__2018-07-03-blue-green-deployment-spring-cloud-netflix-en.md

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post	Blue-Green Deployment with Spring Cloud Netflix Stack	weekly-drafts/blue-green-deployment-spring-cloud-netflix	star fork follow	spring-framework spring-cloud ha java tutorial	/blue-green-deployment-spring-cloud-netflix/	en

This guide walks through the process of achieving Blue Green Deployment with Spring Cloud Netflix stack.

Introduction

Blue-Green deployment is a technique used for CI / CD where there are two environments with different versions of the same app deployed and one of the environments is used for production and the second one can be used for the final test phase before sending the real traffic. This approach gives you a way for a rapid rollback if for some reason anything goes wrong.

There are quite few ways to achive blue-green deployment, in this guide I'll describe how to do that using Spring Cloud Netflix stack.

Pre-req

• JDK 1.8
• Text editor or your favorite IDE
• Maven 3.0+
• Spring Cloud CLI

Architecture overview

In our architecture we will have an API Gateway routing all the traffic to the downstream applications, we will be also using Service Registry Design Pattern to enable Client-Side Load Balancing.

Discovery Service

We will be using Spring Cloud Netflix Eureka to solve the Service Registry Design Pattern. The easiest way to have an Eureka Server up and running is installing Spring Cloud CLI, with that in place just run the following command:

$ spring cloud eureka

This command will spin up an Eureka Server running at http://localhost:8761.

Downstream Service

The downstream service is very simple, it only shows which environment the application is deployed, it can be either green or blue.

To create this app I just went to start.spring.io and selected Web and Eureka Discovery as dependency, and then I added the following configuration:

src/main/resources/application.yml

spring:
  application:
    name: bluegreen

eureka:
  instance:
    metadata-map:
      env: green

---
spring:
  profiles: blue

server:
  port: 8081

eureka:
  instance:
    metadata-map:
      env: blue

The configuration above contains two profiles, the default profile is used for the green environment, and blue profile that's used for the blue environment. Another important piece in this configuration is the eureka.instance.metadata-map, it will be used by the API Gateway to route the requests to the correct environment.

To validate the environment just create a controller that returns its deployed environment.

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MetadataController {

    @Value("${eureka.instance.metadata-map.env}")
    private String env;

    @GetMapping("/metadata/env")
    public String env() {
        return env;
    }
}

Now just build and run this application twice, once for each environment.

Build

$ mvn clean package

Green Environment

Run

$ java -jar target/blue-green-0.0.1-SNAPSHOT.jar

Validate

The Green app runs on localhost:8080, to validate its response just request the endpoint that we created above.

$ curl -i localhost:8080/metadata/env
HTTP/1.1 200
Content-Type: text/plain;charset=UTF-8
Content-Length: 5
Date: Tue, 03 Jul 2018 20:10:55 GMT

green

Blue environment

Run

$ java -jar target/blue-green-0.0.1-SNAPSHOT.jar --spring.profiles.active=blue

Validate

The Blue app runs on localhost:8081, to validate its response just request the endpoint that we created above.

$ curl -i localhost:8081/metadata/env
HTTP/1.1 200
Content-Type: text/plain;charset=UTF-8
Content-Length: 4
Date: Tue, 03 Jul 2018 20:12:23 GMT

blue

API Gateway

Summary

Congratulations! You just created a blue green deployment using Spring Cloud Netflix stack.

Footnote

• The code used for this tutorial can be found on GitHub