Edition 0 Updated to asp. Net core 0

Additional cross-cutting features in an Ocelot API Gateway 
There are other important features to research and use, when using an Ocelot API Gateway, described 
in the following links. 
•
Service discovery in the client side integrating Ocelot with Consul or Eureka
https://ocelot.readthedocs.io/en/latest/features/servicediscovery.html
 
•
Caching at the API Gateway tier
https://ocelot.readthedocs.io/en/latest/features/caching.html
 
•
Logging at the API Gateway tier
https://ocelot.readthedocs.io/en/latest/features/logging.html
 
•
Quality of Service (Retries and Circuit breakers) at the API Gateway tier
https://ocelot.readthedocs.io/en/latest/features/qualityofservice.html
 
•
Rate limiting
https://ocelot.readthedocs.io/en/latest/features/ratelimiting.html
 
•
Swagger for Ocelot
https://github.com/Burgyn/MMLib.SwaggerForOcelot
 

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182 
CHAPTER 6 | Tackle Business Complexity in a Microservice with DDD and CQRS Patterns 
CHAPTER 
6 
Tackle Business 
Complexity in a 
Microservice with DDD 
and CQRS Patterns 
Design a domain model for each microservice or Bounded Context that reflects understanding of the 
business domain.
This section focuses on more advanced microservices that you implement when you need to tackle 
complex subsystems, or microservices derived from the knowledge of domain experts with ever-
changing business rules. The architecture patterns used in this section are based on domain-driven 
design (DDD) and Command and Query Responsibility Segregation (CQRS) approaches, as illustrated 
in Figure 7-1. 

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183 
CHAPTER 6 | Tackle Business Complexity in a Microservice with DDD and CQRS Patterns 
Figure 7-1. External microservice architecture versus internal architecture patterns for each microservice 
However, most of the techniques for data driven microservices, such as how to implement an ASP.NET 
Core Web API service or how to expose Swagger metadata with Swashbuckle or NSwag, are also 
applicable to the more advanced microservices implemented internally with DDD patterns. This 
section is an extension of the previous sections, because most of the practices explained earlier also 
apply here or for any kind of microservice. 
This section first provides details on the simplified CQRS patterns used in the eShopOnContainers 
reference application. Later, you will get an overview of the DDD techniques that enable you to find 
common patterns that you can reuse in your applications. 
DDD is a large topic with a rich set of resources for learning. You can start with books like 
Domain-
Driven Design
 by Eric Evans and additional materials from Vaughn Vernon, Jimmy Nilsson, Greg 
Young, Udi Dahan, Jimmy Bogard, and many other DDD/CQRS experts. But most of all you need to try 
to learn how to apply DDD techniques from the conversations, whiteboarding, and domain modeling 
sessions with the experts in your concrete business domain.