Zuul Proxy Server for efficient routing

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Organising the interactions between different services in a modern microservices architecture can be challenging. The Zuul proxy, a gateway service that manages every request and performs dynamic routing for a microservice based applications.

What is Zuul and how it came ?

Zuul is an edge service that offers security, resilience, monitoring, and dynamic routing. It is made to manage all of the routing and filtering required in a microservices architecture and is a component of the Netflix OSS (Open Source Software) stack.

Benefits of Using Zuul

  • Dynamic Routing: Zuul can dynamically route requests to different backend services.
  • Monitoring and Insights: It offers monitoring capabilities to gain insights into traffic and performance.
  • Resiliency: Zuul can handle failover and retry mechanisms.
  • Security: It provides features for authentication and authorization.

Using Zuul with Spring Boot

We start by initializing a spring boot project along with the spring-cloud-starter-netflix-zuul dependency. The dependency in the pom.xml should be like the below:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
</dependencies>

Next we enable the Zuul proxy with the help of @EnableZuulProxy annotation in the main class.

@SpringBootApplication
@EnableZuulProxy
public class ZuulProxyApplication {
    public static void main(String[] args) {
        SpringApplication.run(ZuulProxyApplication.class, args);
    }
}

Finally, we configure the zuul routes in our application.properties file.

zuul.routes.service1.path=/service1/**
zuul.routes.service1.url=http://localhost:8081
zuul.routes.service2.path=/service2/**
zuul.routes.service2.url=http://localhost:8082

Requests from /service1/** and /service2/** are routed to http://localhost:8081 and 8082, respectively, with this configuration.

Assuming we have two microservices running on different ports:

  • Service 1 running on localhost:8081 with an endpoint /hello
  • Service 2 running on localhost:8082 with an endpoint /world

With Zuul configured as above, you can access these services through the Zuul proxy:

  • http://localhost:8080/service1/hello will be routed to http://localhost:8081/hello
  • http://localhost:8080/service2/world will be routed to http://localhost:8082/world

Filters in Zuul

Zuul supports filters that can be used for various purposes like authentication, logging, etc. Here’s how we can add a filter:

@Component
public class SimpleFilter extends ZuulFilter {

    @Override
    public String filterType() {
        return "pre";
    }

    @Override
    public int filterOrder() {
        return 1;
    }

    @Override
    public boolean shouldFilter() {
        return true;
    }

    @Override
    public Object run() throws ZuulException {
        RequestContext ctx = RequestContext.getCurrentContext();
        HttpServletRequest request = ctx.getRequest();
        System.out.println(String.format("%s request to %s", request.getMethod(), request.getRequestURL().toString()));
        return null;
    }
}

With the above filter implemented, let’s assume a client makes a GET request to http://localhost:8080/service1/hello, then we would get an output like the below:

GET request to http://localhost:8080/service1/hello

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