EXORCISM“THE PRACTICE OF EVICTING DEMONS OR OTHER SPIRITUAL ENTITIES FROM A PERSON OR AN AREA THEY ARE BELIEVED TO HAVE POSSESSED”

CQRSDISTRIBUTED DOMAIN DRIVEN DESIGN

Classic ArchitectureClient executes interactors

Interactor modifies data and returns ViewModel

Step 1: CQSCommand/Query segregation

Commands - write data, void

Queries - read data

Step 1: CQSpublic class SubmitAction : Interactor{

public ShowLeadViewModel Execute(LeadActionDTO action){

var lead = ExecuteLeadAction(action); var viewModel = BuildViewModel(lead);

return viewModel;}

}

Step 1: CQSpublic class SubmitAction : Interactor{

public void Execute(LeadActionDTO action){

ExecuteLeadAction(action);}

public ShowLeadViewModel GetLeadInfo(long id){

var lead = GetLead(id); var viewModel = BuildViewModel(lead);

return viewModel;}

}

Step 1: CQSpublic class SubmitAction : Interactor{

public void Execute(LeadActionDTO action){

ExecuteLeadAction(action);}

public ShowLeadViewModel GetLeadInfo(long id){

return GetLeadViewModel(id);}

}

Step 1: CQS

Separated Query/Command logic

Commands are executed asynchronously

Queries are executed though a thin read layer

Normalization: 3NF vs. 1NF

lead_id status_id queue_idcontact_i

dcampaign_id

assigned_to_id

1043 1 2 241734 54 108

1044 3 5 241771 78 109

lead_id status queuecontact_name

campaignassigned_to

1043 New WaitYau

SiongSaraya

[03SEP2012]Alex

Delors

1043Contacte

dConverte

dDimas

WijayaGunggo_

CA [060512]Mona

Barbara

Step 2

Write model: 3NF

Read model: 1NF

Step 2

Step 2: Events

Step 2: Events

Multiple projections

Scalable reads

Decoupled storage mechanism

RDMBS, Document store, Key/Value store, plain files (local or S3), Sharepoint List, Lucene, Cloud Search

No need for NHibernate Profiler licenses

Step 2: Events

No reliable source of truth.

Step 3

Step 3: Events History

Step 3: Events History

Every data change is logged

Reliable source of truth

Read model can be regenerated anytime

Write model can be regenerated anytime

Step 3: Events History

Writes are not scalable.

Step 4

Step 4var lead1 = {

“leadId”: 15423,“customer_id”: “zubby@bubby.com”,“events”: [

{ “type”: “lead_created”, “data”: {…}, “date”: “20131216T1242” },

{ “type”: “lead_assigned”, “data”: {…}, “date”: “20131216T1342” },

{ “type”: “activity_created”, “data”: {…}, “date”: “20131216T1432” },

{ “type”: “new_lead_event”, “data”: {…}, “date”: “20131216T1522” },

{ “type”: “activity_created”, “data”: {…}, “date”: “20131216T1432” }

]}

Step 4

Step 4: Event Sourcing

Step 4: Event Sourcing

Infinitely scalable reads

Infinitely scalable writes

Audit data

New business insights form past data

Replay events for debugging and analysis

Retroactive logic changes (=bug fixes)

Lightweight backups

NoSQL

No deadlocks

No DBA

CHEAP!!!!!

CQRS

Commands

Events

Event Store

ViewModels / Projections

Questions?

DDD: Building Blocks

Domain Driven Design

Entity

Aggregate

Repository

DDD: Aggregate

shoppingCart = {“id”: 1234,“items”: [{

{ “product_id”: 123, “amount”: 1, “price”: 10},{ “product_id”: 123, “amount”: 1, “price”: 10}

}]}