A true story about how we evolved our architecture from a monolithic approach to a distributed system

1. From CRUD to messages
…a true story…

2. Alessandro Melchiori
@amelchiori
alessandro@codiceplastico.co
m
http://melkio.codiceplastico.co
m

3. …il contesto…
• Applicazione “finanziaria”
• Circa 70 (230) utenti
• 137.000+ (1.000.000+) aziende
• 420.000+ (4.500.000+) bilanci
• 38.000.000+ (650.000.000+) voci di
bilancio
• 16.000+ (85.000+) call/mese
• “Pluggato” a servizi di terze parti
• Picchi di lavoro “temporali”

4. PresentationLayer
Service/ApplicationLayer
DomainModel
Storage

6. public interface ICompanyDossierService
{
void CloseCompanyFile(Guid id);
void SetInCharge(Guid id);
void SetAnalysisInCharge(Guid id);
IEnumerable<CompanyDossier> Search(Int16[] statuses, ...);
Guid Save(Guid companyFileId, String description, ...);
void DeleteAttachment(Guid id);
AttachmentStream GetAttachmentStream(Guid id);
...
}

9. ANY PROBLEM?

10. • Logica (mal) sparpagliata
• Contesti non definiti
• Modello “fragile” e poco propenso alle
evoluzioni
• Un unico modello per la lettura e per la
scrittura
• Prestazioni
• UI “generazionalista”

12. An object model of the domain that
incorporates both behavior and data
[Martin Fowler - http://martinfowler.com/eaaCatalog/domainModel.html]

13. Use aggregates as unit of
consistency
across your domain model
Protect your model with clearly
defined bounded context
Eric Evans

14. Use aggregates as unit of
consistency
across your domain model
Protect your model with clearly
defined bounded context
Eric Evans

15. Use aggregates as unit of
consistency
across your domain model
Protect your model with clearly
defined bounded context
Eric Evans

16. A single model cannot be appropriate for
reporting, searching and transactional
behavior
Greg Young

17. PresentationLayer
ServiceLayer
DomainModel
Write storage
Read storage

18. State transition are an important part of our
problem space and should be modeled
within our domain
Greg Young, 2008

20. {
"_id" : {
"BucketId" : "Documents/Type",
"StreamId" : "1",
"CommitSequence" : 1
}
"CheckpointNumber" : NumberLong(9460),
"CommitId" : LUUID("5aeae871-8a94-294a-88b1-b2487e5d88d6"),
"CommitStamp" : ISODate("2013-11-21T14:58:08.500Z"),
"Dispatched" : true,
"Events" : [ {
"StreamRevision" : 1,
"Payload" : {
”Code" : ”SITBNC",
”Name" : "Situazione bancaria”,
“Enabled” : true,
“Metadata” : []
}
}],
"Headers" : {
"who" : "guest",
"when" : "2013112115580858",
"when/ticks" : NumberLong(635206462884868984),
"correlation" : "230b5b33-a2ce-4f7e-aa4e-a885c3f05274”
}
}

21. It’s really become clear to me in the last
couple of years that we need a new building
block and that is the domain events
Eric Evans

22. It’s really become clear to me
in the last couple of years
that we need a new building block
and that is the domain events
Eric Evans

23. PresentationLayer
ServiceLayer
DomainModel
Write storage
Read storage

24. CONTACT CENTER FINANCE
Compute Ratings
Command
Appointment
Reserved

25. class ComputeRatingsCommandActivator :
IConsumer<AppointmentReserved>
{
public async Task Consume(
ConsumeContext<AppointmentReserved> context)
{
// COLLECT INFOS AND INITIALIZE THE COMMAND
var endpoint =
await context.GetSendEndpoint(“MyCommandEndpoint”);
endpoint.Send(command);
}
}

26. CONTACT CENTER
FINANCE
Compute Ratings
Command
Appointment
Reserved
CONSULTANT
Reserve Slot
Command
Appointment
Reserved
Appointment
Reserved

27. class MachineInstance : SagaStateMachineInstance
{
public Guid CorrelationId { get; private set; }
public State CurrentState { get; private set; }
public Boolean ConsultantCommandResponse { get; set; }
public Boolean FinanceCommandResponse { get; set; }
}
class StateMachine : MassTransitStateMachine<MachineInstance>
{
public StateMachine()
{
// MASSTRANSIT’S DSL TO DEFINE SAGA
}
public State Running { get; set; }
public Event<AppointmentActivated>
AppointmentActivated { get; private set; }
public Event<ConsultantCommandExecuted>
ConsultantCommandExecuted { get; private set; }
public Event<FinanceCommandExecuted>
FinanceCommandExecuted { get; private set; }
}

28. GOOD / BAD

29. CONTACT CENTER
FINANCE
Compute Ratings
Command
State Transition
Happened
CONSULTANT
Reserve Slot
Command
Resource
Changed
Resource
Changed
Resource
Changed

30. CONTACT CENTER
FINANCE
CONSULTANT

31. class ComputeRatingsCommandActivator :
IConsumer<AppointmentReserved>
{
public async Task Consume(
ConsumeContext<AppointmentReserved> context)
{
// COLLECT INFOS AND INITIALIZE THE COMMAND
var endpoint =
await context.GetSendEndpoint(“MyCommandEndpoint”);
endpoint.Send(command);
}
}

32. REST (HTTP)
TO THE RESCUE

33. class ComputeRatingsCommandActivator :
IConsumer<AppointmentReserved>
{
public async Task Consume(
ConsumeContext<AppointmentReserved> context)
{
// USE API (MICROSERVICE?) TO COLLECT INFOS
// AND INITIALIZE THE COMMAND
var endpoint =
await context.GetSendEndpoint(“MyCommandEndpoint”);
endpoint.Send(command);
}
}

34. > GET /api/appointments/13
< 200 Ok
< ETag: 686897696a7c876b7e
< Last-Modified: Thu, 05 Jul 2012 15:31:30
GMT

35. > GET /api/appointments/13
< 301 Moved permanently
< Location: http://...

36. DEPLOY?

37. SONO UNA CAGATA PAZZESCA!!!
I MICROSERVICES…

39. WHEN?
Tackling complexity in the heart of software

40. WHEN?
Tackling complexity in the
heart of software