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Using an API Gateway. From Design to Deployment. Also, please look at the new Microservices Solutions page. It discussed the benefits and drawbacks of using microservices and how, despite the complexity of microservices, they are usually the ideal choice for complex applications.

Building Microservices Using an API Gateway | NGINX

This is the second article in the series and will discuss building microservices using an API Gateway. Even though this is a smartphone application, the product details page displays a lot of information. For example, not only is there basic product information such as name, description, and price but this page also shows:. A load balancer routes the request to one of N identical application instances. The application would then query various database tables and return the response to the client.

In contrast, when using the microservices architecture the data displayed on the product details page is owned by multiple microservices. Here are some of the potential microservices that own data displayed on the example product details page:.

In theory, a client could make requests to each of the microservices directly. Each microservice would have a public endpoint https: To retrieve the product details, ptatern mobile client would make requests to each of the services listed above. Unfortunately, there are challenges and limitations with this option. The client in this example has to make seven separate requests.

In more complex applications it might have to make many more. For example, Amazon describes how hundreds of services are involved in rendering their product page. While a client could make that many requests over a LAN, it would probably be too inefficient over the public Internet and would definitely be impractical over a mobile network. This approach also makes the client code much more complex. Another drawback with this approach is that it makes it difficult to refactor the microservices.


Over time we might want to change how the system is partitioned into services. For example, we might merge two services or split a service into two or more services. If, however, clients communicate directly with the services, then performing this kind of refactoring can be extremely difficult.

Because of these kinds of problems it rarely makes sense for clients to talk directly to microservices. It might have other responsibilities such as authentication, monitoring, load balancing, caching, request shaping and management, and static response handling.

It then routes requests to the appropriate microservice. Consider, for example, the product details scenario. An adapter typically handles each request by invoking on average six to seven backend services.

Building Microservices: Using an API Gateway

Rather than having to invoke specific services, pai simply talk to the gateway. This reduces the number of round trips between the client and application.

It also simplifies the client code. It is yet another highly available component that must be developed, deployed, and managed. Otherwise, developers will be forced spi wait in line in order to update the gateway. Only a handful of companies operate at the scale of Netflix and need to handle billions of requests per day. It handles other requests by invoking multiple backend services and aggregating the results.

With some requests, such as a product details request, the requests to backend services are independent of one another. Sometimes, however, there are dependencies between requests. Writing API composition code using the traditional asynchronous callback approach quickly leads you to callback hell.

Others, such as Zeromq, are spi and the services communicate directly.

A system will typically use both asynchronous and synchronous styles. It might even use multiple implementations of each style.

Infrastructure services, such as a message broker, will usually have a static location, which can be facadw via OS environment variables. However, determining the location of an application service is not so easy. Application services have dynamically assigned locations. Also, the set of instances of a service changes dynamically because of autoscaling and upgrades. A later article will describe service discovery in more detail.


This issue arises in all distributed systems whenever one service calls another service that is patfern responding slowly or is unavailable.

However, how it handles the failure depends on the specific scenario and which service is failing. The recommendations could either be empty or replaced by, for example, a hardwired top ten list. Hystrix times out calls that apigef the specified threshold. It implements a circuit breaker pattern, which stops the client from waiting needlessly for an unresponsive service.

If the error rate for a service ali a specified threshold, Hystrix trips the circuit breaker and all requests will fail immediately for a specified period of time.

Hystrix lets you define a fallback action when a request fails, such as reading from a cache or returning a default value. If you are using the JVM you should definitely consider using Hystrix.

In the next article in the series, we will look at communication between services. He now consults with organizations to improve how they develop and deploy applications. He also blogs regularly about microservices at http: Chris Richardson of Eventuate, Inc.

Introduction to Microservices Building Microservices: For example, not only is there basic product information such as name, description, and price but this page also shows: Number of items in the shopping cart Patfern history Customer reviews Low inventory warning Shipping options Various recommendations, including other products this product is frequently bought with, other products bought by customers who bought this product, and other products viewed by customers who bought this product Alternative purchasing options When using a monolithic application architecture, a mobile client would retrieve this data by making a single REST call GET api.

Here are some of the potential microservices that own data displayed on the example product details page: Performance and Scalability Only a handful of companies operate at the scale of Apugee and need to handle billions of requests per day.

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