Blue Green Deployments


Blue/Green deployments

When implementing continuous delivery for your software one very useful technique is called Blue/Green deployments. It addresses the desire to minimize downtime during the release of a new version of an application to production. Essentially, it involves running two production versions of your app side-by-side and then switching the routing from the last stable version to the new version once it is verified. Using OpenShift, this can be very seamless because using containers we can easily and rapidly deploy a duplicate infrastructure to support alternate versions and modify routes as a service. In this lab, we will walk through a simple Blue/Green workflow with an simple web application on OpenShift.

Before starting

Before we get started with the Blue/Green deployment lab, lets clean up some of the projects from the previous lab.

Step 1

Clean up previous labs

$ oc delete all -l app=jenkins-ephemeral
$ oc delete project cicd-<YOURNAME>

Step 2::Lets deploy an application

To demonstrate Blue/Green deployments, we’ll use a simple application that renders a colored box as an example. Using your GitHub account, please fork the following project.

You should be comfortable deploying an app at this point, but here are the steps anyway:

oc new-project bluegreen-<YOURNAME>
oc new-app --name=green --context-dir=dc-metro-map
oc expose service green

Note that we exposed this application using a route named "green". Wait for the application to become available, then navigate to your application and validate it deployed correctly.

Release a new version of our app and test it in the same environment

What we’ll do next is create a new version of the application called "blue". The quickest way to make a change to the code is directly in the GitHub web interface. In GitHub, edit the dc-metro-map/views/dcmetro.jade file in your repo.


We can change the text labels indicated by name of a color. If you want to change the label for the "Red Line", change line 22 from "Red Line" to "Silver Line". These changes will be easily viewable on the main screen of the application.

Use the same commands to deploy this new version of the app, but this time name the service "blue". No need to expose a new route — we’ll instead switch the "green" route to point to the "blue" service once we’ve verified it.

oc new-app --name=blue --context-dir=dc-metro-map

Wait for the "blue" application to become avialable before proceeding.

Switch from Green to Blue

Now that we are satisfied with our change we can do the Green/Blue switch. With OpenShift services and routes, this is super simple. Follow the steps below to make the switch:

oc edit route green

This will bring up the Route configuration yaml. Edit the element "spec:". On the "to:" "name:" line, change its value from "green" to "blue":

  host: green-bluegreen-<YOURNAME>.apps.<WORKSHOPDOMAINNAME>
    targetPort: 8080-tcp
    kind: Service
    name: blue
    weight: 100
  wildcardPolicy: None
As "Administrator", in the "bluegreen-<YOURNAME>" project,
navigate to "Routes",
and select "green"
In the Route detail page
click on Actions
Edit the Route: change the "spec:" -> "to:" section "name:" from "green" to "blue",
click "Save"


Pretty easy, right?

If you want to read more about Blue/Green check out [this post][2] with a longer description as well as links to additional resources.