What Is Blue Green Deployment? Meaning, Benefits, and Challenges

Blue-green deployment is a code release model with two different yet identical environments that exist simultaneously – where traffic is gradually moved from one to the other so that an updated environment is put into production and the older environment is retired through a continuous cycle. This article explains the meaning of blue-green deployment, its types, benefits, and challenges. 

What Is Blue Green Deployment? 

Blue-green deployment is defined as a code release model with two different yet identical environments that exist simultaneously. Traffic is gradually moved from one to the other so that an updated environment is put into production and the older environment is retired through a continuous cycle. 

Every day, we witness the launch of new web-based applications and software. From business websites to online video games, all these have backends consisting of the server and database and a front end that makes up the user interface. The process by which these software systems’ activities are made available to the public is known as deployment. 

Software deployment includes all the processes and steps necessary to make an application and its updates available for public access. Many deployment strategies have been developed over the years. One prominent example of deployment strategy is the blue-green deployment. 

Blue-green deployment is a technique for rolling out new software designs or updates without causing downtime, typically used in DevOps scenarios for web app maintenance. It requires two exactly same hardware environments set up for one application. One, called the blue or old version, is the active one and serves end users, while the inactive one is referred to as green. 

When the developers want to release a new feature or version of an app, the update and testing are performed on the inactive green environment. After this, traffic is gradually transferred from the blue environment to the green, and the blue/old environment is made inactive. 

Blue-green deployment was created in 2005 by Daniel North and Jet Humble. These two developers sought a lasting solution to the late production errors found on their e-commerce website. After testing and deploying new updates, they realized some mistakes cropped up. The duo solved this the next time by preserving the older website version and making a new one with the updated features. Running both versions in parallel with the old, always ready to be rolled out in case of technical flaws, made a considerable difference in the user experience. They termed the strategy “blue-green deployment.”

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How Does a Blue Green Deployment Work? 

Blue-green deployment functions using a pretty simple principle. The foundation of this principle is side-by-side deployment, in parallel as opposed to sequential deployment. For blue-green deployment to work, the host developers must have two identical yet separate environments. This ideally means a duplicate copy of every structure from the application server to the graphical user interface to the database system used to store and manage data and every other part of the software system. 

There have been modifications to the initial structure with further advancement and understanding of how one can utilize this blue-green deployment. Still, the core of this deployment strategy remains the same.

In blue-green deployment, two servers are continually maintained. However, only one server is live and fully deployed at any instance in time. This live server is where public traffic comes from the domain name system. The live, blue server is the production server, while the inactive green server is called the staging server. 

To understand how blue-green deployment works, you must understand the stages used in this deployment model.

Stage 1: Duplicating resources

The first step in blue-green deployment involves duplicating all the resources used by a particular application. As mentioned earlier, this involves database management and server management. The database must constantly be kept in sync and updated as the application runs. This can be both difficult and demanding. As such, blue-green deployments can have shared components like the database. 

Stage 2: Updating the server

The next step is updating the dormant server with the web application’s new feature or latest version. An excellent example is adding a new character or level to a video game. It could also include a new color tone and font on your website. Whatever it is, this new feature is hosted on the inactive server and adequately tested for errors. 

Stage 3: Switching traffic to the new server

Deploying the new updated version of an application in a blue-green deployment strategy involves switching existing and incoming traffic from the old to the new. This requires a routing device, which can be a load balancer, a regular or mesh network router, or a web server that redirects all incoming traffic with the same domain name as before. Assuming the blue server is the old green is new, you will have to configure the router to stop sending live traffic to the blue server and direct all new traffic to the green server no matter the time of the day. This way, any immediate error can be seen, and the deployment paused. 

Stage 4: Relegating the blue platform  

Once all users have exited the blue platform, it is relegated to become the inactive server serving as a backup or recovery option. Also, the now inactive server becomes a stage for configuring the next update to be deployed. This process is a continuous cycle in reverse order, with the green server starting as the live one.

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Types of Deployment Explained: Blue Green Deployment and Others 

Since the advent of the web, multiple deployment strategies have been used to improve existing applications. The primary deployment strategies used across the globe include:

1. Blue-green deployment 

As already explained, blue-green deployment is a deployment model where the developing team has two identical hosting infrastructures, one used in production and the other acting as a reserve for contingencies and rolling out future updates. With blue-green deployment, there is easy rollback and no downtime, which is vital for sensitive and widely used applications.

2. Canary deployment 

The canary deployment strategy is a model that involves rolling out releases to a small fraction of users of a particular web app. Just like canaries were used to detect danger in mines, the same way the subset of users can give proper feedback on the new release being deployed before others are exposed to it. The canary deployment method provides an early warning of a failed deployment without impacting most of the user experience. 

Canary deployments are ideal for applications that have a set of users who are more tolerant of bugs. This could include internal employees or a canary group of users who would not mind accessing new features at the risk of possible bugs in the system. One advantage of canary deployment is that there is no need for new infrastructure like in blue-green development. This makes it suitable for smaller, budget-constrained groups. It also provides live updates about a certain feature from multiple points of view. However, canary deployments can be complex and more time-consuming. 

3. Rolling deployment 

Rolling deployment is a deployment model that involves the release of software updates on server subsets gradually rather than updating all the servers at the same time. When using the rolling deployment strategy, users on the older servers use the old version, while users directed to the updated servers can view the latest updates. If no issues are reported with the updated servers, more and more servers can be updated until the entire new version is spread across the board. In the case of reported errors or issues, one can easily redirect the users on those updated servers to the other servers.

Rolling deployments work exceptionally well for organizations with extensive infrastructure and can afford to take some servers down without affecting the overall performance and still handle incoming traffic. Rolling deployment, however, requires proper tech support. Another important aspect of rolling development is ensuring backward compatibility across the server sets. 

4. Recreate deployment or basic deployment 

Basic deployment is the traditional deployment system that simultaneously updates all the servers or nodes for a particular web application. In basic deployment, the server is essentially taken offline, recreated, and hosted to allow users to experience the newly added features. 

By deploying a new version or update to a web application with basic deployment, users of that network will experience considerable downtime. Another disadvantage of the deployment method is that rollbacks are not easily carried out, making it the riskiest deployment strategy. 

If the new version has errors or glitches, it would have to be taken down again, increasing the downtime, and then restructured to the previous version or corrected with no way of knowing how users will interact with the updated version. However, basic deployment is less costly than the blue-green deployment strategy and can be applied to businesses with prolonged off hours where downtime would not be detrimental. 

5. Multi-service deployment 

The multi-service deployment system is one where all the servers in a hosting environment are updated simultaneously but with different new services. This means that different subsets of users will interact with new features of the same application depending on what server they are logged into. 

Multi-service deployment boosts application performance for apps operating with different coexisting versions. This deployment model is a simple and cheap method without having as much risk as the basic deployment. It is also subject to downtime and can be challenging to manage all the different services. The blue-green deployment model, however, provides better risk management plans. 

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Benefits and Challenges of Blue Green Deployment 

The key benefits of blue-green deployment include: 

1. Have a system on standby

Blue-green deployment provides a very reliable system where one server is always on standby in case of system failure. This high level of risk management is a strong selling point for blue-green deployment systems. When a server is live, glitches unrelated to the new updates may occur. It could even be a case of malware or ransomware infiltrating the host servers. 

However, because blue-green deployment necessitates a replica of all infrastructure, the backend developers can easily redirect network traffic to the older version. Thus, the organization is still functional and providing its services while simultaneously fixing the other server’s issues. Like a standby generator, service providers can be confident in a backup plan in case of dysfunction.

2. Roll back to previous versions immediately

Sometimes, suggested new features look better on paper than when fully deployed. Other times they may just not be the fitting addition to a web application or have a coding error causing a glitch in the whole system. With blue-green deployment, it is not only easy to locate the source of the problem early, but it is possible to roll back the older version without much deliberation or planning. Developers can quickly pinpoint the source of a problem and redirect traffic to the older version with a load balancer, giving them time to sort out the problem. 

3. Enable a downtime-free deployment 

Have you ever had to use an app but could not access it? Or received notification of downtime for software or favorite website? That may be discouraging for even a nonessential service. Scaling this up to a financial institution or online marketplace with thousands of transactions going on every hour and the implications of downtime becomes more alarming. 

With blue-green deployment, an organization can altogether avoid predictable downtime. Whether trying to do maintenance checks or actively fixing a recurring problem, users can still be shuttled to the twin model without even being aware. Other models require upgrades to be down at midnight when traffic is minimal; this is inconvenient and may lead to substantial financial losses and customer dissatisfaction. 

4. Achieve automatic and seamless upgrades 

Blue-green deployment allows you to use automation to switch between servers and manage traffic easily. It allows for a very seamless user experience in real-time. Using a load balancer, traffic is slowly and gradually re-routed to a different server. The alternative is forcing users to exit the platform or terminate sessions. Load balancers are programmable and make the job of the developers easier, even if it may take longer to make the transfer completely. 

5. Conduct testing in production

Testing in production involves checking the functionality of a product when it has been hosted live on a server. This is very beneficial as it lets you know exactly how the product functions from the user interface. However, it can be pretty challenging and may lead to a bad customer experience if a bug is encountered before you can fix it. With blue-green deployment, a product can be tested while hosted on the inactive server. 

When you are ready to deploy, there is very little chance of encountering any unexpected glitch, as all those would have been erased in testing without any end user’s knowledge. Production in testing is a benefit of blue-green deployment that allows an organization to maintain a high level of professionalism in the public view. 

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Although blue-green deployment has changed the narrative for web applications, it also has some challenges, which include:

1. Costs

As easy as it may sound, it can be pretty expensive to replicate the entire production environment for an application. It requires twice the amount spent on infrastructure. It may also require more human resources to monitor and operate the inactive servers without a concomitant increase in users. Whether it involves buying more equipment and hardware or more infrastructure in the cloud, blue-green deployment is not the most affordable option for every team of DevOps engineers.

2. Difficulty in scaling 

As the business scales and the users of a web service increases, the existing, once simple infrastructure becomes more and more complex. Every effort has to be doubled to maintain the homogeneity of both environments. 

3. Difficulty in database management 

One of the most challenging aspects of blue-green deployment is the difficulty encountered if the new features alter or interact with the current databases. 

If the application changes the database schema, you must create a hybrid schema that supports the old and new. After switching, you can now eliminate the old schema. For some, managing two different databases and ensuring the viability of both can be very difficult. One way around this includes having both servers rely on just one database infrastructure. 

4. Distorted user transaction 

In the blue-green deployment model, deployment of a new feature or version occurs irrespective of the transactions being done at that time. Transfer of live clients occurs without any pause in functionality. As this traffic transfer is being done, transactions can be aborted or lost. To fix this, users may have to retry the transaction, which can be inconvenient or even impractical regarding financial transactions. 

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Takeaway 

As release cycles get shorter and shorter, developers are under pressure to launch new updates and iterations at regular intervals. The blue-green deployment model helps developers, operations managers, and DevOps teams meet release timelines without compromising code quality. When nearly every app is consumed as a service through a “web application,” blue-green deployment has become a popular option for fast-paced software delivery. 

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