId = 123, Quantity = 10 .... }); onsdag den 12 maj 2010

It’s hard to get it right the ﬁrst time around onsdag den 12 maj 2010

Versioning events using interfaces public interface IOrderAcceptedEvent2 : IOrderAcceptedEvent { string SomeNewProperty{ get;set; } } onsdag den 12 maj 2010

Long running transactions onsdag den 12 maj 2010

Use sagas to model long running transactions public class MySaga : Saga<MySagaData>, IAmStartedByMessages<Message1>, IHandleMessages<Message2> { public void Handle(Message1 message) { // code to handle Message1 } public void Handle(Message2 message) { // code to handle Message2 } } onsdag den 12 maj 2010

Storing state public class MySagaData : IContainSagaData { // the following properties are mandatory public virtual Guid Id { get; set; } public virtual string Originator { get; set; } public virtual string OriginalMessageId { get; set; } } onsdag den 12 maj 2010

Timeouts public void Handle(Message1 message) { this.Data.SomeID = message.SomeID; RequestTimeout(TimeSpan.FromHours(1), "some state"); } public override void Timeout(object state) { // some business action like: if (!Data.Message2Arrived) ReplyToOriginator(new TiredOfWaitingForMessage2()); } onsdag den 12 maj 2010

Configuration Developers: use code Administrators: use config files onsdag den 12 maj 2010

Hosting options • Custom hosting • Website • Smartclient • Commandline • Generic host onsdag den 12 maj 2010

Using the Generic Host public class EndpointConﬁg: IConﬁgureThisEndpoint, AsA_Publisher { } onsdag den 12 maj 2010

Using proﬁles to adapt to different environments onsdag den 12 maj 2010

NServiceBus role in CQRS Style applications onsdag den 12 maj 2010

NServiceBus is opinionated onsdag den 12 maj 2010

Why all these opinions? onsdag den 12 maj 2010

Don’t use messaging for queries • Queries need to return relatively fast • No beneﬁt from the robustness that NSB gives • Use NSB to cache data close and use native apis to get at that data onsdag den 12 maj 2010

The end • www.nservicebus.com • www.udidahan.com/blog • andreasohlund.blogspot.com onsdag den 12 maj 2010

NServiceBus Alt.Net 20100511

by andreasohlund on May 12, 2010

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NServiceBus Alt.Net 20100511 — Presentation Transcript