What is Blue-green Deployment, Canary release?


  • Problem:Traditionally, we deploy a new release by replacing the current one. The old release is stopped, and the new one is brought up in its place.
    • The problem with this approach is the downtime occurring from the moment the old release is stopped until the new one is fully operational
    • Having monolithic applications introduces additional problems like, for example, the need to wait a considerable amount of time until the application is initialized.
  • Solution:  variation of the blue-green deployment process. At any time, one of the releases should be running meaning that, during the deployment process, we must deploy a new release in parallel with the old one. The new and the old releases are called blue and green.
    • With the blue-green process, not only that we are removing the deployment downtime, but we are also reducing the risk the deployment might introduce.
    • If we combine the blue-green process with immutable deployments (through VMs in the past and though Docker containers today), the result is a very powerful, secure and reliable deployment procedure that can be performed much more often.
  • If architecture is based on microservices in conjunction with Docker containers, we don’t need two nodes to perform the procedure and can run both releases side by side.
  • a canary release is that it's a partial release to a subset of production nodes with sticky sessions turned on.
    • Similar to a BlueGreenDeployment, you start by deploying the new version of your software to a subset of your infrastructure, to which no users are routed.


 Sources: 
http://stackoverflow.com/questions/23746038/canary-release-strategy-vs-blue-green
http://blog.christianposta.com/deploy/blue-green-deployments-a-b-testing-and-canary-releases/
https://www.javacodegeeks.com/2016/02/blue-green-deployment.html

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