BLUE GREEN DEPLOYMENT (HOT UPGRADE)

In General, Deployment requires make changes to the Production or testing environments. Deployment techniques are different from product to product. Few of them are simple and few of them are complex which are required downtime and customer might get impact due to this. Blue Green Deployment is one of the deployment techniques which are very simple and not risky. This deployment does not required downtime and customer would not get any impact during deployment.

In Blue Green Deployment, We will maintain two sets of deployments one is blue deployment and another one is green deployment. This is not at application level as deployment happen with two different versions of applications in different set of instances.  Here a different version of applications means changes in applications like rolling out small features, bug fixes, enhancements to the customers in incremental basis. Here Application changes should not be at hardware for easy and faster recovery in case of issues with either application or deployment.

Blue Green Deployment Process:

1. Bring up the auxiliary resources required to run your application
• These are things like load balancers and security groups.
  
2. Deploy version 1 of your application 
• All of the traffic from the load balancer goes to this version.
  
3. Create version 2 of your application  
• This usually is different code (new feature, bug fix, etc), but could also be a different instance type or key name.
  
4. Switch traffic from version 1 to version 2
• Here is your blue/green deployment. The traffic going through the load balancer no longer goes to Version 1, it goes to Version 2 instead. 
5. Delete Version 1
   
   •  Once you are happy with how Version 2 is performing, you can delete the resources (instances, etc) that Version 1 was using.