Insights
The Modern Application Development Lifecycle
Modern application development emphasizes deploying new features and fixing bugs frequently—sometimes multiple times a day. To achieve this, deployment processes must be stable and predictable. This means that end users should not encounter updated versions of the application until those updates are verified to work as intended.
Various deployment strategies are available to ensure seamless updates. Among these, blue/green deployments stand out as a highly effective method.
What are Blue/Green Deployments?
At a high level, the blue/green deployment strategy works as follows:
Blue Group:
Represents the current, stable version of the application.
This group of instances (e.g., containers) is actively serving user traffic.
Green Group:
Represents the updated version of the application.
This group of instances is spun up separately to avoid disrupting the current user experience.
How It Works
Application Updates:
When a new application update is ready, the green group is deployed without interfering with the blue group.
Testing the Green Group:
Before switching user traffic to the green group, tests are run to ensure the new version behaves as expected.
Example: For web applications, an HTTP GET request to an endpoint can validate the green group’s functionality.
Handling Failures:
If the tests fail, traffic remains directed to the blue group, ensuring users experience no disruptions.
Switching Traffic:
If the tests succeed, traffic is gradually switched from the blue group to the green group.
The blue group instances are then gradually terminated.
Key Benefits
Minimized Downtime: Blue/green deployments significantly reduce downtime, often achieving zero downtime deployment when executed correctly.
User Experience: Users are shielded from incomplete or faulty updates, maintaining a seamless experience.
AWS Workshop - Blue/Green Deployments on ECS Fargate
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