Using Zuul for Edge Service

Concept Description

API Gateway：

An API Gateway is a server and the only node through which you can access the system. API Gateway encapsulates the internal system architecture and provides APIs for clients.

Zuul

Zuul is a JVM-based router and server load balancer of Netflix. You can use Zuul to perform the following operations:

Certification
Insight
Stress test
Canary test
Dynamic route
Service migration
Offload
Security
Static phase response processing
Proactive/passive traffic management

This section describes how to use Zuul as the API Gateway in the Spring Boot application. For details about Zuul, see Router and Filter: Zuul.

Scenario

Use Zuul as the API Gateway, that is, establishes a Zuul Proxy application. In this proxy application, a unified access of all the microservices is defined, and each microservice is distinguished using a prefix (stipped). This section establishes the ZuulProxy Spring Boot application to demonstrate the API Gateway function.

Precautions

In this section, demos, such as ZuulProxy and ZuulServer, are based on Spring Boot and the Java Chassis framework. For detals, see Integrating Spring Boot into Java Chassis.

Starting Zuul Proxy

This topic describes how to start a ZuulProxy application as the API Gateway. Perform the following steps:

Step 1 Add the following dependency to the POM file.

 <dependency> 
   <groupId>org.springframework.cloud</groupId>  
   <artifactId>spring-cloud-starter-zuul</artifactId> 
 </dependency>
 <dependency> 
   <groupId>org.springframework.cloud</groupId>  
   <artifactId>spring-cloud-starter-ribbon</artifactId> 
 </dependency><dependency> 
   <groupId>org.springframework.cloud</groupId>  
   <artifactId>spring-cloud-starter-hystrix</artifactId> 
 </dependency>
 <dependency> 
   <groupId>org.apache.servicecomb</groupId>  
   <artifactId>spring-boot-starter-discovery</artifactId> 
 </dependency>

Step 2 Add annotations to the main Spring Boot category:

 @SpringBootApplication
 @EnableServiceComb
 @EnableZuulProxy//new Annotation
 public class ZuulMain{
 public static void main(String[] args) throws Exception{
     SpringApplication.run(ZuulMain.class, args);
   }
 }

Step 3 Define a routing policy in the application.yaml file
```
 server:
   port: 8754 #api gateway service port number
 zuul:
   routes: #Routing policy
     discoveryServer: /myServer/** #Routing rule
```
The configuration item in ted indicates that the configuration can be performed based on the actual development environment. For details about the rules for defining routing policies of zuul.routers, see：Router and Fillter: Zuul to control routes in a finer granularity.

Step 4 Define the microservice attributes in the microservice.yaml fiel.

 APPLICATION_ID: discoverytest #Service ID
 service_description:
   name: discoveryGateway #Service Name
   version: 0.0.2 #Service Version
 servicecomb:
   service:
     registry:
       address: http://127.0.0.1:30100  #Service Center registration
   rest:
     address: 0.0.0.0:8082 #(Optional) microservice port number

All the services used in this section use the local service center. For details, see Starting the Local Service Center。

Step 5　 Run ZuulMain Application

Using Zuul Proxy

Before using the API Gateway provided by Zuul, start the microservice provider defined in zuul.routers.

Pay attention to the following points in the microservice.yaml file:

APPLICATION_ID must be the same as that defined in ZuulProxy.
The value of service_description.name must be the same as that of zuul.routers

An example is as follows:

APPLICATION_ID: discoverytest #same as ZuulProxy
  service_description:
    name: discoveryServer #Service name, which corresponds to that of zuul.routers
    version: 0.0.2
servicecomb:
  service:
    registry:
      address: http://127.0.0.1:30100 #Service Center registration
  rest:
    address: 0.0.0.0:8080

The portal for API Gateway is: http://127.0.0.1:8754. All services defined in zuul.routers can be accessed through this portal. The access rule are as follows:

http://127.0.0.1:8754/myServer/***](http://127.0.0.1:8754/myServer/***)

This indicates that HTTP calls [http://127.0.0.1:8754/myServer/*** to switch to the discoveryServer service. For example: “/myServer/101” switches to “/101” of discoveryServer service.

If multiple discoveryServer service (in different versions) exist in the Service Center, Zuul uses the Ribbon policy to transfer the request by default.