What is Blue-Green Deployment?
Blue-green deployment is a strategy for deploying applications in which old and new versions of the application run side-by-side in two near-identical production environments. The old version is known as the “blue” environment, and the new version is called the “green” environment.
After the test is complete, a router or load balancer reroutes requests to the green environment. Developers can run smoke tests and see if the target environment is working well – if not, they can roll back by rerouting traffic back from the green to the blue environment.
The basic idea of a blue-green deployment is to have two interchangeable production environments. One for the old version and another for staging the new version. These environments might be different virtual machines, physical devices, or operating environments, each with unique IP addresses.
How Does Blue-Green Deployment Work?
In a blue-green pattern, when a new version of the product is ready, the last stage of testing takes place in a green environment. These can be two machines or a single physical machine running separate virtual machines. The two environments sometimes share an IP address, so the split can be separate parts of the web server.
Once developers are confident about the new version, they switch the router to forward all traffic to the green environment. The blue environment is then idle.
Blue-green deployments provide an easy opportunity to roll back quickly. You can always switch back to the previous good environment if something goes wrong. It is possible for the blue environment to process transactions even if the green environment is running – for example, you could set this up by sending transactions to both environments in parallel, with the blue environment acting as a backup.
To reduce the possible issues in a new version, you can switch the application to read-only mode, before making the switch from blue to green, and then switch it to read/write mode.
To provide a seamless experience for users, the two versions (blue and green) are different but should be as similar as possible from the user’s perspective.
This basic process is the same as required for a properly functioning cloud backup system, which is available on standby at any time. You can always test your disaster recovery system on each release to make sure it is working properly. The key here is that you can easily switch between project environments. This can be achieved by changing the web server or the domain hierarchy. Another option is to use one database and make all changes to the domain and web tiers.
Blue Green Deployment Benefits
Improved Incident Response Process
Incident activities often escalate into bigger problems that, if not properly controlled and handled, can lead to negative consequences. These can include data breaches, financial damages, and business disruption. Rapid response to incidents helps organizations mitigate vulnerability exploits, minimize losses, restore processes and services, and decrease the risk of future incidents.
Blue-green deployments use two parallel production-ready environments, so you can rapidly switch to a stable environment if something goes wrong. They reduce the risks inherent in production testing – teams can easily troubleshoot problems and return to reliable production with a simple routing change.
You can temporarily make your application available with read-only access during the transition. Alternatively, you can use a load balancer to implement a rolling transition while waiting for a transaction to be completed in a live environment.
Have a System on Standby
A blue-green deployment provides a highly reliable system, with one server always on standby, ready to take over in the event of a system failure. Because blue-green deployments keep a copy of all infrastructure, backend developers can easily redirect network traffic to the previous version. As a result, organizations can continue to operate and provide services while troubleshooting application and server issues.
Promote Fast Release Cycles
For a product owner working within a CI/CD framework, blue-green deployments are a great way to bring software into production. Software may be released almost at any time, with no need to schedule new releases for weekends or outside business hours. Because there is no downtime involved, these deployments avoid negative impacts on the users.
Blue green deployments reduce stress for DevOps teams. It is not necessary to rush updates during set downtime, which can result in deployment errors during a short maintenance window. Possibly the biggest benefit is zero downtime – even in case of a failed deployment.
Enable a Downtime-free Deployment
Downtime is frustrating for users, even for non-essential services. The impact of downtime becomes even more impactful in mission critical applications, such as systems with thousands of operations or transactions per hour.
A blue-green deployment allows organizations to significantly reduce planned downtime. Whether you are performing maintenance checks or proactively fixing recurring issues in the application, users don’t feel the change.
Conduct Testing in Production
Production testing involves verifying the functionality of the product hosted live on the server. This is very useful because it allows you to see exactly how the product works from a user’s perspective. However, if customer-facing bugs are only discovered by customers in production, this can lead to a poor customer experience. With the blue-green pattern, testing teams can identify issues and resolve them quietly, without the end user’s knowledge.
Conclusion
In this article, I explained the basics of blue green deployment and how it benefit software organizations:
- Improved incident response process—Rapid response to incidents helps organizations mitigate vulnerability exploits, minimize losses, restore processes and services, and decrease the risk of future incidents.
- Have a system on standby—A blue-green deployment provides a highly reliable system, with one server always on standby in case of system failure.
- Rapid releases—With blue-green deployments, software may be released almost at any time, with no need to schedule new releases for weekends or outside business hours.
- Enable a downtime-free deployment—A blue-green deployment allows organizations to significantly reduce planned downtime.
- Conduct testing in production—With the blue-green pattern, testing teams can identify issues and resolve them quietly, without the end user’s knowledge.
I hope this will be useful as you start using the blue-green deployment strategy.
Author Bio: Gilad David Maayan
Gilad David Maayan is a technology writer who has worked with over 150 technology companies including SAP, Imperva, Samsung NEXT, NetApp and Check Point, producing technical and thought leadership content that elucidates technical solutions for developers and IT leadership. Today he heads Agile SEO, the leading marketing agency in the technology industry.
