Part 6 – Zuul Gateway in Microservices

Zuul Gateway with Microservices

What have we learned so far,

PART 1 – MICROSERVICES INTRODUCTION – In this tutorial, we discussed what microservices architecture is and how its different from monolithic architecture.

 PART 2 – SCENARIO TO DEVELOP – In this tutorial, we discussed the scenario to develop.

PART 3 – FEIGN CLIENT – In this tutorial, we discussed how feign client simplifies the rest client consumption.

PART 4 – RIBBON CLIENT – In this tutorial, we discussed how ribbon client handles the client side load balancing.

PART 5 – EUREKA NAMING SERVER – In this tutorial, we discussed how Eureka Naming Server is used to dynamically register the services at one place.

What is Zuul?

Zuul is the front door for all requests from devices and web sites to the backend of the Netflix streaming application. As an edge service application, Zuul is built to enable dynamic routing, monitoring, resiliency and security. It also has the ability to route requests to multiple Amazon Auto Scaling Groups as appropriate.

What is the need of Zuul Gateway?

The volume and diversity of Netflix API traffic sometimes results in production issues arising quickly and without warning. Netflix need a system that allows us to rapidly change behavior in order to react to these situations. So they implemented zuul gateway to incorporate these requirements.
Zuul uses a range of different types of filters that enables us to quickly and nimbly apply functionality to our edge service. These filters help us perform the following functions:

• Authentication and Security – identifying authentication requirements for each resource and rejecting requests that do not satisfy them.
• Insights and Monitoring – tracking meaningful data and statistics at the edge in order to give us an accurate view of production.
• Dynamic Routing – dynamically routing requests to different backend clusters as needed.
• Stress Testing – gradually increasing the traffic to a cluster in order to gauge performance.
• Load Shedding – allocating capacity for each type of request and dropping requests that go over the limit.
• Static Response handling – building some responses directly at the edge instead of forwarding them to an internal cluster
• Multiregion Resiliency – routing requests across AWS regions in order to diversify our ELB usage and move our edge closer to our members

Lets implement the Zuul Gateway in our application.

1. Create new project names as zuul-gateway-service

2. Update the file and add below annotations @EnableZuulProxy & @EnableDiscoveryClient

package com.onlyfullstack.zuulgatewayservice;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;

@EnableZuulProxy
@EnableDiscoveryClient
@SpringBootApplication
public class ZuulGatewayServiceApplication {

 public static void main(String[] args) {
  SpringApplication.run(ZuulGatewayServiceApplication.class, args);
 }
}

3. Update application.properties file as below

server.port=8765

spring.application.name=zuul-gateway-service

eureka.client.service-url.default-zone=http://localhost:8761/eureka

logging.level.root= DEBUG

logging.pattern.console= %d{yyyy-MMM-dd HH:mm:ss.SSS} %-5level [%thread] %logger{15} - %msg%n

4. Create a zuul filter which will get all the requests before going to the actual service

package com.onlyfullstack.zuulgatewayservice.component;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.exception.ZuulException;

@Component
public class ZuulLoggingFilter extends ZuulFilter {

 Logger logger = LoggerFactory.getLogger(ZuulLoggingFilter.class);
 @Override
 public Object run() throws ZuulException {

  logger.info("*************##############******** printing logs : ");
  return null;
 }

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

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

 @Override
 public String filterType() {
  return "pre"; // 3 types are available - pre - to execute before processing the request, post- after processing the req and error
 }
}

5. To call any service through zuul gateway, we need to form the url as below
http://localhost:8765/{application-name}/{uri}
so the urls for our account-service and customer-service will be
http://localhost:8765/account-service/accounts/1
http://localhost:8765/customer-service/customers

6. If we hit the urls we will get the output as below

Source Code
Download source code of microservice with spring cloud from below git repository :

Lets go to our next tutorial where we will discuss