After the initial architecture and patterns explanation sections, the next sections explain how to implement API Gateways with Ocelot. The main reason to choose Ocelot for the eShopOnContainers reference application 2.0 is because Ocelot is a .NET Core lightweight API Gateway that you can deploy into the same application deployment environment where you're deploying your microservices/containers, such as a Docker Host, Kubernetes, etc. However it will work with anything that speaks HTTP and run on any platform that ASP.NET Core supports. In addition, there are many other products in the market offering API Gateways features, such as Apigee, Kong, MuleSoft, WSO2, and other products like Linkerd and Istio for service mesh ingress controller features. It is designed to work with .NET Core only and is currently built to netcoreapp2.0. This approach improves the load of your hosts by offloading CPU-intensive SSL termination and other routing duties to the Azure Application Gateway. https://microservices.io/patterns/data/api-composition.html, Azure API Management It's important to highlight that in that diagram, you would be using a single custom API Gateway service facing multiple and different client apps. Client apps need to be updated frequently, making the solution harder to evolve. Figure 4-14. There can be many more cross-cutting concerns offered by the API Gateways products depending on each implementation. A possible approach is to have those services within the Docker host or internal cluster to restrict direct access to them from the outside, and to implement those cross-cutting concerns in a centralized place, like an API Gateway. Usually, an API gateway will do the following: Authentication and Rate Limiting. Consider the following questions when developing a large application based on microservices: Interacting with multiple microservices to build a single UI screen increases the number of round trips across the Internet. This pattern is especially convenient when a client page/screen needs information from several microservices. Ocelot is a lightweight API Gateway, recommended for simpler approaches. APIs agem como a “porta de entrada” para aplicativos acessarem dados, lógica … For more information, see Gateway routing pattern. The gateway provides a single endpoint or URL for the client apps and then internally maps the requests to a group of internal microservices. This case is a pattern named "Backend for Frontend" (BFF) where each API Gateway can provide a different API tailored for each client app type, possibly even based on the client form factor by implementing specific adapter code which underneath calls multiple internal microservices, as shown in the following image: Figure 4-13.1. Cross-cutting concerns such as authentication, load balancing, dependency resolution, data transformations and dynamic request dispatching can be handled in a convenient and generic way. nginx [engine x] is an HTTP and reverse proxy server, as well as a mail proxy server, written by Igor Sysoev. In this example, the API Gateway would be implemented as a custom ASP.NET Core WebHost service running as a container. This isolates the gateway from the rest of the workload, but incurs higher management overhead. Requests aggregation. These features let you enforce flexible and fine-grained quotas and rate limits, modify the shape and behavior of your APIs using policies, and improve performance with response caching. Open Source Microservice & API Management Layer. https://microservices.io/patterns/apigateway.html, API Gateway pattern This fact can impact the client-to-microservice communication, as explained in this section. Often, an API gateway includes a transformation engine to orchestrate and modify the requests and responses on the fly. Kong is a scalable, open source API Layer (also known as an API Gateway, or API Middleware). A direct client-to-microservice communication architecture could be good enough for a small microservice-based application, especially if the client app is a server-side web application like an ASP.NET MVC app. The API Gateway offers a reverse proxy to redirect or route requests (layer 7 routing, usually HTTP requests) to the endpoints of the internal microservices. The previous diagrams showing custom API Gateways running in containers are precisely how you can also run Ocelot in a container and microservice-based application. Maybe you will ask the question, what is API Gateway. When you design and build large or complex microservice-based applications with multiple client apps, a good approach to consider can be an API Gateway. This approach increases latency and complexity on the UI side. Figure 4-12. The smaller the attack surface is, the more secure your application can be. In this approach, each microservice has a public endpoint, sometimes with a different TCP port for each microservice. Importante. When splitting the API Gateway tier into multiple API Gateways, if your application has multiple client apps, that can be a primary pivot when identifying the multiple API Gateways types, so that you can have a different facade for the needs of each client app. With a bit of research I found this awesome package for .net core called Ocelot which is basically a gateway with very simple configuration required. Orquestrando execução dos containers com o docker compose. In this approach, a client app can make requests directly to some of the microservices, as shown in Figure 4-12. Ocelot is fast, scalable and provides mostly all features you consider as mandatory when building an API gateway. This project is aimed at people using .NET running a micro services / service oriented architecture that need a unified point of entry into their system. It would be great to use Azure Functions Proxies for that, but unfortunately it wasn't one of the available choices. If you are building Microservices, you are going to need an API Gateway. You need to be careful when implementing the API Gateway pattern. IBM DataPower Gateway is most compared with IBM API Connect, IBM Integration Bus, Apigee, Mule ESB and NGINX Plus, whereas Microsoft Azure API Management is most compared with Apigee, Mulesoft Anypoint API Manager, Amazon API Gateway, Kong Enterprise and 3scale API Management. The API Gateway Functionality. If not scaled out properly, the API Gateway can become a bottleneck. It can also provide other cross-cutting features such as authentication, SSL termination, and cache. Ocelot is an open-source API Gateway built on ASP.Net Core. It's lightweight, fast, and scalable and provides routing and authentication among many other features. This article belongs to a series of articles that explains the importance of API gateways and how to build them using ASP.net Core. API gateways are an essential part of any microservice-based architecture. Centralização dos logs de serviços em execução com Seq. In a production environment based on a cluster, that URL would map to the load balancer used in the cluster, which in turn distributes the requests across the microservices. - No public GitHub repository available -. Figure 4-13.1 shows API Gateways that are segregated by client type; one for mobile clients and one for web clients. The insights available from an API Management system help you get an understanding of how your APIs are being used and how they are performing. Azure Functions is an event driven, compute-on-demand experience that extends the existing Azure application platform with capabilities to implement code triggered by events occurring in virtually any Azure or 3rd party service as well as on-premises systems. It manipulates the HttpRequest object into a state specified by its configuration until it reaches a request builder middleware where it creates a HttpRequestMessage object which is used to make a request to a downstream service. The API Gateway products usually act like a reverse proxy for ingress communication, where you can also filter the APIs from the internal microservices plus apply authorization to the published APIs in this single tier. Therefore, the API gateway sits between the client apps and the microservices. In this case, when using a product like Azure API Management, the fact that you might have a single API Gateway is not so risky because these kinds of API Gateways are "thinner", meaning that you don't implement custom C# code that could evolve towards a monolithic component. Kong controls layer 4 and 7 traffic and is extended through Plugins, which provide extra functionality and services beyond the core platform. Azure API Management solves both your API Gateway and Management needs like logging, security, metering, etc. Azure Function para envio de emails de notificação dos eventos na aplicação. The API Gateway pattern is also sometimes known as the "backend for frontend" (BFF) because you build it while thinking about the needs of the client app. Eventually, it will be bloated because of those different needs and effectively it could be similar to a monolithic application or monolithic service. In this approach, a client app can make requests directly to some of the microservices, as shown in Figure 4-12. Part 2: Building Simple API Gateways with Ocelot. You might do this functionality by aggregating data from multiple microservices and returning a single set of data, and sometimes eliminating any data in the response that isn't needed by the mobile app. Figure 4-13. Ocelot is a lightweight API Gateway, recommended for simpler approaches. Using a direct client-to-microservice communication architecture. Using multiple custom API Gateways. The reference microservice application eShopOnContainers is currently using features provided by Envoy to implement the API Gateway instead of the earlier referenced Ocelot. But in larger applications you should also go further and create other API Gateways based on business boundaries as a second design pivot. Usually it isn't a good idea to have a single API Gateway aggregating all the internal microservices of your application. Azure Application Gateway and API Management are managed services. What tools integrate with Azure API Management. Since the client app would be coupled to those internal endpoints, evolving the microservices in the future can cause high impact for the client apps. And since it's based on .NET Core, it's cross-platform allowing you to deploy on Linux or Windows. This approach reduces latency, since multiple pieces of data come back in parallel and some UI can show data as soon as it's ready. Healthcheck para monitorar o status dos serviços e BD's. An API Gateway can offer multiple features. It is aimed at people using .NET running a micro services / service oriented architecture that need a unified point of entry into their system. According to Netcraft nginx served or proxied 30.46% of the top million busiest sites in Jan 2018. Cross-cutting concerns or gateway offloading. Depending on the features offered by each API Gateway product, you can offload functionality from individual microservices to the gateway, which simplifies the implementation of each microservice by consolidating cross-cutting concerns into one tier. Because of the API Gateway, the client apps won't notice if the APIs being used are implemented as internal microservices or a monolithic API and more importantly, when evolving and refactoring the monolithic API into microservices, thanks to the API Gateway routing, client apps won't be impacted with any URI change. Within Application Gateway, a path-based routing rule is created that redirects any API requests that contain /externalto the API-M back-end 3. An example of a URL for a particular service could be the following URL in Azure: http://eshoponcontainers.… Moreover, implementation changes in the internal microservices might cause code changes at the API Gateway level. API Management provides the core competencies to ensure a successful API program through developer engagement, business insights, analytics, security, and protection. What happens when the application evolves and new microservices are introduced or existing microservices are updated? When I first started working with this scenario the first question I had was - It turns out the solution is a combination of both and is relatively simple - 1. If you don't have API Gateways, the client apps must send requests directly to the microservices and that raises problems, such as the following issues: Coupling: Without the API Gateway pattern, the client apps are coupled to the internal microservices. O aplicativo de desserviço de referência eShopOnContainers está usando atualmente os recursos fornecidos pelo Envoy para implementar o gateway de API em vez do Ocelotreferenciado anterior.

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