A blue/green deployment is part of an application development strategy aimed at reducing downtime and user disruption. Teams can test and roll out various application or infrastructure changes — then slowly transition users over once successful.
Both colors refer to deployment environments, in which the blue environment is the existing production environment and the green environment is a duplicate. Configurations and general setup are identical between both.
How do blue/green deployments work?
We've mentioned how maintaining two environments — blue and green — is essential to setting up this type of deployment. The blue environment continues to receive user traffic, while its green counterpart houses a changed application version of an infrastructure component. This green environment is isolated, which lets developers test a wide variety of changes (of varying magnitude) without impacting live traffic.
While the blue environment operates normally, teams will confirm that any proposed changes in development are working properly. This includes an analysis of capacity, resource usage, security impacts, and feature functionality. Once things are working as expected, it's time to begin transferring live traffic to the green environment. This process happens gradually to prevent downtime until all users eventually transition over.
When done correctly, users won't notice this switch on their end and may continue using the application without interruption.
What makes blue/green deployments useful?
Testing is crucial to ensure application functionality and deliver good user experiences. Blue/green deployments give teams a safe environment to evaluate new features, configurations, and infrastructure setups.
This process helps identify any show-stopping bugs, capacity issues, performance problems, or other issues that may impact availability and security. It's a crucial element of the shift-left testing philosophy, in which testing early and often are essential. By catching any issues, teams can deliver the best application experience possible.
Overall, blue/green deployments give organizations a great way to decommission an old application while gradually bringing users onto the same version. You can reconfigure the blue environment as a new green environment once this switch is completed, rinse, and repeat as needed. And if any changes are found once traffic shifts, teams can roll them back to restore functionality.
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Does HAProxy support blue/green deployments?
Yes! HAProxy Enterprise load balancer lets you split and redirect traffic between blue and green environments, sending requests to green only when that environment passes health checks. You can shift a percentage of traffic at a time and run active/active or active/passive setups on premises, in the cloud, or in containers. With HAProxy Fusion, teams can centrally push these changes across all clusters.
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