Introduction

A blue/green deployment involves deploying the new application version (green) alongside the old (blue).

A load balancer in the form of a Service Selector object is used to test and redirect traffic to
the new application (green) instead of the old one when verified.

Blue/Green deployments can prove costly due to the need to sustain twice the amount of application resources for the duration of the deployment.

To start this, we set up a service that sits in front of deployments.

For example, the service selector section of the manifest file for a blue deployment for an app called web-app with v1.0.0 looks like this:

Type: Service
Metadata:
 Name: web-app-01
 Labels:
   App: Web-app
Selector:
   App: Web-app
   Version: v1.0.0

And the deployment for Blue Web App:

Type: Expansion
Metadata:
  Name: web-app-01
Specification:
  Template:
        Metadata:
           Labels:
             App: Web-app
             Version: "v1.0.0"

When we want to redirect traffic to the new (green) version of the app,

we update the deployment file to point to the new version v2.0.0.

Type: Service
Metadata:
 Name: web-app-02
 Labels:
   App: Web-app
Selector:
   App: Web-app
   Version: v2.0.0

Expansion for Green App:

Type: Expansion
Metadata:
  Name: web-app-02
Specification:
  Template:
        Metadata:
           Labels:
             App: Web-app
             Version: "v2.0.0"

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