Sample project demonstrating CQRS & Event Sourcing

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The sample uses the following projects from Jonathan Oliver (https://github.com/joliver)

• EventStore
• NanoServiceBus
• CommonDomain
• StorageAccess

For more information on CQRS and Event Sourcing http://cqrsinfo.com/

To Run The Sample

1. You need to create 3 databases in SQL Server 2008 express:

   • Sample.Subscriptions
   • Sample.EventStore
   • Sample.ReadModel

   On the Sample.Subscriptions table you need to run the lib\NanoMessageBus\SubscriptionStorage.sql to create the table in which NanoMessageBus will store the subscriptions.

2. You need to create 5 transactional Queues in MSMQ:

   • Sample.AppService
   • Sample.Error
   • Sample.Denormalizer
   • Sample.Client
   • Sample.ReadModel

Description of the sample Domain Models implemented:

People

Simple domain consisting of a Person Aggregate Root and two value objects ( PersonName and Address ). The model allows the creation of a person, the MovePerson operation witch changes the address and the kill-ing of a person.

Funds

Sample domain with two ARs, Document and ShareClass and some VOs that demonstrates modeling many-to-many between aggregates. This domain is still work in progress.

A short description of the projects in the sample:

Write Side

1. Sample.DomainModel
	- the domain model for the sample
	- this model is persisted using event sourcing and does not need to handle reads ( queries ) 
	since they are done on the read side.
	- the resulting event stream is the "source of truth" data.

2. Sample.AppService 
	- the handlers for the commands our domain knows to execute

3. Sample.AppServiceHost
	- infrastructure for wiring up the command handlers to NanoServiceBus 
	- this is the actual instance of the service that needs to be running for the write side to process
	commands.

Read Side

1. Sample.ReadModel
	- the read model on witch queries are executed
	- this model should be mapped as close as possible to the views
	- this model can be regenerated from the event stream 

2. Sample.Denormalizer
	- the event handlers for the domain events that are published by the DomainModel on the WriteSide
	- this handlers keep the read model in sync with the event stream
	- a better name for it is welcome

3. Sample.DenormalizerHost
	- infrastructure for wiring up the event handlers to NanoServiceBus
	- this process needs to run for the read side to be updated.

Infrastructure

1. Sample.Messages
	- definitions for commands and events that are handled or published by the Domain Model

2. Sample.Client.Web
	- ASP.NET MVC3 application that demonstrates how to integrate the WriteSide & the ReadSide in an application.

TODO

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• Add more complex objects to the domain
• Review transaction management on integration points
• use ConfOrm for mapping the read model
• Add error handeling/reporting
• Create generic infrastructure to handle message/handler registration in nano message bus
• Add js pooling sample to handle eventual consistency
• Add more inter aggregate communication/operations

Disaclaimer

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This sample's primary purpose is for me to gain experience with Autofac, NanoMessageBus, EventStore and all the other projects involved.