6. Zuul Gateway

6.1 Introduction

• Zuul is the unified gateway to our services

• Whether it's a request from a client (PC or mobile) or an internal call to a service.

• All requests for services go through the Zuul gateway, which then implements authentication, dynamic routing, and so on.

6.2 Getting started with Zuul

Actual path: http://localhost:8081/test

Expected path: http://localhost:10010/api/service/test
		  http://localhost:10010/path prefixed/service name/controller access path			

• Step 1: Import pom dependencies

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

• Step 2: Turn on the zuul service

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

• Step 3: Modify the yml file

  server:
    port: 10010
  spring:
    application:
      name: zuul_demo
  zuul:
    prefix: /api  #Routing Prefix
    routes:
      service: /service/**
        path: /service/**
        url: http://localhost:8081
  

6.2 Routing Oriented

• The yml file writing above kills the access path and changes it to service name access

• Step 1: Modify the pom dependency

  <!--Add to eureka Client-->
  <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
  </dependency>
  

• Step 2: Open the eureka client

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

• Step 2: Modify the yml file, register yourself with the registry, and access it through the service name

  • Once registered with the registry, the service name is automatically accessed through Ribbon, and access paths can be omitted from writing

  server:
    port: 10010
  spring:
    application:
      name: zuul
  eureka:
    client:
      service-url:
        defaultZone: http://localhost:10087/eureka/
    instance:
      instance-id: ${spring.application.name}:${spring.cloud.client.ip-address}:${server.port}
      prefer-ip-address: true
  zuul:
    prefix: /api	#Routing Prefix
  

6.3 Filter

• One of the important functions of Zuul as a gateway is to enable authentication of requests.
• This is often achieved through filters provided by Zuul

6.3.1 ZuulFilter

• ZuulFilter is the top-level parent of a filter, with four methods

  public abstract ZuulFilter implements IZuulFilter{
      		abstract public String filterType(); 	//Filter type
      		abstract public int filterOrder();		//Execution order
      		boolean shouldFilter();					//Is Execution Needed
      		Object run() throws ZuulException;		//Specific business logic
  }
  

  • shouldFilter: Returns a Boolean value to determine if the filter needs to be executed.Return true execution, return false does not execute
  • FiltererType: Returns a string representing the type of filter.There are four types:
    • pre: Request executed before being routed
    • routing: called on route request
    • post: called after routing and errror filters
    • Error: an error call occurred while processing the request
  • FiltererOrder: Defines the execution order of the filter by returning an int value. The smaller the number, the higher the priority.
  • run: The specific business logic of the filter.

  6.3.1 Getting Started with Filters

  • Create a test class and inherit ZuulFilter

    package com.czxy.filter;
    
    import com.netflix.zuul.ZuulFilter;
    import com.netflix.zuul.context.RequestContext;
    import com.netflix.zuul.exception.ZuulException;
    import org.springframework.stereotype.Component;
    
    import javax.servlet.http.HttpServletRequest;
    
    @Component
    public class LoginFilter extends ZuulFilter {
        @Override
        public String filterType() {//  Setting Type
            return "pre";
        }
    
        @Override
        public int filterOrder() {//  Set Sort
            return 1;
        }
    
        @Override
        public boolean shouldFilter() {//  Execute or not
            return true;
        }
    
        @Override
        public Object run() throws ZuulException {
            //1, Get the context object
            RequestContext requestContext = RequestContext.getCurrentContext();
            //2, get the request object
            HttpServletRequest request = requestContext.getRequest();
            //3, get the check request header
            String token = request.getHeader("Authorization");
            //4. Determine if there is any
            if (token == null){
                //4.1 Turn off response
                requestContext.setSendZuulResponse(false);
                //4.2 Return status code
                requestContext.setResponseStatusCode(401);
            }
            //5, Release
            return null;
        }
    }
    

6.4 Load Balancing and Fusing

• Ribbon load balancing and Hystix fusing mechanisms are already integrated by default in Zuul.

  #Gateway Configuration
  zuul:
    retryable: true   #Turn on retry (Note: Check if zuul was configured before, and if configuration requires merging configuration items)
  
  #Global Load Balancing Configuration
  ribbon:
    ConnectTimeout: 250 # Connection timeout (ms)
    ReadTimeout: 2000 # Communication timeout (ms)
    OkToRetryOnAllOperations: true # Whether to retry all operations
    MaxAutoRetriesNextServer: 2 # Number of retries for different instances of the same service
    MaxAutoRetries: 1 # Number of retries for the same instance
  #Fuse
  hystrix:
    command:
     default:
          execution:
            isolation:
              thread:
                timeoutInMillisecond: 6000 # Fuse timeout: 6000ms