INTRODUCTION TO

NSERVICEBUSAdam Fyles

Solution Architect

AdamFyles.blogspot.com

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

Application

System

The 8 fallacies of distributed computing

1. The network is reliable

2. Latency isn‟t a problem

3. Bandwidth isn‟t a problem

4. The network is secure

5. The topology won‟t change

6. The administrator will know what to do

7. Transport cost isn‟t a problem

8. The network is homogeneous

• Deutsch „94, Gosling „97

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

Windows Linux

RPC

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

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

Example

Transaction

DB

Queue

App

Order

RollbackRollback

Call 1 of 3

Call 2 of 3

Order is back in the queue

Endpoint

NSB Process Flow Overview

Scan /bin for Types

Configuration

Wait for Messages

Scan IoC & Dispatch Handlers

• IWantCustomLogging

• IProfile

• IConfigureThisEndPoint

• AsA_Server

• IWantToRunAtStartup

• IMessage

• ISpecifyMessageOrderHandling

• IHandleMessages<T>

Generic Host

NServiceBus.Host.exe

Point to Point

2

BusClient

Bus

Server

Bus.Send()

Point to Point Configuration

Client

class EndPointConfig : IConfigureThisEndpoint, AsA_Client{ }

<UnicastBusConfig><MessageEndpointMappings><add Messages="MyMessages“ Endpoint="MyServerInputQueue" />

</MessageEndpointMappings></UnicastBusConfig>

Server

class EndPointConfig : IConfigureThisEndpoint, AsA_Server{ }

<MsmqTransportConfig InputQueue="MyServerInputQueue" />

Point to Point Demo

Bus

Bus

Request & Response

3

Client

Server

Bus.Send(), Bus.Reply()

Bus

Publish & Subscribe

5

Subscription

Storage

Publisher

BusSubscriber

Bus

Subscriber

Bus

Subscriber

Bus.Publish(), Bus.Subscribe(), Bus.Unsubscribe()

Pub/Sub ConfigurationSubscriber

class EndPointConfig : IConfigureThisEndpoint, AsA_Server{ }

<MsmqTransportConfig InputQueue=Subscriber1InputQueue" />

<UnicastBusConfig><MessageEndpointMappings><add Messages="MyMessages" Endpoint=" MyPublisherInputQueue" />

</MessageEndpointMappings></UnicastBusConfig>

Publisher

class EndPointConfig : IConfigureThisEndpoint, AsA_Publisher{ }

<MsmqTransportConfig InputQueue="MyPublisherInputQueue />

Pub/Sub Demo

Scaling Out

Distributor

2

Work

ManagementDistributor

Bus

Worker

Bus

Worker

Bus

Worker

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>

Demo

Long Running Workflows(Sagas)

Saga(Workflow)

22

State

Persistence

Main

Business

ProcessBus

Sub

Process

3

Bus

Sub

Process

1 Bus

Sub

Process 2

Are we done yet?

Saga ConfigurationServer

class EndPointConfig : IConfigureThisEndpoint, AsA_Server{ }

<MsmqTransportConfig InputQueue=MySagaInputQueue" />

<UnicastBusConfig><MessageEndpointMappings><add Messages="MyMessages" Endpoint="MyDestinationInputQueue" /><add Messages=“NServiceBus.Saga.TimeoutMessage” Endpoint=“timeoutmanager” />

</MessageEndpointMappings></UnicastBusConfig>

<NHibernateSagaPersisterConfig><NHibernateProperties>

<add Key="connection.provider“ Value="NHibernate.Connection.DriverConnectionProvider"/>

<add Key="connection.driver_class" Value="NHibernate.Driver.SqlClientDriver"/><add Key="connection.connection_string" Value="Server=localhost;initial

catalog=NServiceBus;Integrated Security=SSPI"/><add Key="dialect" Value="NHibernate.Dialect.MsSql2000Dialect"/>

</NHibernateProperties></NHibernateSagaPersisterConfig>

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

THANK YOUAdam Fyles

Solution Architect

AdamFyles.blogspot.com

GitHub.com/afyles

NServiceBus.com

Credits: Udi Dahan, NSB Author